# Kamikaze Mode?



## somanywelps (Jan 25, 2012)

This is known as a contractor bypass.

The motor can handle X current, and the batteries have a current limit too.

When RPM is zero, resistance is theoretically zero, so current is infinite.

Which means either your batteries or motor will explode or ignite in a matter of seconds unless it's a VERY low power system or you only do it for a fraction of a second.

(You need a controller)


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## major (Apr 4, 2008)

McRat said:


> I'm at the Forrest Gump stage here. So bear with me.
> 
> For brush-type motors:
> 
> ...


Hi Rat,

I did this. With the students on the go kart race team. They were in transition from E85 5.5hp Honda engines to battery powered electric for the university competition. So we took a ICE powered kart and put a second sprocket on the axle with a chain to a 4 inch series motor. Two 12V 18Ah PbAcid batteries and a big old Albright contactor. Push button on the steering wheel and diode on the motor. Provided a real good boost. Only used a few times and then the kart went into full electric mode.

Things can work well at 12 and 24 volts up to 100's of amps. Like the cranking motor on your ICE. But the voltage and current levels you seek make such "simple" solutions out-of-the-question. You'd be lucky to get it to work once.

Regards,

major


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## McRat (Jul 10, 2012)

So if I do it, I should have a camera setup so it can get on "World's Dumbest Drivers 22"?

OK, thanks! I won't do that.


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## Ziggythewiz (May 16, 2010)

My new favorite show is called Insane or Inspired. I think this would make for a great segment. 

I had planned something similar as a controller bypass to go past my 120V limit, complete with mad scientist knife switch and all...but I happened to compare my gear ratios with my motor's max RPM and found that my goal (0-60 mph in 2nd) would have blown up the engine.


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## ruckus (Apr 15, 2009)

Ok, bear with me for a second..

Does anybody remember a guy a few years back with a voltage selector that looked like a wwII ship speed selector (all ahead 3/4)?

His setup was called something like 'cheap ev drive' or something.

He drag raced his boat of a car and actually did pretty good using an old 13" series dc or something.

Anyway, if anybody remembers, he had some sort of trick (made with wood from the garage) 'power selector'.

Anyone remember? I'll try to dig up some old pics...

Edit: now I remember it was 'poormansev.com' or something similar. Here is his 'controller' 










You gotta respect that kind of ingenuity...

I can hear Tesseract saying "damn, if only I had thought of that..."


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## PStechPaul (May 1, 2012)

There are high power tap switches (or transformer tap changers), but they're big and expensive. It's probably better to use contactors (and really a controller is the right way to go). Here are some:
http://www.surplussales.com/switches/SWPowerTap.html

Like this:


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## McRat (Jul 10, 2012)

ruckus said:


> Ok, bear with me for a second..
> 
> Does anybody remember a guy a few years back with a voltage selector that looked like a wwII ship speed selector (all ahead 3/4)?
> 
> ...


Problem with that? Wouldn't it drain the batteries unequally, so you'd have have progressively less capacity as the voltage went up? 
In other words, you'd be limited by the capacity available from stage 1?

How about a Poor Man's PWM - 
A small motor spins a drum with many narrow contacts all going to the batteries.
You have multiple brushes you can engage with a lever, staged so they increase the % of ON time. 

Say the drum has 12 contacts. When one brush contacts, it would be 1/12 power, when 2 brushes are down, it would be 1/6, 3 brushes down, 1/4, ... 12 brushes down is full 100% duty.

Hmmm... Too complicated. Like a venier scale on a pair of calipers, the number of brushes is less that the number of contacts. As you rotate the brush collar it goes from no contact, to brief contact, to constant contact in a small rotation of the collar? No, that's not right, but it's close. You can do mechanical PWM.

Put some capacitors on it to smooth it out, and you'd have a ghetto PWM speed control. Mechanical. Current limit would depend on the contacts and brushes.


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## McRat (Jul 10, 2012)

No, the drum with contacts has different lengths of contacts.

You use one big brush that is wide enough to cover two contacts.

The brush collar slides down the rotating contact drum.

At first, nothing.
Then it hits 1 contact per rev
Then 2 contacts per rev, 
Then 3 ...
When it get to the far end of the drum, since the brush is wide enough to hit two contacts, it is always connected, and at 100% duty.


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## Ziggythewiz (May 16, 2010)

McRat said:


> Problem with that? Wouldn't it drain the batteries unequally, so you'd have have progressively less capacity as the voltage went up?


Yeah, shouldn't be difficult. Just calculate how long you'd expect to use each level. and size em accordingly. 1st batt 200 AH, 2nd 175 etc. You just have to get in the ballpack and the floodies will balance themselves to make up the difference (let's face it, if that's your controller you're not running lithium).


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## onegreenev (May 18, 2012)

Poormans EV was setup so the batteries were all used for each voltage setting. The setup was complex but it did work. Takes up lots of space and it has lots of copper connectors and contractors to switch the pack around for each voltage. It works and is pretty basic. Multi speed and multi geared so if you know how to do it right you can really have a good running car. No amperage control. It just uses what the batteries can deliver. 

Pete 

The rotary switch is a good idea but switching while under load will cause the switch to burn and pit during the switch. I have a small rotary switch for my Cushman Truckster. It works and even has reverse but one leg is nearly useless but it did last many years of use. Still works. Full resistor contactor setup and three speeds. Works great. 6, 12 and 24 volt setting.


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## Woodsmith (Jun 5, 2008)

McRat said:


> How about a Poor Man's PWM -
> A small motor spins a drum with many narrow contacts all going to the batteries.


Been done.

SimonRafferty on this forum did it as a controller for his Robot Wars competitor.

I also had a go at a small scale mock up to examine the practicalities and videoed it.


I like the steam punkness of the concept and would love to have the set up in a glass bubble arcing away for all to see.
It isn't really practical for vehicle power levels though, and a lot of work for a low power system.


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## Qer (May 7, 2008)

McRat said:


> So if I do it, I should have a camera setup so it can get on "World's Dumbest Drivers 22"?
> 
> OK, thanks! I won't do that.


 *ROFL*



ruckus said:


> Edit: now I remember it was 'poormansev.com' or something similar. Here is his 'controller'
> 
> 
> 
> ...


Mmmm. Naw. I think we can still motivate why kA has to be handled by a more intelligent controller. 

The problems are two as I see it. The first is that it's very up to the driver to switch voltages at the right time (making it one more thing to keep track of + that shifting at the wrong time will make you either lose the sweet spot or blow up the whole contraption) and the second is that the contactors you'll need won't be cheap (unless you find them on the junk yard of course).

The contactors in the Solitons are for example always switched at no load since switching them at full load would wear them out. They CAN shut down full current in an emergency for safety reasons but it's definitely not good for them in the long run. There IS of course contactors that can handle this kind of currents but, well, the price tag isn't DIY-friendly...



McRat said:


> Problem with that? Wouldn't it drain the batteries unequally, so you'd have have progressively less capacity as the voltage went up?
> In other words, you'd be limited by the capacity available from stage 1?


Yep. That too. Your start current would be a lot lower than it would be with a PWM-controller too since a controller "trades" Voltages for Amps. A dumb switch can't "trade" the same way so the max current from the batteries will be a harder limit.



McRat said:


> How about a Poor Man's PWM -
> A small motor spins a drum with many narrow contacts all going to the batteries.
> You have multiple brushes you can engage with a lever, staged so they increase the % of ON time.
> 
> Say the drum has 12 contacts. When one brush contacts, it would be 1/12 power, when 2 brushes are down, it would be 1/6, 3 brushes down, 1/4, ... 12 brushes down is full 100% duty.


There has been some experimenting with that, but I've never seen anyone complete one in full scale suitable for an EV. My guess (since noone has even reported trying more than small proof of concept models) is that trying to control hundreds of Amps (or some kA) will quickly wear the contact fields out due to arching and that in the end it'll get more expensive and probably a lot less reliable than silicon.


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## Dennis (Feb 25, 2008)

If things do not blow up, then a dragster built with direct connect via a contractor would win against a dragster with a motor controller with current limit. I am not sure anyone has successfully got such at setup working without the consequences of huge plasma fireballs shooting out of the motor's commutator section or battery terminals literally exploding off the batteries.

I had someone ignore my advice of using a motor controller. He had a 48 volt set up and used an Albright sw-200 contactor. When the contactor engaged it literally melted into molten copper in the contact area of the contactor and the motor shot out huge plasma fireballs from the motor's vent shroud that surrounds the commutator side of the motor. The brushes vaporized off the surface of the commutator and some of the commutator bars where fused together. Lucky for him the motor stood still this whole time.


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## PStechPaul (May 1, 2012)

I can see where direct torque control (or current control) is ideal for dragsters because it will instantly compensate for wheel slip and adjust the PWM for maximum acceleration. Without that, using a direct battery connection to the motor (and asssuming a series wound traction motor), it would tend to spin the tires and reach maximum RPM as determined by the voltage and the friction of the tires on the track surface.

With the direct battery connection the only limitation will be the resistance of the conductors and the motor winding and the battery. It might survive a lead-acid battery but probably not Lithium with much higher peak capacity.


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## Qer (May 7, 2008)

Dennis said:


> If things do not blow up, then a dragster built with direct connect via a contractor would win against a dragster with a motor controller with current limit.


Provided the tires can keep the grip on the pavement and that the transmission survives the brutal torque the almost short circuit current will result in and that the pack can survive being near short circuited and the contactor actually manages to make before being burned up in a huge cloud of plasma and that the brushes won't go kablam within seconds and that the driver will be able to keep the car straight when it takes off at an insane acceleration and whatever I've forgotten to mention and ..... 

No. I don't think a dragster using connectors will be able to win against one with a controller, because I think the best case scenario is that it breaks down at the start and the worst case scenario will be that it'll be bolting off completely uncontrollable in a random direction and cause mayhem and chaos.

The only way a contraption like that would be controllable is if it has batteries that sag enough to make the current controllable (did anyone say lead-acid...?) but then it won't win anything...


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## PStechPaul (May 1, 2012)

Also, the tap select contraption seems to have a relatively light gauge wire (maybe #10 AWG) on the arm, and the bolts may be steel, so that will add resistance. Actually if that is a blue barrel crimp connector it may be only #14-#16. A 6 foot loop of #14 wire at 0.0025 ohms/foot has 0.015 ohms which limits the current from a 12 volt battery to 800 amps, which is in the safe range for the battery and motor, but not for the wire. Assuming a locked rotor condition, this is 9600 watts, which would quickly melt the insulation and vaporize the wire within less than 50 mSec (WAG), but if the motor spins within that timeframe it will generate BEMF and reduce the current. Obviously this is a very unsafe and inefficient setup, but its very crudeness may save it from catastrophe. But an otherwise well-designed setup, using heavy cables and a high current contactor, will be able to deliver the sort of current and power to the motor which resulted in its spectacular destruction. 

I want video!


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## Ziggythewiz (May 16, 2010)

It was already posted that the contraption you're referring to was driving contactors, not a traction circuit, so safety and inefficiencies at the selector arm are irrelevant.


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## PStechPaul (May 1, 2012)

OK, that makes a little more sense. Here is the website which shows the schematic and the technique required for using it in drag racing:
http://www.poormansev.com/id24.html

It has a 6V battery which sort of provides an "idle" and then the other batteries were selected 48 volts per click, and not in a series/parallel configuration as suggested.

His latest controller using 2000 amps of resistance wire seems like an incredible waste of power, but I guess it works. And the salt water immersion tank is pretty crazy unless you can use the hydrogen and oxygen it produces without blowing up.

His motives are stated to be that he can't afford a proper size solid state controller, but I think it is more that he understands mechanical and basic electrical principles and perhaps has the parts and materials and tools to put them together for little cost.

But, hey, whatever floats (or tows) your boat!


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## Jamie EV (Oct 3, 2012)

Actually, the guy with the ship's throttle lever is not wasting much energy at all. He's doing something old school and clever. First setting is all batteries in parallel....12 volts.....second setting is 4 strings of batts....24....next setting is three strings.....36....2 strings......48....all series....96 volts and he's flying!

Works perfectly find actually and if he wants to he can add a "slot car" style resister spring to control the intermediate voltage between these settings. So it's like a gear shifter and a pedal....the energy wasted is in teh heat of a resistor spring...but you know 

I've been thinking about making a huge heat sunk resistor spring like that. Could make it out of cheap parts. Yes it's a waste of energy but if you can't afford anything cheaper...it's a solution...also I could use the heat in the cabin in the winter lol. 

Man the heat would be incredible.


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## Jamie EV (Oct 3, 2012)

remember how you squeezed the trigger on your slot car too hard and fast and the car shot off the track? Imagine a full sized car doing that....hellacious!

Has anyone tried a mechanically variable induction gap in a step down transformer to control AC current? So basically like a variac but not actual spark occurs because the field is induced from the large coil to the small?


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## Jamie EV (Oct 3, 2012)

McRat said:


> How about a Poor Man's PWM -
> A small motor spins a drum with many narrow contacts all going to the batteries.
> You have multiple brushes you can engage with a lever, staged so they increase the % of ON time.
> 
> ...



That's almost a good idea. I cannot see it lasting more than a week though. There has to be a simpler way to do that. And more reliable. I'm intrigued.


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## PStechPaul (May 1, 2012)

Jamie EV said:


> remember how you squeezed the trigger on your slot car too hard and fast and the car shot off the track? Imagine a full sized car doing that....hellacious!
> 
> Has anyone tried a mechanically variable induction gap in a step down transformer to control AC current? So basically like a variac but not actual spark occurs because the field is induced from the large coil to the small?


That sounds similar to a saturable core reactor or magnetic amplifier:
http://www.sigmaelectricals.com/map.htm
http://www.ele.utoronto.ca/~lehn/conference_papers/CP16.pdf
http://www.freepatentsonline.com/3703692.html
http://www.freepatentsonline.com/3883836.html

There is also a variable transformer design patented by Peschel which eliminates the sparking and current flow between adjacent turns of the winding:
http://www.patents.com/us-4189672.html
http://www.hipotronics.com/products-high-voltage-test-equipment-oem-peschel variable.htm


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## McRat (Jul 10, 2012)

Jamie EV said:


> That's almost a good idea. I cannot see it lasting more than a week though. There has to be a simpler way to do that. And more reliable. I'm intrigued.


Modern electronics are cheap and efficient now.

But I see the "Venier Speed Control" as mearly an issue with materials, not performance. It should have almost no losses. Kind of like why they still use carburators in racing. They are efficient.

This and a different kind of motor design I'm filing for patents on. Probably a waste of money, but maybe it will have some special application it's the best solution for.


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## Siwastaja (Aug 1, 2012)

McRat said:


> Modern electronics are cheap and efficient now.


This. Absolutely.

A super-duper advanced controller can be complex, but today I'd suggest a simple electric controller for those who want a real cheap ass solution.

For example, something like a 555 PWM generator with variable duty cycle ($1), a optocoupled MOSFET/IGBT driver ($5), gate protection diodes ($1), a large, oversized MOSFET or IGBT module with freewheeling diode ($50-100), and some snubber capacitors ($10).

A simple DC controller is simple. And with today's technology, much better than any electromechanical solution.


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## Jamie EV (Oct 3, 2012)

McRat said:


> Modern electronics are cheap and efficient now.
> 
> But I see the "Venier Speed Control" as mearly an issue with materials, not performance. It should have almost no losses. Kind of like why they still use carburators in racing. They are efficient.
> 
> This and a different kind of motor design I'm filing for patents on. Probably a waste of money, but maybe it will have some special application it's the best solution for.


I agree that in principle it should work. If you used gold commutator on yhour drum, you could do it. There WOULD be losses though. A drum rotating and conducting with a brush would cause arcing and corrosion....mind you a capacitor would probably reduce a large portion of that. I look forward to seeing a design (I'll never steal it or try to patent it...maybe only build it lol).

How about a roller on the comm? The drum would have to spin at quite a high speed to get a good PWM frequency/wavelength. 

I want to build this now...hell of a lot cheaper than an industry controller...


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## Jamie EV (Oct 3, 2012)

I was thinking about who makes a conductively clad roller....would brass work? That would last a long time.


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## Jamie EV (Oct 3, 2012)

what you need is a variable pitch commutator.


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## McRat (Jul 10, 2012)

I'm not worried about anybody using any idea I post on a public website.

I used to do custom ECM (auto computer) programming for diesels, I wrote hundreds of different tunes on the dyno, which were put on thousands of trucks legitimately. Hundreds, if not thousands more "stole" my tuning because I refused to "lock" my tuning to the ECM. If I work on your car, I give YOU the keys, I don't keep them. In the long run, it was good for the diesel hotrodding industry.

I'm a hobbyist who has a full time job, and just dink with things when I get time. We are really busy right now, and SpaceX is one of our customers. You might have seen them today in the news.


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## Jamie EV (Oct 3, 2012)

McRat said:


> I'm not worried about anybody using any idea I post on a public website.
> 
> I used to do custom ECM (auto computer) programming for diesels, I wrote hundreds of different tunes on the dyno, which were put on thousands of trucks legitimately. Hundreds, if not thousands more "stole" my tuning because I refused to "lock" my tuning to the ECM. If I work on your car, I give YOU the keys, I don't keep them. In the long run, it was good for the diesel hotrodding industry.
> 
> I'm a hobbyist who has a full time job, and just dink with things when I get time. We are really busy right now, and SpaceX is one of our customers. You might have seen them today in the news.



I did I think. Too bad about the space jump being delayed.


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## McRat (Jul 10, 2012)

http://www.csmonitor.com/Science/20...tch-SpaceX-launch-anomaly-won-t-scrap-mission

It had an engine turn itself off, but they can still "talk" to that engine. It needs to lose 3 engines before they must abort IIRC.


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## Jamie EV (Oct 3, 2012)

McRat said:


> http://www.csmonitor.com/Science/20...tch-SpaceX-launch-anomaly-won-t-scrap-mission
> 
> It had an engine turn itself off, but they can still "talk" to that engine. It needs to lose 3 engines before they must abort IIRC.


Does that impact your company?


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## McRat (Jul 10, 2012)

Jamie EV said:


> Does that impact your company?


No, we are just a very small piece of the puzzle. We provide inspection services for the complex machined parts. 

But if SpaceX becomes profitable, I imagine we will get a lot more work from them.

DOH! Hijack!!!!


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## Jamie EV (Oct 3, 2012)

Back to ghetto controllers, if I was to go the Mosfet route, I think I would just fly by the seat of my pants and try building one from scratch. I could buy a very reliable PWM controller curcuit for a few bucks on eBay and then I would build a MOSFET bank to be run by it. Seems to me that this cannot be THAT difficult. I wouldn't want anything fancy like high pedal lockout and such...just a basic PWM controlled bank of them. 

I was looking on eBay and I was able to find 17 200v n channels with supposedly 30A each....does that seem like it would be enough current/voltage for a decent controller? It's like 510 amps at 200V....seems ok to me....of course I'd need flywheel diods, resistors capacitors etc etc and I'd need to heatsink and fan the unit but it seems like if you can steal a Mosfet circuit off of the interweb you could pretty much build this.

Am I naive?


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## Siwastaja (Aug 1, 2012)

Jamie EV said:


> I could buy a very reliable PWM controller curcuit for a few bucks on eBay and then I would build a MOSFET bank to be run by it. Seems to me that this cannot be THAT difficult.


In theory, it is very easy. In practice, it's easy enough but with a few considerations...



> I was looking on eBay and I was able to find 17 200v n channels with supposedly 30A each....does that seem like it would be enough current/voltage for a decent controller? It's like 510 amps at 200V....seems ok to me....


Nope -- the problem is that switching inductive loads creates large voltage spikes that kill the mosfets. There are two ways around this and _both_ are needed:
1) Overrating of the voltage. If you make a 200V controller, use at least 400V MOSFETs. Preferably 600V. (Consider also IGBTs. 200V is a borderline between MOSFET vs. IGBT in my opinion.)
2) Make sure your freewheeling diodes are quick. Include low-inductance snubber capacitors near the mosfet in the DC bus.

In addition, make the gate drive strong. If you use an Ebay PWM controller, make sure it is a push-pull type. It probably isn't. I would recommend ACNW3130 as a driver. It's not too expensive. Read the datasheet for tips. Then read link given in this post: http://www.diyelectriccar.com/forums/showpost.php?p=324076&postcount=80

Google around - you will find a lot of power electronic design information. Application notes from the semiconductor manufacturers, and forum discussions.

You already addressed heatsinking etc.

Keep the switching frequency low enough - it helps with switching losses if your gate drive is lacking. A few kHz maybe.

Get or borrow an oscilloscope somewhere to actually look at the signals. Use lower voltages first and monitor the voltage spikes so that you won't kill the "expensive" mosfets/igbts in the first tests.



> Am I naive?


I don't think so. Of course this needs some work, but so will any electromechanical solution, too, and with the electrical route, you also have real future if you want to learn more and go further. Also, the power semiconductors get better and better every day, even now. Also, you get real experience and knowledge in power electronics by actually trying the stuff. After you get the basics down, sky's the limit. 

This is my personal opinion but as a disclaimer I have to say that I've been practicing electronics for a long time, so if you are very mechanically-oriented person, your mileage may vary...


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## Jamie EV (Oct 3, 2012)

Siwastaja said:


> In theory, it is very easy. In practice, it's easy enough but with a few considerations...
> 
> 
> 
> ...


Good tips. Lots of studying to do if I chose this method.

I was actually thinking of using a 96 volt system so 200V was pretty much overkill. THey had 600 V mosfets on eBay as well...but I liked the amperage of the 200v ones. Less needed to parallel (or so I figured).

Should I not be more concerned with amps than volts? Presumably one coujld make a monster bank of Mosfets (or IGTB) to switch 1000 to 2000 amps....that might be a lot of soldering but hell it if could make a drag racer...would be what the OP has in mind I think. (Also, he could limit it for street use with the flick of a switch?)


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## Siwastaja (Aug 1, 2012)

Jamie EV said:


> Should I not be more concerned with amps than volts?


You should be concerned about both, but overvoltage is often harder to estimate. If the voltage limit is exceeded, it's just a quick zap and it's dead. This is why I recommended absolute minimum of 2x rating, or preferably 3x rating, as the inductive spikes are not infinite in voltage, and even a bad snubber can limit them somewhat. This is the easier route. On industrial scale, they can spend time and take measurements and fine-tune their snubbers etc. so they can live with only 1.5x overrating the component voltage.



> Presumably one coujld make a monster bank of Mosfets (or IGTB) to switch 1000 to 2000 amps....that might be a lot of soldering but hell it if could make a drag racer...would be what the OP has in mind I think. (Also, he could limit it for street use with the flick of a switch?)


Yeah. Just keep in mind that the more mosfets / larger mosfets, the stronger driver you will need - or multiple drivers.

_In reality_, mosfets and IGBTs are actually not voltage controlled, they are _charge controlled_. This means you need to supply current to change their state. To do this quickly, you need a lot of current in a very short time.

But, everything reduces to a few basic points:
1) Low-inductance DC bus - two closely-spaced wires/plates
2) DC bus decoupling - low-inductance capacitors in the DC bus near the switching elements. High-voltage rated film capacitors as near as possible, and then electrolytics next to them.
3) Gate clamping - diodes from gate to ground and gate drive voltage to "eat away" any coupled overvoltage in gate. Because even if your MOSFET can withstand 600V between Drain-Source, it won't withstand more than 20V between Gate-Source.
4) Strong, _optocoupled_ gate driver with proper gate resistor (about 10 ohm for 2 A drive)
5) Snubbers. Still seems a bit like black art to me, many different choices. Need to be tested in practice. I have used simple RC snubbers.


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## Jamie EV (Oct 3, 2012)

A few basic points, huh? (He says as he tries to digest what you wrote)...ok so a little more complex than I thought. I suppose that's not impossible...

that electromechanical commutator drum is starting to sound good to a caveman like me.


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## Qer (May 7, 2008)

Siwastaja said:


> For example, something like a 555 PWM generator with variable duty cycle ($1), a optocoupled MOSFET/IGBT driver ($5), gate protection diodes ($1), a large, oversized MOSFET or IGBT module with freewheeling diode ($50-100), and some snubber capacitors ($10).
> 
> A simple DC controller is simple. And with today's technology, much better than any electromechanical solution.


Yep. You then put that in a car with a Lithium pack on 100-150 Volt, a matching motor, switch the ignition on, press the throttle and watch your MOSFETs create a wonderful little mini-4:th of July.

Building a controller from scratch is fun, but it sure is expensive! And potentially explosive!



Jamie EV said:


> Am I naive?


Yes.


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## Jamie EV (Oct 3, 2012)

Qer said:


> Yep. You then put that in a car with a Lithium pack on 100-150 Volt, a matching motor, switch the ignition on, press the throttle and watch your MOSFETs create a wonderful little mini-4:th of July.
> 
> Building a controller from scratch is fun, but it sure is expensive! And potentially explosive!
> 
> ...


With the likelihood of controllers exploding in a cloud of igtb sparks, it's a wonder you're all not carrying spare roller/commutator mechanical controllers in the trunk (just in case)!


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## Qer (May 7, 2008)

Jamie EV said:


> With the likelihood of controllers exploding in a cloud of igtb sparks, it's a wonder you're all not carrying spare roller/commutator mechanical controllers in the trunk (just in case)!


No, if you have a system that guarantees the transistors are constantly within specs the risk that they will blow up is pretty low. Unless you don't have a bad connection or some other weak points it's practically zero. There are silicon based high power systems that's been running just fine for decades because they've been very carefully crafted.

Throwing a random 555-based PWM-circuit bought on e-bay together with a handful of MOSFETs in a box and calling it a controller isn't the art of craftmanship. It's the Paul Zigouras way, the art of disaster.

Look him up here in the forum. Lots of enjoyable reading if you're into pain and suffering. Thankfully no one has been wounded or killed. So far...


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## Jamie EV (Oct 3, 2012)

Qer said:


> No, if you have a system that guarantees the transistors are constantly within specs the risk that they will blow up is pretty low. Unless you don't have a bad connection or some other weak points it's practically zero. There are silicon based high power systems that's been running just fine for decades because they've been very carefully crafted.
> 
> Throwing a random 555-based PWM-circuit bought on e-bay together with a handful of MOSFETs in a box and calling it a controller isn't the art of craftmanship. It's the Paul Zigouras way, the art of disaster.
> 
> Look him up here in the forum. Lots of enjoyable reading if you're into pain and suffering. Thankfully no one has been wounded or killed. So far...




So far I've heard lots of good reviews about Paul and Sabrina's controller.


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## Jamie EV (Oct 3, 2012)

Back to what the OP was suggesting, we want a cheap and dirty PWM controller. I really like the idea of the electromechanical one...even if there's a lot of loss through sparks and heat since it attempts to preserve the torque at low and high speeds. (and because theoretically we could build it very cheaply)

So I was thinking about the rotating drum idea and decided it's unnecessarily complicated and large. How about playing the PWM tune like a....record player? (or hard drive for the youngsters)

Imagine a PCB disc spinning with a 12 volt motor from ignition switch....(we would of course have to have a safety interlock that would not switch batt power unless turntable DC motor was spinning. (I think a 567 tone decoder gate could do that...if 567 stops getting chopped signal from disc then it won't close contactor....neato!) That way if motor seizes all of a sudden, you won't get a 100% battery to motor situation and go rocketing off a cliff. (Also, maybe if the brake is pressed, contactor immediately opens as well....for obvious reasons)

Then the only difficulty is to connect the battery terminal (poisitive or negative?) to the wheel with a brush and also the motor side to the brush on a spring-loaded record player arm sort of deal. When you are off the pedal, the arm/brush is located in a copper-free section of the disk.....then as you press the pedal down....the arm swings to a series of narrow copper lines....and as you keep pressing down, it mowes to fatter lines.

My only concern is the exact copper pattern on the wheel. I bet you could etch a regular copper clad board (perhaps a heavy duty one about the size of an old 45 record). 

I would vent the disk and include a fan on the turntable as well as a vented box for it all.

It is a little insane but with sufficient safety protocols, I think it would work.

Disks would wear out but you could print and etch new ones rather cheaply...


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## Jamie EV (Oct 3, 2012)

alternatively you could use a solid piece of copper and paint resist or epoxy on it to create an inverse "off" pattern.


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## Ziggythewiz (May 16, 2010)

Jamie EV said:


> Disks would wear out but you could print and etch new ones rather cheaply...


So I guess you'll measure acceleration in RPM? (disk Replacements Per Minute)


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> So I guess you'll measure acceleration in RPM? (disk Replacements Per Minute)


lol perhaps. How long would a piece of PC board last in that situation? I don't rightly know...

I just sketched an encoder wheel etching pattern. I think I want to build this. Think about it! All of the complexity of a MOsfet circuit replaced by one copper flywheel. It's sort of elegant in it's simplicity.

Sure there are losses at the brushes.. Two in all One for the battery (plus or minus) and one for the motor....but then there are losses in a MOsfet circuit...I don't know how they would compare.

If you wanted to be a bit more reliable, you could instead use a rotating stator coil interupted by a screen to induce a current in a winding....essentially a frictionless version...


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> So I guess you'll measure acceleration in RPM? (disk Replacements Per Minute)


How long does the comm and brushes last on a motor? Years? I don't see this as any different...


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## Jamie EV (Oct 3, 2012)

RPM of the disk would remain constant. The PWM would come from the throttle cable shuttling the brush arm closer to the center of the encoder wheel. This will decrease the "off" cycle until there's a dead short. 

You wouldn't even need high RPMs on the disk. since the hertz would be measured by the number of contacts. My sketch has about 16 so that means 1 rpm is 16 hertz. If I turned the disk at 300 rpm (slow) that would result in 4.8 kHz frequency. 

What's an ideal kHz for PWM?


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## Ziggythewiz (May 16, 2010)

Jamie EV said:


> How long does the comm and brushes last on a motor? Years? I don't see this as any different...


It's very different. The brushes are always touching at least one comm bar and they're made from very robust material that can take some sparking. Your disk would be trying to do what contactors are only made to handle under extreme (sometimes single-use) circumstances, with printed copper that is not made to handle amps, sparks, or heat.


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> It's very different. The brushes are always touching at least one comm bar and they're made from very robust material that can take some sparking. Your disk would be trying to do what contactors are only made to handle under extreme (sometimes single-use) circumstances, with printed copper that is not made to handle amps, sparks, or heat.


I'm fairly certain that motor comms spark and arc. Quite a lot actually. Don't forget that when you reverse a field there's a residual charge that unduces into the comm and causes resistance. 

You might be right about the PCB not being stern enough material...what are comms made of again? Copper? Brass? perhaps it's merely thickness of comm material that's the issue.

there will definitely be some scorching. Much of this has to do with the way the brush addresses the contact. Perhaps there's a way to minimize the resistance. A larger brush perhaps.


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## Jamie EV (Oct 3, 2012)

I've got my thinking cap on....best to clear the area for safety


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## Jamie EV (Oct 3, 2012)

God I'm an idiot! I just figured it out. Ruckus was correct in his initial statement. You make a drum....(a long commutator shaft really) but you don't vary the contact width or any such thing. All you do is have a series of copper/carbon brushes constantly in contact with the comm. THen, you have the leads of each brush in series with a relay (contactor) that can carry say 200 amps (as that's the limit of any good brush/commutator union). When you push the pedal, you close the relays one by one, cumulatively until you get them all closed and cause all power on all the time. Totally saf so long as your throttle pedal doesn't jam (like in an ICE).

In FACT, (and you'll like this one Ziggy), you can use a stock comm! Screw the home made crap. Just use a stock comm, connect all the comm leads to the same point so they all mean contact... and you can do it all with relays. Sure there's friction wear but carbon brushes are easily replaced. 

Ok, try to poop on THIS ONE!


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## Qer (May 7, 2008)

Jamie EV said:


> Ok, try to poop on THIS ONE!


No, no. Sounds like a challenging plan. Please build it and we can compare notes afterwards.

Please video film your experiments.


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## Jamie EV (Oct 3, 2012)

Qer said:


> No, no. Sounds like a challenging plan. Please build it and we can compare notes afterwards.
> 
> Please video film your experiments.


You expect an explosion or death, don't you! 

Yes it would be challenging. From a technical standpoint, the offset brush idea is fine....but then I ran into the fact that the throttle needs to switch the current from each brush...and those relays/switches are not cheap either....so when it's all said and done....it's not as "poor man's" as it could be. Still cheaper than a 1500 dollar zilla 1 K mind you.

got any insights into a throttle cable actuated switch array? Trimmer pot won't work in this case. Got to be able to switch about 5 brushes (I picked 5)....probably 100 amps each.

I was thinking about normally open toggles. But the best I could find was like 20 amp ones.


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## Jamie EV (Oct 3, 2012)

maybe that boat lever from poorman


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## Ziggythewiz (May 16, 2010)

Jamie EV said:


> probably 100 amps each.


How are you controlling these amps? How does the battery hear "Send only 100A please" to each brush?


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## Siwastaja (Aug 1, 2012)

Well, this topic is about "kamikaze" style controllers, so I was simply stating that by overrating some components and taking the risk of occasional breakdown, you can also do electronic control very simply without high-level knowledge. I didn't want to make it sound too difficult, so I listed solutions instead of problems. Of course there are things to do and problems to solve. But it's the same with electromechanical!

But I think your way of taking a readily available DC motor commutator with high-quality brushes is right. It is just too difficult and tedious to build from scratch unless you are really good in machining and you have the tools. Otherwise, it would quickly get over the difficulty of doing a _real_ electronic controller.

If you decide to go the electric way, download free LTSpice and do some simulations first; it has very realistic simulation models for components and it simulates breakdown. This way you don't need to waste money on real components in the first tests.

When reading these posts, don't forget to consider who are saying these things. People who make their living by building very high-quality electrical controllers may have a different viewpoint from those who just want to experiment with ugly cheap-ass solutions . Nothing wrong in that and I understand that viewpoint pretty well.

But I guess the important question here is; do you want to just get some cheap-ass controller done or do you want to learn?


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## Jamie EV (Oct 3, 2012)

There are too many damned finicky things in this setup. It COULD be done. I just don't know if I would bother. DIY is great but it is a pain.


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## Jamie EV (Oct 3, 2012)

Siwastaja said:


> Well, this topic is about "kamikaze" style controllers, so I was simply stating that by overrating some components and taking the risk of occasional breakdown, you can also do electronic control very simply without high-level knowledge. I didn't want to make it sound too difficult, so I listed solutions instead of problems. Of course there are things to do and problems to solve. But it's the same with electromechanical!
> 
> But I think your way of taking a readily available DC motor commutator with high-quality brushes is right. It is just too difficult and tedious to build from scratch unless you are really good in machining and you have the tools. Otherwise, it would quickly get over the difficulty of doing a _real_ electronic controller.
> 
> ...



No I am not taking the criticisms in a bad way...they are all super helpful...if a bit deflating lol! You know when it comes down to price of the electro-mechanical and the MOsfet/IGTB....it almost comes out in the wash. The heavy duty electro stuff is pricey too...and the components for the electronic are also pricey once you factor them all in...

there's certainly no free lunch. I think I could do a Mosfet if I really over-built it and included the snubbers etc...or I COULD do a spinning armature PWM....I think the spinning armature PWM is a tad cheaper but it has safety concerns.

Would be a fun project though. We'll see what I decide to do. I'm going to research tried and true SIMPLE PWMs first.


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## Ziggythewiz (May 16, 2010)

I think the easiest way to do Kamikaze mode is to get a cheap low voltage controller and let that handle the initial ramp-up, then throw a mad scientist knife switch (or contactor) that connects the rest of your pack. I don't know how long the controller would last, but if it's cheap enough, who cares?

Standard disclaimers: fuses, empty road, etc, etc, apply.

I know some guy did this, and I was looking into it, but realized my goal (55 mph in 2nd using 144V w/120V controller that only gets to 45 mph in 2nd) was approx equal to my motor's disassembly point.


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## Tesseract (Sep 27, 2008)

Siwastaja said:


> ...When reading these posts, don't forget to consider who are saying these things. People who make their living by building very high-quality electrical controllers may have a different viewpoint from those who just want to experiment with ugly cheap-ass solutions . Nothing wrong in that and I understand that viewpoint pretty well....


Where did Qer mention that one should buy a specific controller?


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## Siwastaja (Aug 1, 2012)

Tesseract said:


> Where did Qer mention that one should buy a specific controller?


Absolutely nowhere, and yes, all viewpoints are very much needed.


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## PStechPaul (May 1, 2012)

I doubt this project will come up with anything really practical, but if you want to give it a go, here is an idea:










There are six sets of brushes, AA, BB, .., FF, and a commutator consisting of a single copper bar which rotates continuously. The brushes are connected together with conductive flexible wire, like copper braid, and are normally held off the commutator with springs. In the top view, A band is pushing the brush set AA onto the commutator and it provides a PWM of about 17%. When the brush assembly id rotated 90 degrees, as in the bottom view, brush sets BB, CC, and DD are pushed onto the commutator, and a PWM of 67% is produced. You can get 6 different PWM duty cycles with a 0-180 degree rotation of the brush assembly.

I found other ideas for mechanical PWM:
http://www.overunity.com/10061/mechanical-pwm-timed-via-rotary-moment/
http://www.diyelectriccar.com/forums/showthread.php/mechanical-pwm-46258.html

Also look at adjustable dwell cam switches. Here are seome links:
http://www.candycontrols.com/CandyLiterature/CANDY SWITCH.pdf (6 MB PDF)
http://www.precisionmechanisms.com/cs601.htm
http://www.freepatentsonline.com/4112265.html
http://www.scribd.com/doc/36225596/Mechanisms-and-Mechanical-Devices-Source-Book (interesting mechanical designs)


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## Qer (May 7, 2008)

Siwastaja said:


> People who make their living by building very high-quality electrical controllers


If I had a dollar every time someone claimed it was possible to make a living by building very high-quality controllers to DIYers I'd at least come a wee bit closer to minimum wage at least. It's a nice story, but the truth contains a lot less glamour.

No, I doubt anyone makes a living on products to the DIY-market. I certainly am not. I make a living on writing software for chain saws at the moment (true story, even those have software these days), the money I get from the controller sales is a nice perk but it's far from a living.



Siwastaja said:


> may have a different viewpoint


It's called "experience". Been there, blown that.


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## Jamie EV (Oct 3, 2012)

PStechPaul said:


> I doubt this project will come up with anything really practical, but if you want to give it a go, here is an idea:
> 
> 
> 
> ...


Interesting! How are you moving the brushes in and out?


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## Jamie EV (Oct 3, 2012)

I think I would move away from actually moving the brushes or the drum. These elements should probably stay exactly as they are....less finicky that way....but what yhou COULD do is just either connect to the brushes A +B +c+d+e using relays or contactors....or (a knife switch type deal...) 

I think this would probably get you a more reliable and essentially equally efficient setup.

I also thought that instead of varying the brushes that connect, I could vary the speed of the rotating drum....with a PWM (single one on the drum's rotating motor) and control that with the pot box and throttle cable....the only thing about that is that the base speed must be there or the whole thing could end up landing in the closed position and then stop turning...creating hilarity in the process)

Here's a thought. Ignition key activates the spinning drum and aarms the contactor (but does not close it) Throttle cable has a read switch on it so that zero tension equals an open main contactor....if you press on the pedal it triggers the reed and then in turn closes the contactor at a base rpm of say 500 or so....then as you pull throttle further, it turns the pot and pwm control speeds up the DRUM motor and the main motor gets more available pulse width and so on until you have a closed circuit.


I think that solves all the major technical issues....and I didn't have to futz around with turntables or brush wear etc....


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## Tesseract (Sep 27, 2008)

Siwastaja said:


> Absolutely nowhere, and yes, all viewpoints are very much needed.


So far Qer's viewpoint is the only one that isn't divorced from reality... 

...because mechanical PWM is dumber than a box of rocks.

The first problem is that it controls duty cycle directly. Please consider for a moment what would happen if you slammed the "throttle" to maximum on one of these Rube Goldberg-like contraptions. Here's a hint: a series DC motor at a dead stop looks more or less like a short circuit.

The second problem that none of you engineering geniuses seemed to have considered is that there is no pathway for freewheeling current during the off time of the mechanical switch. Guess how long the contact surfaces are going to last with you repeatedly interrupting huge amounts of current through an inductor with them?

Finally, this idea has been hashed over here numerous times before and I have stomped it death several times myself:

http://www.diyelectriccar.com/forums/showthread.php/mechanical-pwm-46258.html

http://www.diyelectriccar.com/forum...dget-ev-multiple-motors-mechanical-54981.html

http://www.diyelectriccar.com/forums/showthread.php/ghetto-controlleri-51740.html

Etc... and so on.


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## PStechPaul (May 1, 2012)

The flexible band applies pressure to the outside of the brushes, pushing them onto the commutator. It could also be done with hydraulic, pneumatic, or electromechanical plungers.

But the variable dwell cam approach seems to be the most practical. An elliptical cam would be the easiest to make, perhaps, and would give two pulses per revolution. You could use a snap-action switch so the make and break of the contacts would not arc and deteriorate as much.

Of course, as Tesseract says, the stored energy in the motor inductance needs to be handled. So a commutating diode may be necessary. If you add a series inductor, you can essentially make an electromechanical buck converter. This would reduce arcing of the brushes of the series wound motor because the voltage would be a fairly steady low voltage rather than a series of pulses at full battery pack potential.

And perhaps that inductor could have a mechanically variable core which would increase inductance to lower the current. It could even be current-operated so that if the motor current exceeded a certain safe limit it would pull the coil in and limit the current. Or it could directly act on the throttle control to reduce the PWM, giving a mechanical emulation of overcurrent limiting and direct torque control feedback.

I still vote for all-solid state controls using micros and MOSFETs or IGBTs, but it's an intriguing challenge to consider a mechanical alternative.


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## Jamie EV (Oct 3, 2012)

I am going to sketch my idea to make it more clear. It's getting murky in abstract land...


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## Jamie EV (Oct 3, 2012)

Tesseract said:


> So far Qer's viewpoint is the only one that isn't divorced from reality...
> 
> ...because mechanical PWM is dumber than a box of rocks.
> 
> ...



You know what I think is dumber than a box of rocks? People who dismiss others and their ideas out of turn. Just sayin'


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## Jamie EV (Oct 3, 2012)

Tesseract said:


> The second problem that none of you engineering geniuses seemed to have considered is that there is no pathway for freewheeling current during the off time of the mechanical switch. Guess how long the contact surfaces are going to last with you repeatedly interrupting huge amounts of current through an inductor with them?



Actually, I believe that several of us observed that this would be an issue and that we were looking at bleeding off this with capacitors, resistors/diodes or some such mechanism....another option is that since my idea uses a commutator, several of the non motor contacts could lead to a dummy load to disipate charge etc. 

No one here is claiming to be a genius. We're all admitting that it's hair-brained but it's also an interesting thought experiment. THat's what people do when they are dreaming up solutions to interesting problems. They spitball. If you don't get that on THIS of all forums, I don't know what to tell you, buddyh.


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## Jamie EV (Oct 3, 2012)




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## Jamie EV (Oct 3, 2012)

That may have posted larger than I would have liked.


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## PStechPaul (May 1, 2012)

Jamie EV said:


> That may have posted larger than I would have liked.


You can use MS Paint or other image software to reduce size. And you can also use it to make simple block diagrams.

Your idea of changing the speed of a rotating drum doesn't change the duty cycle, but only the frequency.


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## Jamie EV (Oct 3, 2012)

good point. well frequency modulation isn't too bad. It will control speed.


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## Jamie EV (Oct 3, 2012)

http://en.wikipedia.org/wiki/Ward_Leonard_control

check this dude out...


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## Jamie EV (Oct 3, 2012)

actually, you're not quite right about that...it doesn't change the duty cycle...in relation to the frequency...that remains matched to the frequency exactly...however the pulse width does change in relation to the motor itself.

So while you are esentially correct to say that relative to teh frequency of the drum's contact with the brush it is not changing the pulse width....it is in fact changing pulse duration due to rpm variability. 

Does that make any sense?


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## McRat (Jul 10, 2012)

PStechPaul said:


> You can use MS Paint or other image software to reduce size. And you can also use it to make simple block diagrams.
> 
> Your idea of changing the speed of a rotating drum doesn't change the duty cycle, but only the frequency.


Yup, you want the spin speed to give you the appropriate Hz of the PWM, say 1600hz? So if you have 16 triangles on the drum, you need 100 rps, or 6000 rpm, easily done with a small R/C motor. 

So you take a piece of copper rod or thick wall tube about 3" dia by 4" long.

Paint it with resist after careful masking, and acid dip until about .060" metal is removed. Now dip in epoxy or urethane, so there is a buildup everywhere on the outside at least .07" thick. Chuck in lathe, then do a minimum cleanup to expose all the copper that had resist on it.

This is your drum. The first 1/2" is all epoxy, which is the "dead" zone for the brushes. Then starting at 1/2" you start to hit peaks of triangles. As the brushes are moved further down the drum, the % of duty starts to increase. When it gets to where the brushes always touch copper, you are 100%, when you get to where there is nothing but copper, you are 100% and max contact surface area.


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## Jamie EV (Oct 3, 2012)

McRat said:


> Yup, you want the spin speed to give you the appropriate Hz of the PWM, say 1600hz? So if you have 16 triangles on the drum, you need 100 rps, or 6000 rpm, easily done with a small R/C motor.
> 
> So you take a piece of copper rod or thick wall tube about 3" dia by 4" long.
> 
> ...


I stand corrected. McRat had it right all along. That's a good plan....well...as far as bad plans go...


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## Jamie EV (Oct 3, 2012)

I would also use a copper mesh instead of a carbon brush on that in order to avoid wearing out the drum comms too. Copper mesh rests tangentially on the drum and does not require a lot of pressure....it would slide easily up and down the drum too...actualed by the cable....good plan.....I'm gonna go buy some plumping pipe now lol.


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## Jamie EV (Oct 3, 2012)

who sells copper dowels?


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## Jamie EV (Oct 3, 2012)

you also don't need 16 triangles. You need two. like yin and yang. Almost all epoxy on one end...slowly dissipating into almost always copper on the other end. Yup just two triangles means a larger brush for more current. Then spin the drum at appropriate speed and slide the brush and vary the pulse width. fricken genius.


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## Tesseract (Sep 27, 2008)

Jamie EV said:


> you also don't need 16 triangles. You need two. like yin and yang. Almost all epoxy on one end...slowly dissipating into almost always copper on the other end. Yup just two triangles means a larger brush for more current. Then spin the drum at appropriate speed and slide the brush and vary the pulse width. fricken genius.


Someone already beat you to the punch... Please read post #9 for an explanation why this is still a dumb idea. Just sayin'

And BTW - a Ward-Leonard control system comprises a motor driving a separately excited generator at a constant speed. The power output of the generator is proportional to the field current while the commutator and brushes provide a *continuous pathway for load current*.

In other words, no PWM.


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## Jamie EV (Oct 3, 2012)

Tesseract said:


> Someone already beat you to the punch... Please read post #9 for an explanation why this is still a dumb idea. Just sayin'
> 
> And BTW - a Ward-Leonard control system comprises a motor driving a separately excited generator at a constant speed. The power output of the generator is proportional to the field current while the commutator and brushes provide a *continuous pathway for load current*.
> 
> In other words, no PWM.


Read back to me where I said it was a PWM?

Why are you so derisive and abusive?


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## Jamie EV (Oct 3, 2012)

Anything that takes business away from EVnetics I guess...


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## Jamie EV (Oct 3, 2012)

Hmmmm I was thinking about how inefficient the "Rube-Goldberg" Commutator PWM would be....after all, it's going to get hot.....

THen I came across the cooling device that accompanies the Soliton controller on EVnetics. 

Strictly speaking, how hot does that wonderful feat of IGBT engineering get? 

In terms of efficiency, aren't IGBT circuits or Mosfets still turning a lot of battery power to heat? 

I mean, sure there's a motor that spins a vernier comm....and that wastes energy and there's the resistance of the contacts and brushes....and that produces heat....but how does that compare to the circuitry of the rather impressive SOliton? (And I mean no sarcasm, it looks like a great device).

I just wonder if all the electronics don't amount to the same thing wrt wasted energy and heat....just sayin' 
=)


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## McRat (Jul 10, 2012)

I buy small amounts of metal from www.mcmaster.com. And pretty much all my simple hardware. They have a huge catalog and for me, I get same day, or next day service.

2 triangles would be the minimum so it has natural balance, IMO.

Cooling should not be an issue. This is a kamikaze device, not automotive.

It could be made in a weekend for $100 + a buttload of labor.

This kind of gadget is not going to replace a good controller. This is hose clamps and duct tape. However, you'd be surprised how many races were decided by a roll of duct tape.


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## McRat (Jul 10, 2012)

Tesseract said:


> Someone already beat you to the punch... Please read post #9 for an explanation why this is still a dumb idea. Just sayin'
> 
> ....





Tesseract said:


> Ok, since _you_ asked...
> 
> There are all sorts of problems with this idea, but here are the four I see as most damning:
> 
> ...


1) The throttle curve is determined by the shape of the drum contacts. The "triangles" don't have to have straight sides. When I tune a dual purpose diesel, the first 50% of throttle is very gentle in it's ramp-up. Starting a 50%, it ramps up quicker and quicker. This makes it drive like a stock engine on the street, but will still deliver 4 times the factory HP at full throttle.

2) All electric motors start at zero RPM. While the PWM might only be 1%, it's still full voltage, BUT a very short (har-d-har) burst. One brush per triangle, and a lot of triangles should handle it.

3) Can you explain this better please?

4) Materials are always a beach. The reason we can do many things we do today is because improvements in materials. Roller brushes would help. Teflon has the lowest friction, and beryl copper is fairly slippery for a metal.


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## Jamie EV (Oct 3, 2012)

McRat said:


> 1) The throttle curve is determined by the shape of the drum contacts. The "triangles" don't have to have straight sides. When I tune a dual purpose diesel, the first 50% of throttle is very gentle in it's ramp-up. Starting a 50%, it ramps up quicker and quicker. This makes it drive like a stock engine on the street, but will still deliver 4 times the factory HP at full throttle.
> 
> 2) All electric motors start at zero RPM. While the PWM might only be 1%, it's still full voltage, BUT a very short (har-d-har) burst. One brush per triangle, and a lot of triangles should handle it.
> 
> ...



yup teflon (or polytetrafluoroethylene) would be a prime candidate for it's frictionless qualities....mind you if it catches on fire, the gasses are poisonous...so there's that to consider...not that I expect it to. 

They make Cadillac engines with a Teflon coating that is so good, they say the engine doesn't need oil. 

For brushes, why not use a piece of copper half-pipe? Or quarter pipe...it could be polished up so that it doesn't snag of course and it will rest on the roller with very light springs...you could replace it for next to nothing....would pass enough current easily...would shuttle up and doen the roller quite well.

You could mount fan blades on the roller to vent hot gasses.

the hardest part would be milling the roller...and that's not really that tough.


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## Qer (May 7, 2008)

Jamie EV said:


> Anything that takes business away from EVnetics I guess...


No, both I and T has tried to be helpful and explain as good as we can why this is a road to disaster, like we tend to do in this forum. We have also tried to help people with problems even if they've bought the "wrong" controller simply because we do have a lot of experience and don't mind to take the time to share it. Well, at least usually we don't mind it.

However, since your attitude stinks I'll stop trying to explain why your contraption will fail (which it will, no matter what you do) and let you learn the hard way since I guess that's the only way you'll learn.

Btw, your post has been reported as abusive.


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## dladd (Jun 1, 2011)

I can assure you, Evnetics is not at all worried about losing business to you.


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## McRat (Jul 10, 2012)

I would think there is a place for both "correct" EV systems, and "ghetto" EV systems.

I can buy a $6000 brand new aluminum engine that puts out a conservative 405HP and gets 28mpg in a 3200lb car, with SLEV (low emissions) rating.

How much HP will $6000 buy you with excellent EV parts?

From what I'm seeing, doing a motorcycle with 100HP is in that price range.

If you want more home built EV's, I wouldn't dismiss ElCheapo plans or attempts, I'd embrace them. I have a $35,000 engine in my pickup, but I don't tear into guys who try and come up with cheaper solutions, even if I know their shortcut isn't going work well. Why? Because I started out building custom motorcycles and VW Bugs ghetto parts. Everyone needs to start somewhere.


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## Jamie EV (Oct 3, 2012)

dladd said:


> I can assure you, Evnetics is not at all worried about losing business to you.


THat's good


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## Jamie EV (Oct 3, 2012)

okay so just to be clear here. I get no kick out of battles of words with internet warriors. 

I don't misrepresent myself. I'm a long time follower of EV builds and certainly not a whiz at electronics or electrical engineering...nor do I pretend to be. If I throw an idea out there, it's no skin off my nose if you shoot it down.

THe rotating PWM idea is at the outset, a bad idea. Not because it won't work....because there's really no reason why it should not. Is it strictly a PWM...well maybe not...semantics...not interested in them.

Now, here's the thing....the thread was Kamikaze. Full power, balls to the wall....the person that suggested a mechanical pwm was just throwing it out there...I ran with it. Perhaps foolishly however it is an interesting thought experiment....you know...the kind of fun stuff that resulted in the theory of relativity?

Thought experiments are just that. If we were to be able to mill the parts, hook it up, spin the PWM....run a small motor on it....fine....would I want to hook up a brand new 9" motor and a 96v lithium pack to it? Probably not.


That said, there is a right way and a wrong way to give constructive criticism....belittling people because they are saying something you "know to be dumb" nomatter how dumb, or HOW MANY TIMES you heard the dumb idea, is still wrong. Now I realize that it's really hard to behave like good little boys and girls on the consequence free internet, but please try.

I may be a noob, and dumb, and have bad ideas, and my mother may even dress me funny....BUT....you're still not entitled to make character judgments based on that...lest they be made about you as well.


Homemade EV controllers (IN ANY FORM) are likely to blow up in your face. IT's the nature of the voltage and current. We KNOW that. Stop stating the obvious ad nauseum please.


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## Tesseract (Sep 27, 2008)

McRat said:


> I would think there is a place for both "correct" EV systems, and "ghetto" EV systems.


Not if the "ghetto" system is likely to cause property damage, fire, injury, death, etc...

I really don't care when people try to make their own electronic controller. Sure, it's just as likely to blow up as a mechanical one, but the key difference is that most people naturally assume (usually correctly) that a homebrewed electronic controller is going to be dodgy!

In stark contrast, people invariably assume that a mechanical PWM controller will be bulletproof because it doesn't have any wimpy silicon bits inside it to blow up, conveniently forgetting that, for example, even the big contactors used in EVs need to be pressurized with special gases and use strong magnets to blow out any arcs that might form upon opening. 

Also, few seem to recognize that directly controlling duty cycle is itself a bad idea, whether you use an electronic or mechanical switch, but that is a second order problem you only have to worry about if you haven't blown up your motor or battery pack the first time you crank it up to 11.



McRat said:


> How much HP will $6000 buy you with excellent EV parts?


It's not possible to do an apples-to-apples comparison because you need to replace an ICE with a motor, controller, battery pack and charger to make a vehicle electric, but the battery pack dictates your range as well as your power (unless you are controller or motor limited, that is).

It is possible to build a drag-racing pack with Hawker lead-acid cells for relatively little money but which won't have enough capacity take you more than a couple miles per charge, if that. Or you could spend a little more and make a drag racing pack with LiPoly cells which will deliver a bit more power and maybe give you 10 miles of range.

Where the ICE vs. Electric comparison really gets interesting is well above the "crate engine" performance and price range. How much would it cost you to buy a 1000hp ICE for one of your trucks? My guess is the price of an EV drivetrain wouldn't seem so expensive at that power level.


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## Siwastaja (Aug 1, 2012)

Jamie EV said:


> In terms of efficiency, aren't IGBT circuits or Mosfets still turning a lot of battery power to heat?


Typically 1-4% depending on design. Not much in the terms of efficiency, but still enough to need liquid cooling in _high power _designs. 2% loss at 100 kW is 2 kW, enough to make a few cups of coffee quickly. But still, it's only 2%...  We are talking about high power levels here.

IGBT's have somewhat constant voltage drop (about 2V), whereas MOSFETs have resistance-like drop. High-voltage MOSFETS, on the other hand, get quickly more expensive and their resistance rises. This is why IGBTs are good at higher voltages, MOSFETs at lower.

There are two types of losses, conduction and switching. If you diy, you should IMO minimize the switching frequency (within limits, for example, 1 kHz) to minimize switching losses. The minus is audible noise.

And diying an electric controller is really not black magic. Instead of problems, I like to list solutions whenever they are at hand, hence my earlier post with a few points. Let's not forget this should be a DIY site. But yes, learning comes from mistakes and if you just need a working controller, you will save time and possibly money by buying one. But if you want to learn..... do your science! As you can see here very well, it would be more rewarding to actually do with your hands and even fail, than listen to grumpy dismissing by those who have experience. OTOH, not everyone with experience is grumpy, but how fun is it to hang around at internet forums? _Too much_ time spent in this kind of environment just makes people sick, and this is a universal observation, not only specific to this forum. Build a lot, report it, and discuss the results. It should work better. Google around and read books, and of course ask questions, but don't expect supporting words; just pick any factual points you were given between the lines, be happy with those, and go on.

As a personal sidenote, the reason we are building our own (AC) controller (fine so far with no blown IGBTs...) and rewinding our own motor, is the price. We will have about $7000-8000 at our disposal and it will be mostly used for batteries. Everything else - build from scratch. Yes it takes time and probably it would be easier to work and get paid for that time to buy commercial products, but we like electronics so it's a hobby - and the DIY spirit.


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## Jamie EV (Oct 3, 2012)

If you're doing what White Zombie's Plasmaboy did, drag racing the wuarter mile a few runs and then resting, you could probably get away with Hawkers (he used them) andgot great results. His lead acid time is only slightly slower than his Lithium time! LIke in the hundredths of seconds.

YHou could probably also do the ghetto device. I can guarantee that hwn he floors his Zilla 2K, the motor endures stress....the controller endures stress....the contactors cook etc etc. 

I think it's safe to say you would not put this crazy thing in a daily driver! 

BTW, if you look up Electrovette, their controller wasn't much better than the Mechanical PWM.


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## McRat (Jul 10, 2012)

Tesseract said:


> Not if the "ghetto" system is likely to cause property damage, fire, injury, death, etc...
> 
> I really don't care when people try to make their own electronic controller. Sure, it's just as likely to blow up as a mechanical one, but the key difference is that most people naturally assume (usually correctly) that a homebrewed electronic controller is going to be dodgy!
> 
> ...


I can do a Kamikaze 1000HP for about $6000. Nitrous and a big spinning thingy. It won't last, but it will do it.

I've done a whole bunch of "unsafe" stuff over the last 35 years. Nobody is going to live forever. There are $200,000++ Bonneville entries that are deathtraps, and kill the motors after a just a few passes.

For dragracing, once you do your burnout, then stage, it's WOT. You don't need sophisticated throttle control unless you're indexed or bracket racing. On a manual trans Z06, at first I didn't even lift to shift, stab the clutch, and bang the gear. Then I started hosing the syncros. 

You are most likely to be killed while driving on the street, and it's head injuries, broken necks, and fire that kills mostly. How many of you wear a helmet, firesuit, and HANS device?

Think about this, a Powerglide is a freakin' antique. It is primitive, simple, and needs rebuilding often. It's perhaps the most common drag-only trans. Why? It's cheap compared to your other options.

I'm certainly not an "anti-tech/computer" guy. I run digital engine controls, cylinder pressure sensors, programmable traction control, and datalogging. And I do my own engine programming.

Think about this: does your EV have electric brakes? Electric doors? Magnetic bearings? Electric steering? No. The money is best used for other items. Every project as a budget.


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## Jamie EV (Oct 3, 2012)

Wow, it seems that this line of discussion has deep division and I'd say that it's not going to be resolved here. And here I went thinking that I was the cause of a lot of argument...clearly not. There are some arguments that are just dying to erupt on here.

DIY versus sophisticated commercial unit....well clearly it comes down to cost/benefit.

If someone wants to get into drag-racing, they want to save every last ounce of energy, want to spend extra money on batteries, transmissions etc. then kamikaze power switching might be viable...on the caveat that it's for racing. 

The thing about race parts is that they are designed to be light and break down relatively easily. Race cars are rebuilt after every race...dragsters are rebuilt after a few runs. 

It's the difference between a street rod or a drag racer....one car you tow to the event...the other you drive around town in. Now if you want to drive to your event, race and drive home, that's different....you might be inclined to drive there with a simple low amp controller, pop in your doomsday machine after polishing the contacts, changing out the batts and prepping the car....then blast off when the Christmas tree tells you to.

Your controller will need heavy service after that, but so what? You were going to do it anyways. 

I think if someone wants to bomb around on the road with a Zilla 2k, that's their prerogative but most people have neither the money nor the inclination to do that....and I have it on good authority that ghetto setup DO in fact show up at the drag strip.


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