# dirt cheap crude controller?



## Qer (May 7, 2008)

It should work well for testing, but you will deplete the lowest battery in the string way before the rest of the batteries so the wear will be very uneven and I would advice that you charge the batteries individually to be able to compensate for the differentiated charge levels. Also make sure you never completely discharge the lowest battery! The current from the rest of them will probably ruin it in no time.

Of course, the range will suffer from this approach (you won't use the top battery much for example), but, as I said, it'll work well for testing.


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## vmike (Jun 27, 2008)

My simple controller for my first conversion back around 77/78 was similar to the switch in the drag electric car article. I used a camshaft made from poker chips rotated by the accelerator pedal. Each pokerchip was fitted with a roller arm microswitch that actuated a surplus high current aircraft relay. I had six cam/microswitch/relay combinations to step the battery voltage to the motor. I drove the system for quite awhile before building an SCR controller. The batteries didn't go dead any slower after the conversion to SCR. But then again, back then I didn't know what a new battery looked like.

mike


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## Vwbeamer (Jun 16, 2008)

You can make a contactor controlller. Say you have a 72 volt system. the pack is wired into two 36 volt packs.

The contactors are wired so the "low speed" is 2x 36 volt packs in Parallel.
High speed is 2 x36 volt packs in series, for 72 volts.

This gives you a high and low speed on the motor. And equal discharge on all batteries.

With a 5 speed manual tranny, this gives you ten speeds.

There was actually a EV company selling a kit with a controller like this, can't find a link.

I did find this-

http://www.aaroncake.net/Circuits/cntctcon.asp


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## TX_Dj (Jul 25, 2008)

I like that idea better than switching more batteries into the mix in a sequential fashion like 12v, 24v, 36v, etc. 

In the "good old days" there were even setups that basically used a big rheostat to control the motor's speed, but the disadvantage of that is that when you're going slow, you're still using as much power as going fast, just the extra power is dissipated as heat.

A solid-state controller is a better choice because it provides a more "smooth" power curve, with nearly infinite levels of power to meet your immediate requirements, and is less "jerky" than switching from one power level to another.

Unfortunately right now it's very hard to find used equipment for cheap due to the demand. Several years ago, it was easy to find a cheap used controller as the new controllers like the Zilla were coming to market, because our power-hungry brethren like John Wayland and others were going for the big amp controllers for their NEDRA rigs, and thus a lot of "lesser" controllers were available as surplus. Don't let that spoil your hopes though... if you put out enough queries in enough places, you may find someone with a surplus 1221C or similar collecting dust on their shelf.


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## gerd1022 (Jun 9, 2008)

Just build a PWM controller using the MC33033 chip and a surplus IGBT...

i built mine for about 60 bucks, and it has similiar specs to a curtis, with the possibility of adding an IGBT module to increase the power...

i can post a scematic if you want...


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## hertfordnc (Jul 30, 2008)

THanks for all the good info. 

> i can post a scematic if you want...

That would be great. 

I was also wondering if it would work to use a cheaper controller on a 36volt bank for low speed control to get you out of the driveway and then add the rest (in series) after the controller? 

thanks


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## TelnetManta (Jun 5, 2008)

I need a controller to control a treadmill motor running at 144V to run my AC. At full power its spinning way to fast. Any ideas?


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## gerd1022 (Jun 9, 2008)

Here is a schematic..

Controller.JPG


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## hertfordnc (Jul 30, 2008)

thanks.

But what am i missing? if you can do that for $60 why are off the shelf controllers so expensive? Why isn't someone making that for $200 ? 

dave


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## gerd1022 (Jun 9, 2008)

thats a good question... especially in bulk, the components would probably be right around 100 new...

i heard somewhere that the zilla is actually only about $300 in components, but they are selling them for 2K.

granted there is some engineering and construction to pay for, but it does seem a bit ridiculous...

thats why i made my own!


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## TelnetManta (Jun 5, 2008)

I wish I understood that drawing better. Could you build one of these for someone? If so what would the cost be?

As I mentioned, sorry to tag onto your thread dave, I need to control a treadmill motor for A/C.

Ben


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## gerd1022 (Jun 9, 2008)

TelnetManta said:


> I wish I understood that drawing better. Could you build one of these for someone? If so what would the cost be?
> 
> As I mentioned, sorry to tag onto your thread dave, I need to control a treadmill motor for A/C.
> 
> Ben


PM Sent...


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## madderscience (Jun 28, 2008)

If you are willing to put up with a fairly low performance car (50mph or so top speed) you can look at 72v controllers (watch ebay) and probably find a used alltrax or curtis 72v, 400A controller for a couple hundred. Don't know if that meets your definition of dirt cheap or not but the cheapest 120v and up ones are over $1k. Favor the alltrax if you go that route.


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## hertfordnc (Jul 30, 2008)

no, the dirt cheap option is just for development and testing. Once I know the car, the motor and the batteries are all up to the task, then I would be happy to spend real money on a proper controller. 

d


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## TheSGC (Nov 15, 2007)

gerd1022 said:


> thats a good question... especially in bulk, the components would probably be right around 100 new...
> 
> i heard somewhere that the zilla is actually only about $300 in components, but they are selling them for 2K.
> 
> ...


The reason why you pay so much isn't because of the components, but the software running them. It has to be completely bug free and able to handle redicuous amounts of variables and know what to do if one of those variables FUBARs itself. I am in the process of building a sweet programmable controller, using a PIC as the basis. It has about $75 in parts, but I have probably put over 40 hours in perfecting the code, and I haven't even added the sweet features yet. And there are bugs I am finding everytime I test it. I pretty much have a PIC, voltage regulator, op-amp (for current sensing),IGBT driver and status LEDs. Took about 2 minutes to build hardware circuit, but programming it has been the real adventure.


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## morvolts (Jun 19, 2008)

gerd1022 said:


> Here is a schematic..
> 
> http://www.diyelectriccar.com/forums/attachment.php?attachmentid=485&stc=1&d=1217440692What is the consumption of the trigger circuit?


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## morvolts (Jun 19, 2008)

Has anyone built one of these using the schematics Gerd1022 provided?
I have several questions about this and am in the middle of rounding up components to build one.


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## gerd1022 (Jun 9, 2008)

hey sorry i didnt get back to you...

im having a little trouble with the design i posted, i keep toasting drivers... but im working on it, ive got a design for the power stage laid out...

actually to elaborate, when morvolts asked about the power consumption, i went out to my prototype to measure the amps that the power supply running the drive circuitry was putting out, and somehow my driver pretty much exploded into flames (maybe im exaggerating, but it was glowing enough to scare the crap outta me) and it melted the saddle i had it in... The power supply was only putting out .5 A at the time as well...

I'm a ME not an EE, but it seems that if the driver can output 14A peak, it should have some heak sinking capabilities?

I do know, however, that the PWM side works perfectly. I even borrowed my friends oscilliscope, and it is outputting a pretty clean square wave from 0-100% with a small turn of the 10K pot.

Any advice about the drive circuit would be great.

ps on the layout: the upper IGBT is going to be held in an off state to simply be used as a freewheeling diode for the circuit. This is for two reasons, I know the specs match the transistor, and i couldnt find any fast enough diodes for the price of another IGBT. Also, the green box is a Tamura 600A current sensor.

Power Side.JPG


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## ga2500ev (Apr 20, 2008)

It has some serious limitations:

1. THE IGBT has a 2-3V drop. At 200A you're burning 400-600W of power in heat. Which also means you have to cool the IGBT.

2. There are no safety features like current limiting.

3. It has limited programmability.

4. It doesn't include any commercial development costs. If it were $200 and each and every one got sent back burned up, that would be too useful.

With some appropriate safety features it would do well for a DIY. I'm interested in the high power section and plan to replace the low power section with a microcontroller.

It'll be good enough to get things moving.

ga2500ev


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## gerd1022 (Jun 9, 2008)

yeah i agree... its good for a tinkerer, but as a commercial product, it would need more more refining...

i know that zilla uses IGBT's, how do they get around the large voltage drop? or do they not and is that why they are water cooled?


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## morvolts (Jun 19, 2008)

This was one of the reasons I asked what the power consumption was on the IGBT trigger circuit.
I saw that the amp was rated at 14A but think that is for extremely brief periods and not continuous duty.
If .5A is killing it then something else must be wrong.
Keep us informed Im ready to build!


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## gerd1022 (Jun 9, 2008)

yeah the wierd thing is tho, i was running it for about a week with no problems, the driver wasnt even heating up (it was cool to the touch)

so something might have been shorted... the only thing i changed was that i put the multimeter in to measure amps...

im going to take a look at it after work today.


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## TelnetManta (Jun 5, 2008)

It's a real bummer because I had planned to use one of these small controllers simply to power a treadmill motor off of pack voltage. Now I don't know what to do but am watching with much interest.


Ben


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## TribesMan (Aug 6, 2008)

What about the voltage spikes in your system? Switching high currents usually produces a lot of spikes. That is usualy more lethal than heat...


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## morvolts (Jun 19, 2008)

gerd1022 said:


> yeah the wierd thing is tho, i was running it for about a week with no problems, the driver wasnt even heating up (it was cool to the touch)
> 
> so something might have been shorted... the only thing i changed was that i put the multimeter in to measure amps...
> 
> im going to take a look at it after work today.



Sorry I may have jinxed it by asking.
Voltage drop across it could calculate the amperage


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## gerd1022 (Jun 9, 2008)

haha thats ok, if you can jinx it that easily, imagine how much jinxing could be done by other drivers on the road...

about the voltage spikes, i was only running the motor at 12V, although i was running my 8" forklift motor... however, none of this should affect the driver right? its my understanding that it take the same amount of gate charge at 12V as it does at 144V to run the IGBT...


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## morvolts (Jun 19, 2008)

I would think that the output switching would be totally isolated from the control circuit so Yes I agree that 12vdc shouldnt matter vs 144VDC.


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## gerd1022 (Jun 9, 2008)

ok heres something i found... the gate capacitance of the PRX CM600 igbt is 120 nF, and the driver is rated for a load capacitance of 15 nF nominal, and the graphs in the datasheet (http://pdf1.alldatasheet.com/datasheet-pdf/view/87433/IXYS/IXDD414PI.html) dont even go up past 100 nF. 

Maybe a higher power mosfet intermediate step is in order.


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## TelnetManta (Jun 5, 2008)

YEAH! Figure that thing out so I can get one, Gordon!!!


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## gerd1022 (Jun 9, 2008)

THis document has all the answers.

i think, i havent finished reading it yet.

http://www.pwrx.com/pwrx/app/Driving-IGBT-Modules.pdf


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## gerd1022 (Jun 9, 2008)

ok so im looking into getting a BG1A development kit that is made specifically for the PRX module. the data sheet for the kit is here: http://www.galco.com/techdoc/prx/bg1a_dat.pdf

it should be about 50 bucks plus another 10 or so in components. its got all the bells an whistles, and it should interface nicely with the MC33033. Next to work on a current limiting circuit using the Tamura sensor i have.


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## morvolts (Jun 19, 2008)

gerd1022 said:


> THis document has all the answers.
> 
> i think, i havent finished reading it yet.
> 
> http://www.pwrx.com/pwrx/app/Driving-IGBT-Modules.pdf



Interesting reading
perhaps they have some generic "spec" applications that will work.


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## lazzer408 (May 18, 2008)

gerd1022 said:


> http://www.galco.com/techdoc/prx/bg1a_dat.pdf


Good greif... 20a peak gate drive current!? For a single igbt!? No wonder igbts are dropping like flies on diy controllers.

I'm glad I went mosfet.


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## TribesMan (Aug 6, 2008)

20A drive current is WAY too much for one IGBT.
I design small AC and BLPM controllers, but I use only MOSFETs, because we are working with battery voltages up to 72V and up to 15kW power.
In our designs we use up to 8 parallel MOSFETs and 3A drivers, but even in that setup we have to limit the driver current with series gate resistors to slow things down. High di/dt or dv/dt transitions are hard to work with, because you get a lot of voltage spikes as a result of stray inductance. And voltage spikes are bad, belive me 
On IGBTs there is even a possibility of latchup at high di/dt or dv/dt transitions.


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## TheSGC (Nov 15, 2007)

Just curious if this design has made any progress. The first thing I notice is that the gate drive is only 12 volts, and the IGBT really needs 14-15 volts to function properly, and to limit ringing. (That's probably what's been toasting the drivers.)


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## gerd1022 (Jun 9, 2008)

hey guys....

sorry ive been busy with school and stuff, but the car and controller have been coming along. i just soldered up my custom driver circuit using the vla500, testing will be done on friday with one of my friends three oscilliscopes (all free from the dump!) If all goes well, i could have the controller in the car by this weekend.

Also on friday i am going to machine the aluminum water cooling plate for the cooling system that i have. Does anyone have any idea how to calculate the maximum heat off of the IGBT? in the datasheet it says 4100W but i can't imagine that it would generate that much heat for very long... (41 lightbulbs??) I think i am going to include a decent sized water resevoir in my cooling loop so that it can act as a buffer for acceleration heat buildup.


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