# Series DC controller w/o Transistors



## remy_martian (Feb 4, 2019)

All kinds of tricks were played to control locomotives, light rail, and forklifts.

Inverters are pushing 99% efficiency these days, so why on earth would you use, ick, a rheostat?


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## Inframan (Jan 30, 2011)

The rheostat would not directly control the motor the "commutator" would. This would be an entirely mechanically controller electric vehicle essentially making it emp proof.


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## Inframan (Jan 30, 2011)

The small motor spins the commutator and the large motor is controlled by how fast the small motor spins. Although we may need something to prevent jack rabbit starts something for smoothe acceleration.


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## remy_martian (Feb 4, 2019)

Yes, I understand about the rheostat. Still very crude.

What you've conjured up is a speed control. EV's run on torque control.


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## Inframan (Jan 30, 2011)

Well being crude is kind of the idea here and what difference does it make how I achieve PWM as long as it is refined enough to control on vs. off time sufficiently enough? If an emp of solar flare does happen I could be the only one with an electric bug out vehicle.


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## OR-Carl (Oct 6, 2018)

An electric bug-out vehicle? Really? If every charger is fried, your range will be limited to a single charge. Most conversions are lucky to get more than 100 miles. 

As for your idea, it sounds like you are already convinced, so I say build it and let us know how it went.

If that doesnt come together, a bicycle is about as EMP proof as you are ever going to get. Just duct-tape your AR-15 to the handlebars, and get out of the city early to avoid all the zombies that you probably imagine all the "radiation" is going to produce.


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## remy_martian (Feb 4, 2019)

If you have to "bug out", maybe you're living in the wrong place?

Most EVs' gonads are inside a Faraday cage, fwiw.


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## Inframan (Jan 30, 2011)

How about some actual technical ideas about the controller itself not just political sarcasm for "preppers". Its makes me wonder if anyone here on this site actually has any knowledge of electronics or engineering.


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## remy_martian (Feb 4, 2019)

There are engineers here with more in their pinky than you'll ever know. Insulting them isn't motivational or inviting.

What controller? It's a "rheostat".

If you're talking about your doomsday device, you were invited to go build it. Ideas are a dime a dozen...the engineering details, materials, and a working prototype is where the meat & potatoes are. You either need to do those yourself, or hire someone who has no conscience in taking your money.

While it's a hare-brained, nutjob, basement inventor kind of project, go for it. Go for it because you are not impeded by knowledge, both in subject matter and in need for such a contraption. A simple spark gap or arrestor tube will protect an IGBT...if there was a need...it's in a Faraday cage, so there isn't one.

Don't forget to build a battery charger using your same PWM gizzy, and feed it with a monster wind turbine generator (guessing it needs to be in the half-megawatt+ range to survive your doomsday currents) for power cuz that apocalyptic pulse is definitely going to fry your solar cells (they're solid state diodes with fine, antenna-like wires...not to mention pointed right at the sun).

EV electronics are buried in a 2 shell, minimum, set of Faraday cages. We'll be driving past you in the opposite direction to your bug out as you have your hood up at roadside changing melted commutators every five miles.

But it'll probably get you an honorary appointment to the Anachronism Society if it works. Do it. Be the first to extinguish an arc plasma in air quickly (brushes arc), which is the first problem you'll encounter in mechanical narrow pulse generation in air. It could get you a PhD....seriously.


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## Inframan (Jan 30, 2011)

This site has to have had an extreme downtick in users and with people as bitter and shitty as you are I can see why.


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## remy_martian (Feb 4, 2019)

People enjoy the candid perspective, and the free engineering, so anyone worthwhile is not bolting for the door.

It's the snowflakes and those looking for yes-men that are intolerant of my style and run off crying and tugging at the admin's apron.

But, on behalf of everyone, thanks for the useful content and for sharing all your research here.

By the way, this isn't a one on one help line. It's a capture of info useful to thousands in future.


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## cricketo (Oct 4, 2018)

Neither the solar flares or a weaponized source of EMP can fry the power electronic components like MOSFETs and IGBTs, it's the digital control electronics that is a lot more sensitive to that kind of stuff. It is possible to build strictly electronic (analog) oscillation circuits that will be immune to any practical sources of EMP thus eliminating the need for any mechanical circus. For the additional inspiration one can also look at the design of the 1970's SCR-based motor controls.


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## brian_ (Feb 7, 2017)

While the whole idea makes no practical sense, it is an interesting question. It could be thought of as "if I were in the 1920's and wanted a better controller to help electric cars succeed against gasoline competition, despite transistors not being invented yet, what could I build?"



Inframan said:


> Does anyone here know if an attempt was ever made to make a DC controller that operated without the need for a rapid switch like a transistor? For instance you could have a rheostat power a small dc motor at variable speed and on the shaft of the motor you would have a commutator that would break the connection between battery positive and motor positive..


You're replacing a reliable electronic switch with a mechanical switch... but you still have rapid switching.



Inframan said:


> For instance you could have a rheostat power a small dc motor at variable speed and on the shaft of the motor you would have a commutator that would break the connection between battery positive and motor positive and spinning this small motors commutated shaft rapidly would cause a pwm like effect.


But it wouldn't. PWM means that the width of the pulses is modulated, not the frequency; a rheostat controlling the motor which rotates the commutator would only change the frequency. 

To get PWM with a commutator, you could use two commutators on a common shaft, with a phase difference between them controlled by a mechanism like those used for timing control on camshafts in modern engines. With large dead spaces between active commutator segments, pulse width would be determined by the overlap between the segments of the two commutator sections. It would presumably work as a DC motor controller (although with only 0 to 50% duty cycle), with sufficient filtering.

Another approach would be to change the commutator rotational speed to change pulse frequency, but create constant-width pulses, effectively changing the duty cycle and producing a PWM-like effect. A pulse-on relay could produce the constant-width pulses, but without transistors that would presumably depend on some sort of resonant circuit.

Once you accept components such as capacitors and inductors, you can omit the whole rotating mechanism and just build a resonant circuit as if you were driving a transistor, but drive a relay instead. Unfortunately, any relay will not last long in this service.


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## cricketo (Oct 4, 2018)

brian_ said:


> But it wouldn't. PWM means that the width of the pulses is modulated, not the frequency; a rheostat controlling the motor which rotates the commutator would only change the frequency.


Wouldn't the width and frequency be directly related ? The slower is the rotation, the longer a particular commutator contact is engaged increasing the pulse width while reducing the frequency.


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## brian_ (Feb 7, 2017)

cricketo said:


> Wouldn't the width and frequency be directly related ? The slower is the rotation, the longer a particular commutator contact is engaged increasing the pulse width while reducing the frequency.


Pulse width, yes, but PWM is really about duty cycle. For instance, If you produce a chain of pulses of 1 millisecond long, with a pulse starting every 5 milliseconds, the duty cycle is 20%. If you cut the frequency in half and produce a chain of pulses of 2 milliseconds long, with a pulse starting every 10 milliseconds, the pulse width is doubled but the duty cycle is still 20%, which will typically be interpreted as having the same meaning. I agree that if the pulses are made by brushes contacting a commutator segment, changing the shaft speed will change the frequency and pulse width together; that means that the duty cycle will be unchanged... and that's the "throttling" factor in a switched power supply.


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## piotrsko (Dec 9, 2007)

Late to the conversation, but 10 years ago over in the motor section there was a single speed spinning switch that had tapered cones which would function as a PWM style switch with obvious limitations. Couple people built them, but results were generally unsatisfactory. I don't know why someone would use such a device other than curiosity or stubbornness but YMMV. If your looking for high voltage high current regulation, perhaps go look at large airport runway lighting systems using saturation effects in toroid coils


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## Deane (Mar 21, 2020)

Inframan said:


> Does anyone here know if an attempt was ever made to make a DC controller that operated without the need for a rapid switch like a transistor? For instance you could have a rheostat power a small dc motor at variable speed and on the shaft of the motor you would have a commutator that would break the connection between battery positive and motor positive and spinning this small motors commutated shaft rapidly would cause a pwm like effect.


Inframan, EE here. The reason no one does this is that your mechanical switch would need to be on and off at least 50 times a second to give smooth power to the motor. That would mean that every hour your car runs it would be switching 180,000 times! You can imagine you would be replacing the switch every week. That is why electronic switching is used. It does not have a wear-out limit to how many times it can switch.


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## tripper1000 (Mar 10, 2020)

Hi, I work in avionics on some very old aircraft electrical equipment. What the OP suggests is similar to how they did things on aircraft in the 40's and 50's (rotary inverters, commutators driven by variable or constant speed DC motors, carbon piles, and generally mechanical analogue solutions to what we digitally now days etc). The problem with this kind of electro-mechanical technology, is that it wears out quickly and it introduces a lot of other failure points. In addition it also adds weight, complexity and cost. In terms of nuclear hardening, a lot of electronics in the military is nuclear hardened - stuff like clamping devices in circuits to shunt away EMP's - it is like anti-static hardening on steroids. 

I've worked on mega-expensive crappy aircraft electro-mechanical 3 phase inverters from the 1960's that are very failure prone, and that could easily be replaced by a PICaxe and 3 FETS that would never fail again ever (but don't due to certification complexes) and thought how digital technology has made the world a better/cheaper/more reliable place.


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## tripper1000 (Mar 10, 2020)

piotrsko said:


> If your looking for high voltage high current regulation, perhaps go look at large airport runway lighting systems using saturation effects in toroid coils


Also used in ancient aircraft - called a magnetic amplifier.


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## Frank (Dec 6, 2008)

Early EV's used contactors to switch batteries in and out of the circuit at varying (and discrete) voltage jumps. For example, a 48V system would start at 12V, jump to 24, 36 and finally 48 volts or maybe 12,24,48. IIRC at 12V all 4 batteries (assuming use of 12V batteries) would be in parallel, at 24V there would be two pairs of two and at 48V, all batteries in series. At least that's the way I remember it: I could be wrong but I'll bet there's a circuit drawing kicking around showing how it all came together.


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## piotrsko (Dec 9, 2007)

Deane said:


> Inframan, EE here. You can imagine you would be replacing the switch every week. That is why electronic switching is used. It does not have a wear-out limit to how many times it can switch.


Not so much, as I am doing effectively this with my series DC motor and have 22,000 miles, ~10 years on the brushes which are appropriately sized and shaped for the task. I would get more life if I didn't live in a silicone dust enhanced desert, but that's a side issue.

There were numerous issues with a mechanical controller but brush life wasn't necessarily a part of that. Arc suppression, noise and suprising bearing failure were, as was sizing the conductors and cooling. A somewhat sucessful unit was bigger and more complex than the motor it controlled


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## Inframan (Jan 30, 2011)

So in regards to the scr controller do those generally have a microcontroller of some sort to switch the power side on and off. Can anyone direct me toward a basic circuit diagram of one for our application?


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## remy_martian (Feb 4, 2019)

An SCR triggers on a tiny current into its gate... one of the worst choices for high RF fields, imo.

Stick with your mechanical solution, because once you go silicon, you'll arrive at the best choice for RFI being what's used today in production


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## Inframan (Jan 30, 2011)

I have actually built although somewhat crude motor controllers in the past with hockey puck transistors and an arduino but just to be clear you are in disagreement about SCR as a choice with others here who have suggested it? If so don't thump your chest at me shouldnt your beef be with them?


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## remy_martian (Feb 4, 2019)

My postings are informational for everyone who comes along. I rarely do one on one support - it's a waste of my time. If I answer or suggest in a topic, it's for the benefit of the thousands that come along over ensuing decades. Otherwise, I'd take it to PM and consult, which again is not worth my time.

Debates and rebuttals to what I post or provoke are open season and welcome...that's how I add to my own knowledge as well.

Others suggested the simplicity of bygone times as far as SCRs go - yes, the passives are EMS immune... the trigger electrode is far from it.. 

Nobody suggested it as a solution to the RF nasties during Putin lobbing one at the bugout crowd 💀


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## cricketo (Oct 4, 2018)

Inframan said:


> So in regards to the scr controller do those generally have a microcontroller of some sort to switch the power side on and off. Can anyone direct me toward a basic circuit diagram of one for our application?


Take a look at this doc: http://www.bigjoesupport.com/parts/SUPP/44.pdf
It's part of GE EV1 system, and has full (or nearly full) schematics of the power system and a decent overview of the SCR functionality. You may be able to find other docs for things like forklifts that describe variants of that thing with additional details.

I suggested it because they're doing switching at a low frequency. Low frequency tells me that one could utilize non-digital, non-IC components to implement it. The EV1 control cards do have a handful of ICs in them, but they're not strictly necessary. That card's main purpose is oscillation.

One, you can find most of those components already assembled into a working unit - either on Ebay, or pull it out of an old forklift. Two, my hunch was that building a low frequency driver without ICs would be easier than a high frequency driver, and ICs would be the most vulnerable component when it comes to the EMP. But @remy_martian knows electronics better than I do, so for instance if he says SCRs are vulnerable to EMP, then perhaps they're not a good choice for your academic project.


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## Inframan (Jan 30, 2011)

cricketo said:


> Take a look at this doc: http://www.bigjoesupport.com/parts/SUPP/44.pdf
> It's part of GE EV1 system, and has full (or nearly full) schematics of the power system and a decent overview of the SCR functionality. You may be able to find other docs for things like forklifts that describe variants of that thing with additional details.
> 
> I suggested it because they're doing switching at a low frequency. Low frequency tells me that one could utilize non-digital, non-IC components to implement it. The EV1 control cards do have a handful of ICs in them, but they're not strictly necessary. That card's main purpose is oscillation.
> ...


I would ask some more questions like if a "controller" could be designed using a clutch system instead of a commutator but if I do I might risk even more ire on these forums then I already have.


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## kennybobby (Aug 10, 2012)

Don't worry about the detractors and critics, press on with questions in order to expand your knowledge and satisfy your curiousity--that is how progress is made. i don't know what is a clutch system, so i'm curious about what it would be if you can describe it.


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## brian_ (Feb 7, 2017)

Inframan said:


> I would ask some more questions like if a "controller" could be designed using a clutch system instead of a commutator but if I do I might risk even more ire on these forums then I already have.


A commutator and a clutch do completely different things. Perhaps if you describe your proposal using terms that you understand (apparently not "commutator"), we might be able to provide constructive comments.


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## OR-Carl (Oct 6, 2018)

Will Cars Still Run After an EMP? The Surprising Truth | SuperPrepper.com


If an EMP attack occurs, will your car come rolling to a stop, never to work again? Here's the truth about whether modern vehicles can survive an EMP.




www.superprepper.com





Sounds like in the very unlikely event that an EMP happens, you can probably just drive your Camry full of canned pork and beans to your "bug out location." 

If you are still not convinved, and want to make absolutely sure that your precious cargo of beans makes it to your mountain stronghold, maybe just wrap your bug-out-mobile in tinfoil. Drill a hole in the garage floor, drive in a grounding rod, wrap that baby up and ground her. Burrow inside and see if you get a cellphone signal with it all sealed up. Zero bars means your beans are ready to roll!


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## cricketo (Oct 4, 2018)

OR-Carl said:


> If you are still not convinved, and want to make absolutely sure that your precious cargo of beans makes it to your mountain stronghold, maybe just wrap your bug-out-mobile in tinfoil. Drill a hole in the garage floor, drive in a grounding rod, wrap that baby up and ground her. Burrow inside and see if you get a cellphone signal with it all sealed up. Zero bars means your beans are ready to roll!


Note that if the cellphone has no signal it just means it's blocking the specific frequencies used by the carrier, other frequencies may still get through. It's kind of like if you put your phone into the microwave (without switching it on of course), it will lose 2.4Ghz wifi but both cellular signal and 5Ghz wifi will continue to work.


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## Inframan (Jan 30, 2011)

Mechanical PWM


I've found evidence that people talked about using mechanical instead of electronic PWM for controlling electric motors in the past, but I'm not finding much information. Why wouldn't mechanical PWM work great, and be very inexpensive? "It consisted of a cylinder, rotated by a small electric...




www.diyelectriccar.com




Apparently this has already been discussed on here scrolling through for info now.


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## remy_martian (Feb 4, 2019)

One of my profs was telling us a story about how the Americans were dissecting a MiG after its pilot defected with it and were laughing hysterically at how crude the electronics were - it was all based on miniaturized vacuum tubes. Then someone pointed out that vacuum tubes are EMP robust...

I still say you can make a nice PWM circuit using triodes and use six TV transmitter tubes to drive the stators.


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## Inframan (Jan 30, 2011)

Well lay the basic circuit on me Ill try it out


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## remy_martian (Feb 4, 2019)

The PWM circuit using vacuum tubes is embedded in the schematic here:






Audio Synthesis via Vacuum Tubes


Descriptions of the various modules in a home built music synthesizer.



synthpanel.com





They talk about the source but don't cite it 🤬

All dangerous high voltage stuff, so if you smell bacon...it's you getting fried 😂


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## cricketo (Oct 4, 2018)

remy_martian said:


> The PWM circuit using vacuum tubes is embedded in the schematic here:
> 
> 
> 
> ...


How are the vacuum tubes rated in respect to currents ? Would it be possible to say pump 500A ?


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## remy_martian (Feb 4, 2019)

Transmitter tubes are water cooled...


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