DIY Solid-state automotive (altenator) voltage regulator
LoopyByteloose
Posts: 12,537
Quite some time ago, Parallax built a wonderful robot that used a small gasoline engine to directly drive a small alternator.
http://forums.parallax.com/forums/default.aspx?f=21&m=151769
Everything was controlled by an SX28, including the output of the throttle which in turn controlled the altenator. The electrical power was used to drive hefty DC motors and to charge a small gel cell. But it seems that the project was abandoned and my guess is that the risk of over-charging the gel cell was just too much for Parallax to continue with the project.
Take a look here for another option.
http://www.amsterdamhouseboats.nl/voltage_regulator.htm
Personally, I thought this 'hybird' design scheme was quite exciting and offered a lot of choices for robotics projects, especially robots that bring a lot of electrical power into remote locations (for lighting? for tool use?).
I also think Nuts and Volts recently had an altenator regulator design a few issues ago, but I've not yet located.
I'd love to see this project revisited.
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Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Post Edited (Loopy Byteloose) : 7/24/2010 12:03:26 PM GMT
http://forums.parallax.com/forums/default.aspx?f=21&m=151769
Everything was controlled by an SX28, including the output of the throttle which in turn controlled the altenator. The electrical power was used to drive hefty DC motors and to charge a small gel cell. But it seems that the project was abandoned and my guess is that the risk of over-charging the gel cell was just too much for Parallax to continue with the project.
Take a look here for another option.
http://www.amsterdamhouseboats.nl/voltage_regulator.htm
Personally, I thought this 'hybird' design scheme was quite exciting and offered a lot of choices for robotics projects, especially robots that bring a lot of electrical power into remote locations (for lighting? for tool use?).
I also think Nuts and Volts recently had an altenator regulator design a few issues ago, but I've not yet located.
I'd love to see this project revisited.
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Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Post Edited (Loopy Byteloose) : 7/24/2010 12:03:26 PM GMT
Comments
That's almost as outrageous as a steampunk robot would be
It sounds smelly, flammable and quite dangerous.
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justasm.blogspot.com/
Actually, if the hybrid approach also enabled the wheel motors to create battery charging, it really becomes exciting.
Here is the Nuts & Voltage version of a regulator:
http://nutsvolts.texterity.com/nutsvolts/201006/?folio=20#pg22
It certainly seems to be more rugged as it doesn't use an op amp. Everything appears to anticipate spikes up to 100 volts or so.
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Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Post Edited (Loopy Byteloose) : 7/24/2010 12:02:08 PM GMT
I couldn't agree more - I'd really like to revisit that particular project.
You wouldn't believe the interest that it generated. The YouTube
The project really needs to be opened up again, for both improved mechanical and electrical regulators. I think there's great power potential for this kind of application. In fact, right now I could use the exact system - I'm building a robotic cataraft (about 6' long, 5' wide) to study GPS navigation. It weighs about 100 lbs and will use the new Crustcrawler thrusters. I've thought about solar but I can't carry enough of our DIY solar panels to generate 15A @ 12V.
I'll see if we can't get this project restarted. The forum crowd could really help me out with an improved design, I'm sure.
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Ken Gracey
Parallax Inc.
Follow me at http://twitter.com/ParallaxKen for some insider news.
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"Let's not bicker and argue about who killed who."
Both rely on tailor-made control of field coil is the alternator. The automotive regulators are not suitable for such - they expect more horsepower. And, the fact that thermistors provide such a key role in simple, cheap safety is equally important. Alternators can run so hot as to melt the copper. And who wants to watch a gel cell bulge or a conventional automotive battery boil and bubble acid?
Initially I thought I could never DIY an automotive regulator as it was a vibrating relay or something. That's no longer true, high amperage darlington transistors look quite easy and better. It is not a complicated circuit.
And every time I look at a gel cel battery charging circuit, I keep wondering why there isn't a thermal feedback system involved. I strongly suspect the battery manufacturers exploit overcharging to shorten the life of their product (like speed exhibition sells more tires). So if one can put a thermistor on the battery and have the regulator use that information intelligently, you have another big win.
I suspect in many cases, a micro-controler, like the BasicStamp might extend a battery's life by years through additional sophisticated thermal management. But of course, even the simpler analog approach within the DIY automotive voltage regulator of reducing charge rate as heat increases makes the whole system far more rugged and much safer.
A huge side benefit is that one may actually preserve fuel that is wasted in excessive charge.
The other interesting aspect that I've recently discovered is that apparently automotive spikes are lower voltage that AC mains spikes.
For years I imagined both being thousands of volts and hard to control, but now I am seeing a lot of remarks that 100VDC is about the peak for automotive spikes (maybe more amps though). I feared designing circuits for automotive would just burn up my cherished components, so I avoided automotive applications.
But that new info means these spikes are manageable by using devices that will tolerate up to 100VDC; such as 100 VDC rated darlingtons and inserting MOVs in the 30 volt range for protecting your typical 78xx voltage regulator (or better yet, the LM2940-xx series which are optimized for automotive problems). I imagine there is a whole interesting design project in just knocking down these automotive spikes (back to coils and capacitor filter design).
Why use alternators? They are everywhere second hand.
And one either has to produce DC to charge batteries or produce exact RPM for AC to get 50/60 cycles per second. It is easier to not have to exactly control the RPMs of the engine. Also if you want to put AC into the grid, it has to be in sync with the grids AC cycle as well. So it is much easier to revert to charging lead acid storage cells.
Fortunately more and more things we use can work off the grid - LED lights, cordless electric drills, computers, telephones, ...
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Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
By using a solid-state analog approach, all those kinds of nasty noise disappear. And I see a flyback diode on the field coil is also suggested, which further removes spikes.
In sum, this alternative may be a much cleaner electrical environment than a normal automotive charging system.
On another front, I went shopping for 30VDC MOVs today (to protect the 78xx regulator from automotive spikes). Not on the shelf locally.
I am looking at another devices, a 30 volt 'poly-fuse', but is is much slower to respond, causes a complete shut down of the supply voltage, and there is a wait for recovery. It would seem the 'poly-fuse' might offer a safety cut of for the alternator's field coil if too many amps are passed through, but it won't do anything to protect delicate micro-controllers. I have to located some 20-30 volt MOVs
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Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Post Edited (Loopy Byteloose) : 8/2/2010 2:45:54 PM GMT