I need a controller to control the speed of an automobile engine starter. I want to put this motor on a winch and be able to very the speed at which the winch can pull. Any ideas or schematics or sites that I can go?
Thanks

 

A starter motor is a VERY poor choice, they are designed for one specific purpose only, and aren't a very good general purpose motor.

But speed control on that size of motor is very complicated, and very expensive, there are various commercial ones available, as used in Robot Wars etc. (but not usually using starter motors).

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Nigel is right that in general a starter motor is a poor choice. It depends on what you want to use the winch for. For some applications it is doable but not simple.

People are using them for launching sail planes and similar. I think the key here is a rather short duty cycle, sort of like starting a car, or a lighter load to keep them from overheating. Starter motors are designed to run at full speed. Running it slower may result in rapid over heating. Depending on what you are using the setup for you may want to mount a temperature sensor to the starter.

Brushed DC Motor control is most often done by Pulse Width Modulation. Generating the PWM signal can be done with or without a micro controller. Then you have to find some transistor like device that can switch off and on fast enough to carry the load needed to drive the starter motor. I am sure others can give you a suggestion on that.

If the winch only needs to run in one direction you can do the circuit with a single transistor. If you need to reverse it you can use an H-Bridge with 4 transistors or a single transistor and a DPDT reversing switch.

Term like PWM and H-Bridge can be found on wikipedia.

HTH

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We need more information from the OP. What type of starter motor does s/he intend to use? The newer models of automotive starters typically use a small, high-speed motor with gear reduction. Th older models with which I am most familiar are more robust and are what is most often used to launch sailplanes and the like.

I have experience with the Ford longshaft starter in a controllable-speed sailplane winch and am willing to share that circuit, if it is what the OP intends. We used it for a few years in the club and never once, except for testing, used the contollable speed aspect to launch. A side benefit of the controllable speed was an electronic brake, which was used. John

 

You are right. When it comes to cars I live in the past. I refuse to own one that I can not repair... Good nite..

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Hey guys,
Thanks very much for all the replies. I told my buddy to just use his winch as it is and he said ok.

Thanks

 

That's not true, just use a normal speed contoller (specialised IC, 555 timer, two comparators etc.) , MOSFET driver and huge MOSFET.

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Maybe the real question is what is very complicated?

The system I designed and built is 2 KW or more at 12 volts. You need a "free-wheeling" capacitor and a good sized diode or a half-H bridge. I went the half-H bridge route, which then means the MOSFET driver needs to be a bit more sophisticated with gate feedback, etc. for timing. At those power levels, you don't want any chance of the top and bottom gates being on at the same time. Also, the starting current can be enormous, so it helps to have a little soft-start.

It is simple in concept, but gets more complex as you eliminate bugs to get something that works. I ended up with two ICs (a specialized motor control and a half-H driver with feedback control) and 10 mosfets (2 sets of 5 in parallel). And, it works well enough to pull the wings off a composite glider. John

 

I've never heard of a free-wheeling capacitor.

I've heard of a free-wheeling diode or an RC snuber though.

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Sorry, sloopy word use. I meant the capacitor that is usually placed across the top and bottom rails in the half-H configuration. 4QD calls it the Main capacitor http://www.4qd.co.uk/fea/half.html

John

 

OK, another question. Gyrocopters, a small flying machine uses a free spinning rotor, 23 feet long and about 50 lbs to fly. These rotors are pre-rotatated to about 175 to 200 rpms with a small 12 DC motor. Just what type I dont know. The pilot hand starts the rotor then intermittingly presses a button to the dc motor. This is a slow process and puts stress on the rotor mask from the torque of the motor. My question is, couldnt a dc motor controller work better? It would offer soft start and you could use a pot or Micro to steadly bring it up to desired rpms. Is such a controller available or a schematic to build one.

Thanks

 

It might be that a DC motor controller that can handle the current required is more expensive than just a button/switch/relay.

It's probably just cost. A contact costs a lot less than a a bunch of transistors, capacitors, ICs, and PCBs.

 

Actually, I think it would be an interesting concept --similar to pulsing a pendulum at the right point. I would start with sensing blade position and speed. Then have a MCU give the right number of pulses. I suspect one limitation is the weight of the battery to give sufficient power, and assume the version to which you refer still keeps a short take-off roll to get the rotor truly up to flying speed. John