Car starter on PWM

[AndreiRS]

Hi all. Oooof I have been away for a while. Not really doing much on electronics or HV, just renovating the house and working a bit. I also had to put my TC on the shelf because capacitors are not available here for a decent price. Then I got back to building a diy jet engine lol. But I did a project on electronics and today I remembered I should share it.

So I got a normal PWM circuit, like the one you would get on ebay, it uses a LM324 as signal generator. 555 generators used to burn mosfets for some reason. Then I just removed the IRF540 from PWM board and put a mosfet push-pull driver there. Just a NPN and PNP transistors in series.



But instead of 1 mosfet, I used 4 IRF3205 in parallel, which should be capable of 110A each. And I think one 10ohm resistor on each gate. Yeah they will probably explode a lot earlier before those 110 amps hahah. But they are doing good till now. I started using 3600Hz as calculated using some "motor constant", it didn't work well. Latter I lowered it to 500Hz to have more torque available.

I'm kinda quiet here on the forum, I just don't have anything good to post and I don't know a thing about SSTCs. I will read other people post, maybe I can help someone a bit.

The plan is to use this on a electric bike. I just don't like "torqueless" brushless DC motors. Brushed motors from car engine starters are way more crazy haha. I had to remove all the front part of the car starter. Then I bought another rear end cover from the same model and used it as front cover too. Video is in portuguese but I said there about the same I said here. The 2.5mm² wires got warm with this small test. But it was just a test. I will use 10mm² wires.

[T3sl4co1l]

No catch diodes across the motor?

Tim

[AndreiRS]

I have a MUR1620 in parallel, but it is at the connector part.

[petespaco]

I didn't think that car starters were rated for continuous duty.  is this one different?

[AndreiRS]

It is just like all others. But I will "drop" it inside a small radiator fluid tank. I have seen some people do that, it works. Then the sprocket will come out from the top.