Paul & Sabrina's cheap DIY 144v motor controller

[bennelson]

Paul, your understanding of "High Pedal Disable" sounds about right. Basically just a safety feature to keep your car from taking off when you turn it on if the potentiometer is misadjusted or malfunctions.

My understanding of a 2 vs 3 wire throttle is that most potentiometers have three connections on them. Using the center pin and one outside pin gives you a resistance signal of oh, say, 0-5KΩ. If you use the center pin and the OTHER pin, you get 5-0KΩ.

When I bought the twisty-throttle for my motorcycle, it had three wires in its cable. I had to call the dealer and ask which too wires to use. Knowing what I do now, I could just measure the wires with a multimeter and figure out which two to use.

[MPaulHolmes]

Since this is a budget controller, maybe it could be assumed that people are using budget throttles too? Ben's throttle was 3 wire! That's encouraging. I think the first version will require all 3 wires (since it's super easy that way to send 0 to 5v to the analog to digital converter on the micro-controller), and when the Thailand people get around to sending that stupid LM317, I'll change it to a 2 wire pot, since even cheap pots can just use 2 of the wires, like Ben was talking about. Thanks Ben!

I'm doing the wiring for a first test run. I'm not done yet. My son is sick and I have to get ready for class on monday! Dang it!

[Christ]

Paul - I went back and read the post about adding the pedal ramp to the software... I understand better now why you did it, but I still maintain that 5 seconds might not be necessary :P We already had that discussion though.

AFA the "high pedal disable" setup - I've seen (read, seen, whatever) where people have used dual pots for this type of thing... one pot is the control, the other is a reference.. if they're too far apart, the controller will cut the signal.

So if your control is at 50%, and your reference is at 46%, you go at 50% throttle.

If your control is at 70% and your reference is at 50% - you lose throttle control, and in many cases, this can be used to engage the "generator" function as well, to stop the vehicle.

It's more of an insurance policy against a pot going bad than anything, but seems like it could be a nice safety feature to program as an option. (Not necessary, but easy to utilize.)

[MPaulHolmes]

We tested the controller with the power section! You can hear the faint 4 kHz tone on the video. It's actually really quiet in real life. It is almost completely masked by the sound of the wheel spinning. It worked on the first try! I was scared! I'm so happy! I don't think it will be that terribly difficult to replace the 100v mosfets with 200v mosfets, and to use 10 of them instead of 5, and to use bigger bus bars. The 200v version can put out 50 amps per mosfet, so 10 would make a 500amp controller. The software is already done for the car's version. The main problem is the 200v mosfets are like $15 each, so it will be a while before I get a bunch of them.

Here's the video!!!

[bennelson]

Originally Posted by MPaulHolmes

The main problem is the 200v mosfets are like $15 each, so it will be a while before I get a bunch of them.

Perhaps you could hold a fund-raiser or a virtual bake sale?

You would have to enable cookies in your browser.

[MPaulHolmes]

Very funny Ben!

[Intrigued]

Have you done some sort of flux capacitor (pre-charge resistor ) for your controller? By the time you get to the big voltages - and the big bucks investment - you'll sure want to protect the thing!!!

[MPaulHolmes]

Absolutely, Intrigued! Good Eye! For the 12v test in the video we used a 1.3kOhm, 1/8th of a watt resistor. hehe, sort of puny. I think we will go to Radio Shack today and get a few beefcake 10w resistors and put them in parallel, so we can do a higher voltage test. But I have to do stuff for my job! AAAHH, Anger! Anger Flames! Why can't people just get money for not working? That would be awesome.

[Funny]

That would be Communism Paul...

[MPaulHolmes]

Oh Snap(ping turtle), you're right. Plan B: Everyone else work, and I lay back and take it easy!

We got 4 50 Ohm 10watt resistors from radio shack. I'm going to wire them in parallel to get a single 12.5 Ohm 40watt precharge resistor. I'll take the oscilloscope to the garage to see the shape of the PWM signal through the mosfets from drain to source? I have never thought about how to do it, or maybe from gate to source? Or gate to drain? hehe, how about all of them to see what happens. Hopefully the voltage spikes on the transitions from the mosfets being off to being on aren't too big. They need to stay below the 100v max.

I don't think I'll hyper-analyze and optimize the bike version too much, because the car's version will be pretty different as far as how the power board is laid out. I think for the car version, we'll definitely do maybe 1 mosfet at a time to make sure everything is working right, since those 200v monsters are expensive!