Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

Hi Jack! I was just noticing that I have 11 pins unused, so that would be no problem at all. You might want to email Toyota with that idea.

[sawickm]

Originally Posted by MPaulHolmes

Right now, I'm just converting PCB Artist to DesignSpark libraries. I'm up to 14 custom components now.

Paul,

What do you think about DesignSpark ???

I downloaded and installed it yesterday. For the price, you can’t beat it !!!

I want to try to port some Eagle stuff I have into it.

- Mark

[MPaulHolmes]

I love DesignSpark. It's IDENTICAL to PCB Artist, so there was ZERO learning curve. I've got most of the custom components recreated in it now, and I've been copying the schematic to it.

[Kasmodean]

Hello everyone,

First before I start I want to say awesome job to everyone involved with open revolt, especially you Paul.

I was trying to learn how to make a small dc motor controller for a robot I am building and came across the idea of PWM. I then figured after I made my robot to work, I could use the same principle to make a controller for my car. ( I have previously looked at doing a electric car conversion but controller cost has held me back.) The problem was it was one thing to make a robot controller with no safety features and making the same type for my car. It is then that I came across this forum. I have read up to page 150/370+, and I am still reading but I have a few questions on something that everyone seems to take for granted that are probably really simple, but I don't understand.

1) Every controller circuit I have looked at either has a capacitor connected to the motor's + & - terminals, or no capacitor, or capacitors around the + & - terminals and from + terminal to ground. In your schematic you have lots of capacitors from Batt + /Motor + to ground. How does that control the voltage spikes hitting the diodes from the motor - terminal while the mosfets are off? Or if that is not the purpose of them, what it?

2) Everything I have heard about diodes say they shouldn't be placed in parallel, especially if no equalizing resistor is attached. But your circuit has a bunch of diodes in parallel. How do they equalize and not have the best performer take more current then it can handle? This is also important because I was thinking of using IGBTs instead of mosfets and those aren't suppose to be in parallel either but everyone is saying you can do it.

EDIT: I just found on the diodes spec sheet that the forward voltage drop inceases as current increases. It is because of this that they balance, right?

[adamj12b]

Originally Posted by Kasmodean

Hello everyone,

First before I start I want to say awesome job to everyone involved with open revolt, especially you Paul.

I was trying to learn how to make a small dc motor controller for a robot I am building and came across the idea of PWM. I then figured after I made my robot to work, I could use the same principle to make a controller for my car. ( I have previously looked at doing a electric car conversion but controller cost has held me back.) The problem was it was one thing to make a robot controller with no safety features and making the same type for my car. It is then that I came across this forum. I have read up to page 150/370+, and I am still reading but I have a few questions on something that everyone seems to take for granted that are probably really simple, but I don't understand.

1) Every controller circuit I have looked at either has a capacitor connected to the motor's + & - terminals, or no capacitor, or capacitors around the + & - terminals and from + terminal to ground. In your schematic you have lots of capacitors from Batt + /Motor + to ground. How does that control the voltage spikes hitting the diodes from the motor - terminal while the mosfets are off? Or if that is not the purpose of them, what it?

2) Everything I have heard about diodes say they shouldn't be placed in parallel, especially if no equalizing resistor is attached. But your circuit has a bunch of diodes in parallel. How do they equalize and not have the best performer take more current then it can handle? This is also important because I was thinking of using IGBTs instead of mosfets and those aren't suppose to be in parallel either but everyone is saying you can do it.

Kasmodean,

First, Where in MA are you located?

Second,

You can parallel diodes, you just have to watch for thermal sharing. You want them all to be the same temp all the time. Same thing with the IGBT's. It is very important for those that they do not get warmer then others or they will conduct more and you will end up with thermal runaway.

-Adam

[harlequin2]

I have my controller up and running and I've read lots of this thread to try and see what settings other people might have used or experimented with, but haven't had much success. Does anyone know where I might find this info? Or maybe all those who have built one of these things could put the parameters up here somewhere, together with battery specs and motor type plus a few comments on the performance?
BTW, a big thank you to the developers of RTD Explorer!

[Kasmodean]

How about the capacitors? I would figure the capacitor would be connected to the M- bar to filter out motor's inductance voltage ripple, but they are on the B+ bar, what is their purpose? Are they just providing an average stable voltage to the motor? If so the voltage on the B+ bar has to go all the way back to the battery and then to the motor. Wouldn't it be better to have the B+ bar also be the M+ bar on the other side on the controller to get the maximum effect of the caps?

Also, if the diodes are to smooth voltage to the motor, what is filtering voltage spikes coming out of the motor and hitting the diodes?

Please don't take my questioning offensively, I am just curious and trying to understand the design better.

Adam,

I am located in Fall River, MA. Thank you for the information about the diodes, so as long as i have them all equally heatsunk they should be fine.

[apowers]

The B+ bar and the M+ bar are the same bar.
alvin

[jyanof]

Originally Posted by harlequin2

I have my controller up and running and I've read lots of this thread to try and see what settings other people might have used or experimented with, but haven't had much success. Does anyone know where I might find this info? Or maybe all those who have built one of these things could put the parameters up here somewhere, together with battery specs and motor type plus a few comments on the performance?
BTW, a big thank you to the developers of RTD Explorer!

A while ago we started a controller settings page on the wiki. There's a few entries in there.

Open ReVolt/Controllersetting - EcoModder

[MPaulHolmes]

You want to keep the inductance as small as possible, so the capacitors, mosfets and diodes need to be really close. If you had no caps, the pulses would have to come from the batteries, which would be far away, and the ESR would be high. The large inductance would cause very large voltage spikes as the current tried to change quickly, which would probably destroy the mosfets. The diodes are just there to take the current that's flowing through the motor windings when the mosfets are off. They don't really smooth anything out. If the diodes weren't there, the current would piledrive right though the mosfets from drain to source, since current can't stop instantly. It's like a water pipe with current racing through it, and all of the sudden, you close a valve. The pipe will probably explode since the water will still want to keep going. The diodes give an alternative path for the water to go.

EDIT: I feel like most of what I said above makes sense to me, but let's see. a sudden near short circuit (closing the mosfets) makes an almost short circuit. Tons of current wants to suddenly flow. With capacitors charged, it can mostly come from them, which is a very short distance to the mosfets.

What causes the oscillations in voltage seen by the mosfets from large distances? Something about LR or LC or LRC or who knows what. Could someone explain that?