Paul & Sabrina's cheap DIY 144v motor controller

[MetroMPG]

Originally Posted by MPaulHolmes

I also got some sheet metal and wrist strap to make a static free workbench in the garage.

Sorry, that admission has just disqualified you from the "duct tape, cardboard and hammers" school of DIY ecomodding.

[MPaulHolmes]

Originally Posted by TheSGC

What are you using for current limiting?

For the bike, I'm using no current limiting. In my case, the motor's resistance and GHETTO old lead acid batteries will be enough current limiting to keep the mosfets from blowing up. I've already tried the bike with a simple on/off switch at 60v (no controller. it was awesome torque,horrible range, very jerky and scary).

For the car, I'm going to use an off the shelf hall effect sensor. It's like $16 I think. It can read up to 600 amps.
Possible Choice for Hall Effect Current Sensor

That sounds like an awesome project you are doing! I hope you keep me updated. I like the idea of having modules that can attach to increase the max amps. That sounds very interesting!

[MPaulHolmes]

Originally Posted by MetroMPG

Sorry, that admission has just disqualified you from the "duct tape, cardboard and hammers" school of DIY ecomodding.

You are right. It felt really wrong... But, I don't know if this makes things ok, but I will use some used christmas wrapping paper to make the surface less cunductive. In case I ever drop a battery upside down on the table or something! Actually, that would probably still be really bad since the paper isn't very strong.

The table is grounded through a 1 megaOhm resistor to the ground pin of an outlet.

[MPaulHolmes]

Today was pretty productive. First, it snowed a whole bunch! It doesn't snow that much around here, so it's been really cool. It's late now, and the sky is bright pink. Weird!

The EVTech list has been really, really helpful. For the car's version of the controller, 4 ounce copper pcb is required. That stuff is sort of hard to come by at your local radio shack. What it means is that every square foot of the pcb (printed circuit board) has 4 ounces of pure copper on it. That's a lot! Someone on the EVTech list is sending my wife and me 2 pcb's of 5 OUNCE copper for free!!! That's thick!

The bike version of the controller will be able to handle around 40 amps. So, there has to be a copper bus on which all the current flows. Each mosfet will contribute about 8 - 10 amps to the bus. Such a high current requires pretty heavy copper. I'm thinking of using 10 gauge wire for the bus.

So, here's the rub. How do you solder a lead (leed) from a mosfet to such a heavy wire that will be about 6 or 7 inches long? Try it! Take a soldering iron and try it! It's tough. The dang wire won't heat up enough. So, 2 days and many EVTech.org conversations and reading and trying several things that don't work led to an awesome solution! But that's for another update... I just heard the doorbell ring...

HOLD EVERYTHING!!! WHO COULD BE VISITING IN THIS SNOW STORM? ONLY THE UPS MAN!!!!!!!!! That's right! The programmer and 2 microcontrollers (atmega8) just arrived! heck ya dude! This is where things get interesting...

Oh no! It's a static sensitive device? I need a static free workstation! Hmm... What to do? hahaha!

[Intrigued]

Originally Posted by MPaulHolmes

So, there has to be a copper bus on which all the current flows. Each mosfet will contribute about 8 - 10 amps to the bus. Such a high current requires pretty heavy copper. I'm thinking of using 10 gauge wire for the bus.

So, here's the rub. How do you solder a lead (leed) from a mosfet to such a heavy wire that will be about 6 or 7 inches long? Try it! Take a soldering iron and try it! It's tough.

For cryin' out loud, man! Find a piece of scrap copper tubing somewhere, pound it flat with your Oprah hammer, drill a few holes in it, and BOLT the wires you solder to the leads to the now flat copper strip...or something like that...

...or am I missing something here...

[MPaulHolmes]

You're not missing anything! Want to know something funny? Lee Hart, the Godfather of Electric vehicles on the EVDL and the EV Tech list suggested something close to what you just said. You know what, I think your idea is maybe better than what I was going to do. There are a few things to deal with, like the bolt heads hitting the pcb underneath the copper bars, but that's not so bad. It can be worked around I think!

Edit: Well, maybe I'll save that way for the car, because I don't need that much copper for the bike version. hmm...

Sometimes you get going in one direction, and you need someone to come along and throw in a little common sense! Thanks, Intrigued!

[Intrigued]

You're welcome!

Although I'm not so sure about the common sense part... I just took 4 times to log in, because I had my stupid "Caps Lock" on...

[MPaulHolmes]

programmed the micro-controller (after some difficulty getting everything plugged in right! ANGER!) with a program that lets you see some LED's so I could actually tell that it worked. It worked! Unfortunately, the program needed to run a motor controller doesn't really make it easy to see that it's working. I need a dang throttle, and a bunch of electrical components, and just build the left half of the motor controller itself (most of the low power side in the schematic above) just to test the stupid program!

So, I programmed the ATMEGA8 with the motor controller program, on faith, trusting that it's all good. Now I need to build a prototype of the low power half of the controller. No mosfets on this version. Basically, I'm going to be "driving" an LED (baby motor! hehe). Now, this LED will get brighter and dimmer through PWM. I guess I'm making 3 motor controllers, a WEENIE BABY LED 5v 0.01amp "motor controller", a medium 72v 40amp bike controller, and a monstrous 144v 400amp (500? 600???) car motor controller! Hold me back, hold me back!

I have to go to Sylvan really soon, and it's super stormy and snowy! Man, I wish I had more time!

The pictures show the STK500 with the ATMega8 micro-controller plugged in (ready to receive it's motor control program), and various screen shots, including showing that it has been successfully programmed! Hurray!


"Time is the fire in which we burn!" (some guy on like Star Trek 8 or something, when Captain Kirk got stuck in the Nexus with Whoopi Goldberg and Captain Picard)

[Intrigued]

ooooooOOOOOOoooohhh! (Like that bunch of alien toys on Toy Story)

I see a possible sideline for MPaul Enterprises, here... not only building controllers, but tweaking the programming on all of your buddies' computers in their cars, so that they get even better gas mileage!!!

<You have saved us from the evil Fuel Lord. We are forever in your debt!> (us)
(you)

[Daox]

Great work Paul!!! Looking forward to more updates.