Paul & Sabrina's cheap DIY 144v motor controller

[Christ]

Oh - it gets better - I had to work in a locked down building for 8-16 hours a day for part of the time I worked there, and signed a federal NDA stating that I would never divulge any of the sensitive information I might have obtained from working in said area.

Smoke breaks consisted of a shower, escort to the break room (giant ionizer humming overhead) and a security agent watching over you while you did everything. Fun Fun.

Keep in mind, this used to be IBM. In fact, it's IBM's original plant, and most of their equipment.

That etch machine was new.. it's an EIT patented build, contract-built by 8 companies that each one only knew about the part they built. In fact, one of the executives that was in charge of hiring contractors to build parts of the machines accidentally hired the same company working under two diff names... he was fired, and so was the contracting company... the parts they were contracted to build/manufacture were scrapped, and the design of the machine/object changed accordingly.

EIT's biggest money maker right now is aerospace/medical, but they're picking up in the defense/military offense industries at a pace faster than you or I can blink.

Anyway - the etch chamber alone (not the developer or the rinse/cleaning agent/scrub/rinse/clean/rinse/dryer) wouldn't fit in your bedroom - let alone your bathtub. LOL.

It's only 4 feet wide, but it's 20 feet long, not including the etch-specific rinse chambers.

[MPaulHolmes]

The microcontroller is still good! However, the voltage regulators I'm using are now no good. I had 11 extra of the 7805, and zero extra of the 7812's, and Radio Shack isn't answering their phone, so I'm guessing they are closed.

The 7805 takes up to 20v input, and has 5v output. The 7812 takes up to 27v or something input, and outputs 12v. Both are unfortunately below the 36v that I inputted to them.

Dang it.

[bennelson]

My original 36V charger for my motorcycle was the same size and shape as a nice little 12v trickle charger I had.

I confused the two once. 12V chargers do NOT like 36 volts running through them.

I still miss that charger...

[MPaulHolmes]

Thanks, Ben. I'm becoming more and more careful now. It's good I'm getting all my "do careless stuff" routine out of my system, cause when the big boys get here (200v mosfets), great care must be taken!

Fortunately, the voltage regulators are about $0.35 each.

The design from the printer ink is still wet on the copper, so I think I"ll take it to the garage and hit it with a heat blower, since there's nothing else of value I can do out there until tomorrow. (anger flames coming out of my ears. If I had a futuristic cougar right now, I'd punch it right in the head, and make it growl like Ben's car)

[MPaulHolmes]

OK, so the micro-controller was bad, the 7812 and 7805 voltage regulators, the mosfet gate driver, and that's it!

It works again! Never again will I hook 36v up to a 7812 or 7805 voltage regulator. I changed the code so it's very smooth. It is going to feel extremely smooth when accelerating. I also changed the thermal shutdown so that it moves into a high pedal lockout, so that you have to let go of the throttle before you can accelerate again once it has gone into thermal shutdown mode. I took out the gentle rampup, because the current is under control in other ways now. I'm getting lots of help from a head design engineer of brushless motor controllers in some country in Eastern Europe. I forgot where. His name's Fran. He's on the EV Tech list.

My wife and brother said they bought me a surprise tool of some sort that will help with the project. I can't wait to find out what they got! They don't have much money, so I don't think it will be too fancy, but I'm still really excited. Christmas is over! What's the deal? No surprises allowed anymore!

-Paul

[bennelson]

Originally Posted by MPaulHolmes

...they bought me a surprise tool of some sort...

Plasma Cutter!

[Tango Charlie]

Nose hair trimmer!

[MPaulHolmes]

I added a mosfet to the controller. Now it can handle about 40 or 50 amps continuous I think. I'm going to hook it up to the car to test out the current limiting on a much larger motor (lower inductance and lower internal resistance, so harder to current limit). A whopping 6.7" diameter. Wow! hehe. They are 100v mosfets, so the 72v in the car shouldn't be a problem.

My 2 new oscilloscope probes came a couple days ago, so I can watch 2 mosfets at the same time (2 channels at once!). They need to turn on and off at almost exactly the same time, or else you get major problems. For example, at a 400 amp current limit, if 8 mosfets are supposed to be sharing the load, but one turns on faster than the others, then it's conducting all 400 amps for an instant! That's bad.

Fortunately, the 2 seemed to be perfectly in sync. I also put them in as far apart as possible, so they were a sort of worst case.

I experimented with etching 4 ounce copper with my baby drill press. It works really well, but it's sort of hard to do a straight line. It feels like sewing. First, you have the height of the drill just below the copper level. You push the PCB forward, following a line, stop the drill press, turn the PCB, turn on the drill press, push it again, following the line. It's fun!

I made a home-made hang glider a long time ago, and it brought me back to when I was sewing the cloth part.

[Intrigued]

Originally Posted by MPaulHolmes

...baby drill press.

Was that your surprise tool??? Or are we still painfully waiting?

[MPaulHolmes]

Intrigued! Thanks for accepting my friendship request! I still don't know what it is yet. It makes me real mad, too. I think it's in the mail. My brother told me to wait, and that he wouldn't give me any hints.