Paul & Sabrina's cheap DIY 144v motor controller

[edown]

Thanks Paul, And I'm driving all 7 fet's with one 10 ohm 1/4 watt gate resistor.. I plan to put one resistor per fet in the next one.. PS: I just took it up to 130 amps, and still going!

[MPaulHolmes]

1/4 watt is fine. There was a long discussion about that on the EV Tech list. 130 amps! yahoo!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Somebody hold this guy back! He's out of control! hahah!!!!!!

Wait! Is it 130 battery amps or motor amps? If it's battery amps, then its even more motor amps!

[edown]

I’ve been thinking about multiple gate drivers, and it seems that if one fails, you wouldn’t know until you let the smoke out of the remaining fet’s . So I was wondering if you could take each driver output to an input of an AND gate (like a DM7415) and signal a shut down? As long as the drivers are in sink the AND gate will stay high..

[NiHaoMike]

Use a discrete gate driver if integrated ones cannot handle enough current. All the MOSFETs must be driven with the same signal to ensure load sharing.

[MPaulHolmes]

Originally Posted by edown

I’ve been thinking about multiple gate drivers, and it seems that if one fails, you wouldn’t know until you let the smoke out of the remaining fet’s . So I was wondering if you could take each driver output to an input of an AND gate (like a DM7415) and signal a shut down? As long as the drivers are in sink the AND gate will stay high..

Let's see. If the driver fails, (and this is personal experience talking! haha!) make darn sure you have a path from the driver output to ground through a (OOOOHH LET'S SAY...) 1 kOhm resistor. That will keep those fets off, and prevent the fet gates from floating and settling at around 4 volts, which is bad. hehe. In that scenario, you would lose half of your current carrying capacity, which could cause major problems if you are pulling a lot of amps, because the good driver would still be running his (or her!) mosfets really hard, because they would now also be doing all the work of the other mosfets that are relaxing with their gate at 0 volts.

So, now I see the purpose of your AND gate. You could have each driver output (limited back down to 5v through a voltage divider? since the driver output is like 12-15v) connect to an AND gate that would disable both drivers somehow or other. Maybe send the signal to the micro-controller, and based on a number of possibilities, the microcontroller has an enable line that gets ANDed with the PWM signal, whos output goes to the mosfet drivers! Git 'r done! hahaha!

You are some kind of crazy Maguyver with your wood based motor controller! I love it!

[MPaulHolmes]

Even though I think it's a tiny bit irresponsible, on ben's next prototype, but oh well! I think it will be fine! I ordered some different diodes, that are rated at 600v and 80 amps each instead of 200v and 60 amps each. They will have a bit more heat loss, but that way I can still use a single mosfet driver, they only have 2 legs instead of 3, so there's less soldering (better opportunity for THROUGH H0LE SOLDERING!) and then crazy ben can adjust a variable resistor to change the hardware current limit all the way up to maybe 700 amps. 800 would be the absolute max, but I think that would be irresponsible with 10 mosfets/diodes. hehe. Oh OK! If you want to try it BRIEFLY!!!!!!! But there is a real danger at that point of frying something before the heat spreader has a chance to do it's duty.

That's the nice thing about the LEM current sensor. It measures all the way up to 900 amps, not that we would need to do that.

[edown]

Hey, Paul. That was pretty much what I was thinking..
I wonder, if you can take the outputs of 2 optocouplers and put them in series to make an AND-gate, then, your driver board would still be isolated from the controller board?? You would still need a voltage divider to drive the optocouplers, I think..

I'm glad you like my "cheesy” controller, I was just so glad to have it work even better than I had hoped.. I’ve blown out 4 IGBTs (300 and 400A) and a pile of mosfets, just thru ignorance..

[MPaulHolmes]

Originally Posted by edown

Hey, Paul. That was pretty much what I was thinking..
I wonder, if you can take the outputs of 2 optocouplers and put them in series to make an AND-gate, then, your driver board would still be isolated from the controller board?? You would still need a voltage divider to drive the optocouplers, I think..

I'm glad you like my "cheesy” controller, I was just so glad to have it work even better than I had hoped.. I’ve blown out 4 IGBTs (300 and 400A) and a pile of mosfets, just thru ignorance..

Oh Stinker! I forgot about the isolation! Good point!

I burnt up a pile of mosfets too! I kept them all in a box, because I sort of felt bad, but I moved on, and threw them in the garbage. ahhahaha! They started to stink. No, but seriously, they were like $5.50 each and it made me really sad that they broke, a whole string at the same time. That sucked. I wanted to open them up, and somehow fix them, but I knew they were gone. boohoo!

[blowncurtice]

Paul, I am still following your thread, I started back when you built the mini to power some LEDs. I am running a 1985 Camira with a 9" Advanced DC Motor at 144 volts, for the first two years I struggled with lead acid batteries then about 6 months ago I bought 45 90amph lithium (about 145 volts) about a month ago I blew my Curtis and ordered a Logisystem controller which should arive tomorow. I would like to build one of yours as a project and I would then have a spare.

[MPaulHolmes]

Hey Blowncurtis! hehe. That's a great idea! Very very very very very very...
very soon all the details will be layed out in gory uh... detail. I just spoke to one of the most wonderful people in the whole universe that is doing the PCB layout right now!! LIke now as I type! He sent me some screen shots of it. I'm sort of excited. Sort of really really really excited. really excited, actually. Once some PCBs get made, it will be relatively straightforward to do the control section, and then the power section will be not too bad either! Heck ya dude!

Then we will be able to power an LED! haha! An LED that can be seen from PLUTO!