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Old 12-30-2008, 03:10 AM   #53 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Low Power half finished and working!

We finished the low power half of the 72v motor controller. It is tested and working! The circuit was completely separated from the STK500 programmer, and is now on a breadboard (a practice circuit board that you can plug wires into). The wimpy PWM signal from the ATMega8 micro-controller was connected to the input of the big beefy IXDD414PI gate driver. That sucker can switch on and off lots of mosfets REALLY FAST! I measured the output of the gate driver, and it puts out a PWM signal where the low is 0 and the high is 12v now instead of 0 to 5v (which is what it was coming out of the micro-controller).

So, I guess you could say we now have version 2, a 12v 14amp motor controller, a pretty big jump from version 1 (the 5v 0.01amp motor controller). However, the 14amp could only be sustained for a very short period of time.

The next step is to hook up a single mosfet/diode to the power board, and maybe only run it with a single 12v battery. I'll hook it up to the bike to see if the wheel spins. Once a SINGLE mosfet/diode is included, we will officially have a 72v 20amp (continuous) motor controller!

There's a little problem with the oscilloscope. It only reads up to 20v, so we need to get a 10x voltage probe, so we could read up to 200v.

That big dang beefcake hunk of SOLID 1"x2"x8" aluminum will be the heat spreader. It's WAY overkill for the bike version of the controller, but whatever. It's all good. This is supposed to be practice for a car! The car version will use the same size aluminum heat spreader (maybe slightly longer than 8 inches though).

Going from 0 to full throttle takes a minimum of 5 seconds (even if you slammed your foot on the gas pedal), and if there was some sort of shutdown, it also takes 5 seconds to get back to full throttle (after it moves out of thermal shutdown) if you keep your foot all the way to the floor on the gas pedal.

In a couple days, I have to go back to teaching! Time is running out! Does anyone know where I can get cheap LEXAN (plexiglass) pieces? Maybe a few like 0.5"x9"x7" or something? I hear that makes a good box for the controller. Can you drill and tap plexiglass?
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kits and boards
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