Quote:
Originally Posted by gralewicz
Have you published the schematics?
We have been looking at the same mod at the Milwaukee Makerspace and are thinking of going 1 step further and re-designing the openrevolt board with both MOSFET and IGBT drivers laid out.
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The TechShop locations near San Francisco have laser cutters. Perhaps the Makerspace locations do as well. Laser cutters are great to cut solder stencils from inexpensive mylar sheets (overhead projector transparencies). They aren't as good as professional stainless steel stencils, but work fine for hand assembling a few boards with parts down to 0.50mm pin spacing.
Once you can build with surface mount components, you have many great parts available.
We designed our motor controller around the STM32 microcontroller, which has CAN bus, a fast A/D converter with 16 channels, and very flexible pinouts. The controller is run fully isolated, with a Si8421 isolator to the CAN transceiver and a DC-DC converter. The gate driver was on a second board with its own DC-DC converter and a Si8233 isolating gate driver chip.
The interface between the two was the logic-level PWM output, and a 5V supply for the input side of the Si8233. This design makes it easy to switch power stage designs, but was really motivated by our use of counterfeit IR MOSFETs bought on eBay from a Chinese vendor. These bogus parts kept blowing up power stages and gate drivers, and having the gate driver on its own board made it easier to swap and rebuild.
My next design will go back to putting the microcontroller and gate driver on a single board, with both referenced to traction voltage. That allows the internal ADC to directly measure the operating voltages, and opens up many opportunities for better reporting and diagnostics. For instance, accurately detecting the end of precharge, monitoring inductive spikes, and detecting desaturation.
Putting the microcontroller at traction voltage makes *almost* everything simpler. Most signaling already takes place over CAN bus, where the isolation is easy and inexpensive -- the Si8421 adds about $1.25 in parts. The only tricky points are the emergency contactor and the throttle wiring. While the software can accept a CAN throttle (untested), we still use a Bosch TPS. The wiring for this needs to be marked as being at traction voltage.
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