[Al Skierkiewicz]

Don,
Years ago we set up StangSense to measure current in motors. It used a one foot length of #10 wire in the negative lead of the speed controller input. Using a Maxim battery charge monitor IC we could scale the voltage dropped across the wire into a current through the wire. 100 amps in a one foot piece of #10 generates 0.1 volts. You will have to search here but I am pretty sure we uploaded the schematics. We used StangSense to alert our drivers when they were pushing too hard and to analyze other teams robots. Our software plotted the battery voltage, and motor current against time ticks provided in the IFI controller and then displayed them on a Palm. We then were able to download the Palm data and generate a spreadsheet and plot. In odd situations, we merely played back video of the match and timed out to our high current demands to plan on software changes to prevent the IFI controller at that time from reboot. The old IFI controller which did not have a backup battery, dropped out below 8 volts. We regularly saw small drops into the 4 volt range as motors turned on in drive or pushing. If you want more range, move to #12 and the voltage drops goes up to 0.160 volts per hundred amps. It is a little harder to scale but it is possible.