It’s Alive (Sort Of)! (Last Post Before Commencement)

I spent this week doing the final mounting and wiring everything up. It’s really tight, but everything fits (pics below).

When I first turned it on, I noticed that there was a short somewhere on the 24V rail. It was only reading 0.7 volts. As a diagnostic, I disconnected the lower current section of the DIN block. That didn’t help. This narrowed the problem down to either the inverter or the PC power supply. I disconnected the PC power supply and the power rail held at about 24V. Now I knew the PC power supply was shorting somewhere, but not where or why.

Opening up the PC case, it became pretty clear what the problem was. I had mounted the power supply inside the case in such a way that the solder blobs on the board for the power input terminals were shorting across the case itself when the lid was on. Duh. I fixed the problem by covering all exposed solder/metal on the power supply board with electrical tape. It’s a bit of an ugly fix, but it works. The proper solution would be to properly mount the thing with standoffs so nothing metal gets close to the board, but I don’t have the right size standoffs right now. I should toss some into the next McMaster order, if I make one. Fortunately, there was no damage to the PSU or motherboard, and everything booted up fine.

Next, I tested the cRIO (booted up fine, but I haven’t checked that the software is responding properly), LIDAR (has power, but won’t know status until I’ve got software running to read the serial output), and the inverter. The good news is that the inverter still powers the controller (I tested this a while ago).

The bad news is that as soon as I enable the motors on the arm, the inverter cuts out. The IRC5 shuts down and doesn’t turn back on until the motor enable is released. The inverter obviously doesn’t have enough oomf to power the motors. I’m not sure if the problem is just that the voltage output of the inverter is dropping too low to power the IRC5 electronics or if the inverter is shutting itself down as overcurrent protection. I’m guessing the former, but I won’t know until I can get a current probe on it and check. In the mean time, I need to start shopping around for a new inverter.

Side news: Wyatt and Greg came down later today to show Abby to the rest of the DARPA Challenge team. They’re apparently discussing using it as a proof-of-concept vehicle. It looks like I may end up involved in this grand adventure…

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