Long story short...
Two T'Rex motor controllers have stopped working. The first one failed without any obvious cause. The second started smoking while I was driving it in my back yard. Among the possible factors there are at play, I believe that one factor is a bad motor on my Wild Thumper, and another is that the fuses on the TRex aren't functioning properly. Is there a way to reset the fuses or clear the motor faults? If you have any advice or ideas, please share them! I'm new at this, so please forgive me if I've forgotten to provide any crucial details or missed something obvious. Let me know and I'll do my best to fill in the gaps.
T'Rex 1
I got a T'Rex motor controller and a Wild Thumper robot chassis from SparkFun.com. The motor controller stopped working after about 5-10 minutes. I made sure to mount the T'Rex so that it wouldn't short. I used a 2650mAh 3S LiPo. All my wire connections were solid. Jumpers in their proper place: LV Mode jumper out, Switch Bypass jumper in. Here's what it looked like after I'd hooked it up:
For my RC gear, I used a Taranis and the X8R receiver that came with it. It has performed reliably for months on my tricopter.
I had trouble getting started, because the T'Rex wouldn't go into RC mode. I figured that it was checking for an RC signal before the receiver had established a link with the transmitter. By disconnecting and reconnecting power a couple times, I'd get the 3 beeps from the motors, indicating that RC mode has been activated.
I drove carefully indoors, but didn't like my control setup. So I increased the expo on my right stick. I had mistakenly used the left (throttle) stick for vehicle's throttle, so I decided to switch the receiver wires and use the elevator for throttle. I disconnected the battery and turned off my transmitter. I switched the channel wires.
Upon reconnecting power, both Motor Fault LEDs were dimly lit.
Connecting power via USB caused both Motor Fault LEDs to be brightly lit.
I could flash the firmware successfully. The serial monitor showed something that looked like this:
I read this LetsMakeRobots.com thread and the SparkFun comments for the T'Rex. I determined that this T'Rex is faulty, though I don't know why. I contacted SparkFun support, and they graciously sent a replacement.
T'Rex 2
Enter T'Rex 2, who ended up smoking in the backyard grass. Here's the story of her demise.
When my second T'Rex arrived, I mounted it expertly. I used the Taranis' elevator channel for throttle, with the expo jacked up even higher: to 90%. That tamed the beast and made her easier to control.
I drove it around the house for a few minutes. Slowly and carefully. It pulled to the left a bit. Not enough to make me concerned.
I mounted my FPV gear. Awesome. One screw holds my modular FVP setup to the Wild Thumper chassis.
I went to the backyard to drive around. I pretended to be controlling a rover on a different planet. One with lush green vegetation that should have been mowed last week.
I diligently crawled through the grass. I could hear that the motors were experiencing an additional load, but this beast seemed more than capable of tromping around the yard. I drove around on the grass and on my paved driveway. On the pavement I again noticed the tendency to drift left. I tried to fix it by trimming to the right. Didn't help.
I took off my goggles and drove the vehicle toward me through the grass. I drove it around near me for a few more seconds of fun. Then I noticed a whisp of smoke. I immediately disconnected power. I let it sit for a while as I shook off my disappointment.
I reconnected power. No beeps. No motor fault LEDs. Just a dimly lit Power LED. DISCREPANCY NOTE: I wrote the preceding sentences in this paragraph almost a month ago, the day the controller started smoking. I'm not sure if I was mistaken at the time, but now when I connect the battery, the Power LED and Motor Fault LEDs are dimly lit. But still no beeps. When I disconnect the receiver and reconnect power, all LEDs are brighter.
When I connect via USB, the power LED and motor fault LEDs are brightly lit. I am able to flash the T'Rex firmware. The serial console displays output similar to the screenshot above.
Is a bad Wild Thumper motor a culprit?
I thought maybe the fact that the Wild Thumper was pulling to the left might be significant, so I connected a 2S LiPo directly to the left side. I found that the front motor spins about half as fast as the other two. Check out this video to see for yourself. My hypothesis is that this motor is causing a higher load, so the left motors turn a bit slower than the right ones. Since I had no weight on the chassis, the front wheels didn't touch the ground when on a surface like the driveway. When the Wild Thumper was in the grass, that front left wheel made contact, felt the load, and drew too many amps. But even so, mysteries remain: shouldn't the T'Rex's self-resetting fuses have prevented the smoke? Why, on both T'Rexes, are both Motor Fault LEDs lit, rather than just the one for the left side?
I have a few days before my return shipping label expires, so if you know of any way to revive either of the motor controllers or whether I can fix that slow motor, please share your thoughts! Thank you!
https://www.youtube.com/watch?v=kNjgPDR4hig