Two part question: I have a Trex Jr, which until earlier this afternoon was working fine. When we went to add a second channel I’m guessing we shorted something, but I was hoping for a sanity check. Right now it will go through all the phases of learning and acknowledge that it has one channel with a green followed by four reds. (or any other combination, provided it is only one channel - it will not acknowledge the second no matter what configuration we use) Anyhow, since then, we cannot get it to power a motor (which was working earlier and still works when tested independently) nor can we get it to learn two channels – however when the same rc outputs are connected to standard servos, they both work perfectly. (And we have it in RC mode, I checked.) So my questions are, 1) any idea why it will learn a channel but not power a motor and 2) why it will not learn the second channel?
thanks very much,
Are you only saying this because things aren’t working, or do you have some other reason to believe you might have damaged the board while making connections? Can you describe how you had everything connected when it was working properly and anything that has changed since then?
The easiest way to see what’s going on would probably be to use the TReX Configurator Utility. Do you have a USB-to-serial adapter you could use to connect the controller to your computer or an oscilloscope you could use to look at signals while they’re connected to your TReX?
I said that because I think the learning mode jumper got connected while the board was powered. Not quite sure, as there were many hands involved. Would that be enough to cause this? Otherwise, we had an RC input coming into channel one, the RC mode select jumper in place, and I think the BEC jumper. There was also 5V into the central motor line, and outputs to the two motors on either side.
I’ll check out the Trex Configuration Utility, thanks.
Adding the learning mode jumper while the controller is powered can damage the controller, though I don’t expect it to result in the kind of problems you are having now.
What do you mean by the “central motor line”? Are you instead talking about the middle column of channel pins? You could definitely break things if you supply 5V to these pins while the BEC jumper is in place, because you are effectively shorting your external 5V power supply to the controller’s internal 5V bus, and the two are likely to be at slightly different voltage levels.
Nope, I’m talking about the row at the bottom where power is input and output to the motors. Screw-ins, not pins.
That should be ok, but note that you’re right at the lower limit of the TReX Jr’s operating voltage range, and you could run into trouble if the current draw from your motors causes the power supply voltage to drop. What is your power supply and what is the stall current of the motors you are using? Have you figured out anything with the configurator utility?
thanks for the help. In the intervening period we ended up switching to another robot in the lab, as the primary focus was the software, not the hardware.