I’ve got two different chassis that I’m trying to drive using a TREX Jr board and the same remote control. On the smaller chassis, everything works like a charm. The LEDs fire in the direction I want to go and the chassis gets a move on. On the larger chassis (a 4WD Arexx wild thumper), when I move a stick on the remote control, both direction LEDs fire at the same time, and apart from a high-pitched noise, nothing happens.
Is this noise coming from the motors? There is no immediately obvious location to put the capacitators, as the leads of the motors aren’t easily accessible. All motors work fine if I directly connect them to a power source. Any hints on how to fix this?
The TReX Jr is not an appropriate controller for the Wild Thumper because it will not be able to deliver the current your motors are trying to draw (the max current for the motor drivers is 5 A, which is less than the stall current of just one of the motors on the chassis). If you lift the chassis so that the wheels are free to spin in the air and if you very gradually increase the commanded motor speed, do the motors start to move? By the way, it is normal for you to see both motor direction LEDs on at the same time; during the driving portion of the motor PWM, the correct indicator LED is on, and during the off portion of the PWM, the current circulating through the motor lights up the LED corresponding with the opposite direction.
For your Wild Thumper chassis, I recommend using our higher-power TReX or a pair of SMC 18v15s.
Hi Ben,
I’m aware that the TReX Jr is a poor match, but it was the board I had around. I expected the chassis to at least move. I doubt the motors are pulling > 2.5 A for the empty chassis, though. Between the motors and the board, I’ve added a set of quick 2.5 A fuses, and they haven’t blown yet. The motors turn fine if I directly connect them to power bypassing the board, but not the fuses.
Thanks for clearing up the mystery of the direction LEDs, that nicely explains why I wasn’t seeing this without a motor connected.
Thanks for the pointer to the SMC 18v15, I managed to miss that on my initial search. Oh well, looks like I’ll be playing with the TReX Jr on the smaller tracked chassis for now.
One thing you could do is check to see if the controller is reporting any motor faults. My suspicion is that the inrush current of the motors either triggers the drivers’ built-in current-limiting functionality or causes it to register as a short-circuit fault. This could happen faster than it would take your fuses to trip, and in either case, this could keep the driver from ever being able to get the motors started moving.
