Trex one motor turns the other does nothing

I am using the Trex in my 1/16th Tank, 2 can motors w/ capacitors installed, 7.2v 3300mah battery used.
I believe the Trex is set up in tank mode ( this is what I was looking for ). Forward, Reverse, Left, Right.
I am using an RC Rx/Tx to control the Trex. When I am at just less than 1/14 stick forward
the right turns, the left side does nothing. When i get to about 1/2 stick both right and left turn however
right seems to be turning faster.

Many moons ago i went thru the steps of calibrating the Trex to the best of my abilities and at that time
all seemed ok, for some reason the calibration has been thrown off, i don’t why.

How can i recalibrate the Trex and is there a way for it to retain these setting at power down,
or disconnect.


The TReX does retain its calibration values (they’re stored in non-volatile memory, so they aren’t lost when the unit is turned off). When you last calibrated your TReX, was it for the same RC system you’re using right now?

What you’re describing does indeed sound like a calibration issue. You can recalibrate your TReX by following the steps in section 3.e of the user’s guide. Please let me know if this solves your problems.

You can also use the TReX’s serial connection to adjust the calibration values manually. The TReX configurator utility for Windows gives you an easy way to adjust all of the TReX’s settings should you want to tweak the ways the different motors respond.

- Ben


ok i did recalibrate and many times too just to make sure I was doing it correctly.
There is an improvement forward stick now control both right and left motors going forward great !
but there is still a slight problem, the right wants to pull more then the left does.
From neutral giving a little stick the right side moves first, a little more stick forward then the left moves.
The right wants to always move first and slightly faster then left. this is after calibrating many times just to make sure i got right.

During calibration i am removing mix jumper. applying the SO_GROUND jumper and
cycling the sequences.
After calibration i am reapplying the mix jumper ( for tank running ) and removing the SO_GROUND -> TX/RX

Like i said an improvement but not perfert, both right and left motors do not want to move in unison.

I have the TREX configurator - can i use the USB Orangutan programmer to interface the TREX for tweeking ?
I could use a standard RC cable to connect the Orangutan to the Trex (Tx/Tx/G) , and do you carry extra
pin headers? i will need to solider a 3 pin header to the Orangutan to connect an RC cable.

Calibrating the TReX for your particular controller means that it learns the ranges of the signals the controller is putting out on its channels so that it knows what neutral is and what the extremes are. It then maps the signals so that one extreme becomes “motor forward full”, the other extreme becomes “motor reverse full”, and neutral becomes “motor stopped”. Unfortunately, you can still have asymmetries in your robot’s behavior if the two motors it uses behave differently (maybe one has more internal friction, less resistance in the motor coils, etc). For example, now that you’ve calibrated your controller, both motors might be getting the exact same outputs from the controller (as desired), but the two motors could react differently to these outputs (not desired).

One way to fix this is to manually calibrate your TReX parameters until you can get the robot to go straight. The parameter I suggest you try tweaking first is PWM maximum. By default, this value is 127, which means that any speed 127 and over results in full motor speed. Decreasing the PWM maximum will make the motor spin faster for the same control stick position, and increasing the PWM maximum will make the motor spin slower for the same control stick position. I recommend you lower the PWM maximum parameter for the right motor (the one that starts turning first and pulls harder) until the two motors behave the same way.

You can use the Orangutan USB programmer as a USB-to-TTL-serial adapter. You will need to use the shorting block to put the programmer in adapter mode (i.e. short the two pins labeled with a “U” on the underside of the board). Then connect TX on the programmer to the TReX’s SI pin, RX on the programmer to the TReX’s SO pin, and G on the programmer to the TReX’s ground pin, G. With these connections in place, you should be able to talk to the TReX using the TReX configurator utility. The utility isn’t well documented, but it’s fairly straightforward to use. Please let me know if you have any problems getting it to work.

- Ben


Thank you.

It seems i have other issues going on here. My left gear box might have a bent shaft
as you suspected it is not always electronics but mechanical

I’ll be a while working this out, but If do have to resort to manual settings for the TREX,
and if i have questions i’ll let you know

thank you so much for your help.