TRex Resetting by itself? Help!

We have a TRex Jr controlling one dual motor gearbox (Tamiya 70097) on the Pololu round robot chassis. The power source is 6x AA NiMH (2000mAH). It is controlled by a 4 channel RC receiver.

Earlier, we had it setup per the instructions at a slow gear ratio (203:1) and it was working.

Later, we changed the ratio to 58:1. The car goes faster but is jerky and hard to control. During some trial runs the car fell down from 4 inches.

Today, we put on a servo that was rated for 4.8 volts on the receiver as well. When we tried it out we smelled smoke and this is when it started to reset every time we tried to move the car. A few minutes later the TRex started reseting even when we didn’t move the joystick.

What happened and how do we fix it? Please help!

-Miller Winners


Are you powering your RC receiver off of the TReX Jr (i.e. is the BEC jumper in place)? If so, this could explain the smoke and subsequent problems. The BEC jumper uses the TReX’s regulated 5-V line to power any receiver connected to a channel input. This line is capable of supplying perhaps around 100 mA, which is more than sufficient to power a receiver. However, if you connect a servo to that receiver, you are now trying to pull perhaps an amp through a regulator that is not rated to dissipate that much power. My fear is that the smoke came from some component of the TReX Jr’s regulation circuit that could not handle this amount of power dissipation.

If you disconnect everything from the TReX Jr except for the battery, does it still exhibit this constant resetting? What if you just connect the motors but no servo? If the TReX Jr seems to be damaged, you can send it back to us and we’ll take a look at it.

- Ben

Hi Ben,

Yes, we’re using the BEC from the TRex. Didn’t know about the power limitations.

We tried it out this morning. When we powered it on, it was showed only solid blue; neither
the red nor the green flashed. :frowning:

We took off the motors, same, solid blue only.

The motors tested out ok, they work fine.

Ok, we’ll send it back. Can it be fixed easily?

-Miller Winners

Can you confirm that you had the BEC jumper in place when you connected the servo to your RC receiver? Knowing this will better help us diagnose the problem.

We won’t know how difficult it is to fix until we see the unit. If it can be easily fixed, we will repair it and send it back. Your RMA number is 38767, and you can find our address here. Please display the RMA number and your contact information promonently on the return packaging or on a packing slip. Once we receive the unit we will contact you to let you know if we can repair it.

- Ben


The BEC was on for sure. There was no other RX battery used.

-Miller Winners