Let's Make Robots!

TRex Jr Motor Driver and FA 130 motors




I just got these products and I am trying to build an RC controlled robot. I have the TRex Jr controller and the Tamiya dual gear box with FA 130 motors. I hooked the TRex up to my reciever and configured it. I did a test with the LEDs and everything seemed to be working fine and I was getting a 5 V signal out of both motor outputs. When I hook up the FA 130 motors (with .1 uF capactiors across the leads) the drive LEDs flicker and the motors make a high pitched noise and do not turn. When I hook the motors directly up to a power source they turn normally. I realize the FA 130 motors are designed for 3 V operation but I was under the impression they would work fine with a 5V input and just have a shorter lifetime. 

 I am clueless as to why my motors aren't working. I know these motors have high current draw but the TRex Jr is supposed to be able to supply 2.5A to each motor which is above stall current for these motors. Does anyone have any suggestions? 

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

The battery was exactly the issue. Thanks everyone for the help. Now that I have the motors spinning I will try to get the thing all together tomorrow and put it up. I upgraded to the NiMh I had and the motors spinned. It is good to know that the high pitched noise is caused by not getting enough power to start the motor turning.

Thanks again everyone. 

No such luck with the 10uF capacitor. Same result as with the .1uF.
yeah, then just try hooking up a 10uF or so cap in series with the motors
The LEDs are surface mount on the TRex motor driver board and I have yet to find a schematic for the board. So I have no idea what configuration they are in and I don't really wanna mess with the board itself. I might just try some different motors. I have some more on order that take a lower current, but they won't get here for another week. Thanks for the suggestions though.
motors are weird sometimes. Have you tried putting the motor and led in parallel?

I have em hooked up without any wheels at the moment .. just the motor because I wanted to verify that it turns under no load. I'll have to see what capacitors I have lying around. How much bigger do you think would be needed?

 I thought it might be a current issue after I had read some about them on this site, but was confused since supposedly the TRex can supply 2.5 A  which is above the motors stall current.

Have you tried hooking up the reciever to a servo to see what sort of motion you are getting out of it. It may be that it's just not getting a high enough signal. I used to make motors do that high pitch sound with my rc setup when I would give it just enough throttle to get the juice flowing, but not enough to make it turn.

Have you gone through and calibrated the board yet?

Are you using a fresh set of batteries for the motors? are you using a rechargable batter?

can you connect the battery direct to the motor and verify that it turns?

Do you have an image of how the setup looks. That might help with this.


I don't have any servos around at the moment so I am not able to do that. I just started into robotics and most of my stuff is currently on order. These were the first parts to arrive. I calibrated the board and I am using a 9V battery to power the board at the moment. I might try going to a 6V NiMh I have lying around.

The motors turned being independently powered.

Also, no images yet sorry.

Edit: Actually, I think the battery might be my problem. I didn't even think about looking up how much current a 9V could source and I doubt it is enough to drive these motors. I will check that now. 

hrmm...the manual says you can manually calibrate the device, have you tried that as well?

not sure what else to try at the moment.

Yes it was calibrated. I got it running by using my NiMh. I feel stupid for not thinking about the current sourcing of the 9V battery to start out with. Luckily I had a 6V NiMh that is working with the motors. Live and learn.