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Rc battle bot


Im starting a new project
A battle bot using 2x7.2volt motors and Pololu TReX Dual Motor Controller DMC01
Plus a servo flipper arm
But not know what size battery do my run time is 30 mins any ideas


Hello, Primewing.

I don’t see any reason you cannot use a 7.2V battery pack to power your motors and the TReX. You should check the voltages your servo can take since it might be as low as 4.8V. If your servo’s operating voltage is less than 7.2V, you might consider a step-down regulator to reduce the voltage.

You might find this blog post helpful in determining what capacity battery pack you should use for a 30 minute runtime. You will need to figure out the combined current draw of all of the devices in your system to do that calculation.



Is most likely going to be a 20kg servo volt range 4.8 - 6.6volts
It’s a mid range bot
If the volt range is as stated will I still need a step down resistor


It sounds like those servos might draw a lot of current, so it might be relatively hard to find a regulator that can source enough. I suggest checking with the manufacturer to see what the stall current of that servo is. You might take a look at our higher current step-down regulators or consider a separate battery source for the servo that is within its voltage range.



Servo stall current is 2710mA at 6.6v


Something like our D24V22F5 5V regulator might be okay to power your servo.



just wiring up trex dmc01 but I have no motor led appearing
help anyone


Can you suggest what I have done wrong here, no led to tell me the motors are working



It looks like you have the learning mode jumper installed. While the learning jumper is installed, the TReX motor controller will not run the motors. If you have not already, you should calibrate the TReX to your RC receiver using learning mode. Once you have done the learning mode, you should remove the learning mode jumper. You can read more about the jumper settings and learning mode in the TReX user’s guide, which can be found under the “Resources” tab on the product page.



Simple answer to a unnoticed mistake
Thank you


This is the prototype phase of my first rc flip bot
Tank steering single stick control
But how would I connect a servo ( for the flipper arm)
Via a relay using the second stick on the rc control correctly



If you plan on using an RC hobby servo, you could just connect the servo to your RC receiver. If you do connect your servo directly to the RC receiver, you will need to remove the BEC jumper and connect a power supply that can provide enough current to your RC receiver.



The hobby servo sg5010 6v
So a 9v battery sure do the trick plugged into the bat. On the receiver and remove the bec won’t cause me any burn out of components


So in short I can run two batteries
One for the board
One for the servo
But what about the receiver is connect to the board is that why the bec is recovered


What would cause the cable from the board to the receiver to fry, I ask coz I just fry all 6 .
Good news board and receiver both still work ?


The cable might have been damaged by too much power going through it. Make sure there is not a short or incorrect connection in your system. If you post pictures, I might be able to give more advice.

The reason you cannot use the BEC jumper with a servo is that the typical RC hobby servo draws about 1A of current, and the 5V regulator on the TReX cannot supply that much current. You also do not want the 5V regulator to conflict with your separate power supply. You can use separate batteries for the TReX and receiver (with servo attached), just make sure that your supplies are appropriate for each use.

By the way, a standard 9V battery is not an appropriate power supply for the TReX or servo. 9V is too high for most servos and could damage the electronics inside. In addition, standard 9V batteries cannot provide enough current to run most motors and servos.



I looked over the circuit after I message yourself
I know what I did wrong and I think I was luck not to brown out anything else
I try splitting the power from the main battery to the receiver … not my best idea …
Going to re wire the circuit to make sure I haven’t damaged any other cables …
I will stick with two batteries with one safety links and a on/ switch for the receiver
( keep it’s safe for all components)