RC Input Amperage ratings on the 18v25 MC

I’ve got an arduino that I’m using to provide input into the RC lines of the 18v25 motor controller, and while experimenting with it I managed to burn the arduino out (doesn’t boot, the IC gets really hot when given power, etc).

The only way I know of for this to happen really is to short/draw too much current through some of the pins. It is possible I managed to do this on accident by touching two unconnected leads; but I’m also wondering if it might be that the 18v25 is allowing more current than the 40mA rating of the arduinos IO pins. I was hotswapping the RC control lines before the Arduino burnt out, which maybe wasn’t a great idea.

My questions are a) what is the max current the RC control logic will allow, and b) whether or not there is any possible instantaneous shorting that could happen from hotswapping these control lines.

Kudos on the product itself by the way. I like the hardware and the available software made calibrating our custom Arduino PWM setup super easy. Are there any plans to offer a dual channel motor controller rated for continuous 25A in the 18-30V range in the foreseeable future?

Hello, jdb.

I’m sorry that your Arduino burned out. The Simple Motor Controller 18v25 should not be sinking or sourcing very much current on the RC inputs. Each RC input has a 1k resistor which serves to filter the signal and also limits the current. This is true for all of our Simple Motor Controllers.

There might be little bursts of current when hot swapping your wires, but I would not expect it to burn out an Arduino.

I suggest double checking all your wiring and making sure your ground connections are good.



The SMCs are designed to be easily pairable for mixed-channel/single-stick control of two motors. See the bottom of section 4.3 of the SMC user’s guide for more information. Would this kind of setup work for your application, or do you truly need a single board?

- Ben

Good to know, I’m thinking it was just a wiring short while prototyping against the arduino.

We are essentially doing exactly this setup; except with an Arduino. There is no hard constraint for a single board, but it would be preferable for form factor / wiring reasons. We are going to move to using the USB/serial interface to adjust speed; and so having a single board would also free up a UART on whatever microcontroller we end up going with. It is definitely something we’d be interested in if you offered one.

The SMCs are designed to be chainable on a single serial port, so you do not need two UARTs to control two SMCs. Please see the bottom of section 4.2 of the user’s guide for more information. The existence of the TXIN pin means that the amount of extra wiring to do this is pretty minimal, and it allows you situate each controller closer to the motor it controls, so you can conceivably keep your motor wires shorter.

- Ben