Control of a 24v20


some time ago I bought a 24v20 motor controller and now I finally found the time to start working with it. I am planning to make an Elevation controller for a parabolic antenna driven by a 24V(max 8 A) DC pushrod actuator for radioastronomy.
In order to control the 24v20 I am planning to use the PWM ports of an atmega1284P to control PWM, DIR and RESET of the motor controller. FF1 and FF2 should either go to LEDs on the case for manual intervention or (probably better) to the microcontroller and cause an immediate low on PWM and RESET.

As the motor controller (24 V) and the uC (5V) have independent power supplies, is it ok to just tie the grounds together or should the motor controller be attached via an optocoupler (LTV847) and a second one for bringing the fault flags to the uC?

The plan at the moment is to put the uC, Motor controller and a 24V Power supply in a metal project box, and grounding everything. The whole thing might also be connected to a computer via USB if one wants to run an observation program.

As my professional background is not in electronics, I’d be happy for some pointers; not wanting to fry either the 24v20 or the atmega…

Thank you very much.


You can and should tie together the grounds of your microcontroller and motor driver. You can also directly connect the signal pins from your microcontroller to the motor driver.

By the way, your project sounds cool! Do you have a blog or a website with more information about it?


Hi Jon,
thank you very much for your help, I appreciate it.
I haven’t documented the project further yet, as it’s very much a work in progress.
The basic idea is the following (now somewhat out of date):

(Replace uC by Atmega1284P and the motor controller by the 24V20)
In a first step, only elevation will be controlled so the idea is to use an accelerometer (invensense.comMPU-6050) attached via I2C (P82B715 to allow a long cable) to determine the elevation.
We have no idea whether that will work or not, but I made a board with the necessary interface chip and level shifting MOSFETS. I am now working on a first version of the controller on stripboard.

I will update here when I have any news or questions.

Thanks for sharing; good luck on your project. We would love to see pictures of it when it is finished!