Tackle Interference When Using RF Receiver Relay to Control DC Motors

Motors are used everywhere to move objects forward and reverse, such as in garage and gate openers, curtains etc. thus many customers use our two channel receiver SR-RCS-202U’s built in function to control DC motors forward and reverse. While it should be simple in most circumstances, sometimes you may experience shorter remote range or un-responsive of receiver, especially when the DC motor is carrying high load, and there is high current flow in motor.

This is normally known as radio interference caused by DC motors, especially brush motors with high current load, the difference between DC noise and regular interference caused by same-frequency transmitter is, the DC noise is full spectrum interference, which interferes not only remote control working at 433MHz but also your radio etc. remember the noise bed in spectrum analyzer? when there is DC motor around, it just rises the thresold of noise bed and submerged the valid signal. thus causing the remote distance be greatly reduced to only near-field operating.

Despit the radio interference, DC motor also has interference on the power line, causing noise be transmitted to around electronic devices by power wires, this is known as a common mode interference.

The following are some methods to trackle with DC motor interference, methods including motor improvements and noise filtering.

Motor improvements

Since DC motor noise is likely to reduce greatly for longer range, so the first thing we should do is to place receiver and transmitter as far as possible from the DC motor. as this is the easiest method.

And what we can do more in motor part is to make sure the motor noise has been shielded by metal cover, and the metal cover is properly connected to ground, as a ground shield will greatly reduce the possible RF noise transmission generated by motor circuit.

If possible, consult your DC motor maker for other alternatives that is known generating less noise, such as brushless motors with a good design, while motor design can greatly reduce the noise generated by DC motors, sometimes it is not always feasible because of the type of motor is already chosen or budget is limited, in this case we have to work around to improve on existing design.

Noise filtering

It is possible that when the main noise is caused by common mode interference, we can use a low-pass filter employing simple LC circuit to filter the noise.

Above are two basics ways to reduce DC motor noise, and the noise should be minimized to low level if the motor has proper shielding and the common mode interference is filtered.