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I have a project that requires using steppers motors to work within centimeters from a wireless RF transmitter and receiver. I am using this stepper https://www.adafruit.com/product/858, the transmitter is FS1000A and the receiver is XY-MK-5V.The signal transmitted is a square wave with period modulation.

I can send data between the two chips with two PIC24Fs and I can spin the motors. But I can see the noise on the oscilloscope in the RF signal and every once in awhile (2 in 5 minutes) the signal output from the receiver gets very noisy and then flatlines. I have to reset the PICs before it comes back. This only happens when the stepper motors are spinning.

Is there a way to insulate the stepper motor so it does not interfere with the transmission? Or is there a slightly more expensive RF chips I can use that this wouldn't happen to?

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  • \$\begingroup\$ Earth the case, shorten the cables as much as possible and/or shield the cables to the stepper motor (this will be your highest emission point). \$\endgroup\$ – Jack Creasey Mar 7 '17 at 6:09
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    \$\begingroup\$ Sooo many things that could be going wrong. Post a picture and a schematic of your setup. All sorts of things could help, but if you just stagger into ER, we don't know whether to shock your heart or saw your leg off without an examination. You could try a 10nF cap from every stepper phase to stepper case, plus driving the stepper with shielded cable, bonded to the stepper. A common mode ferrite on the stepper drive could be enough. Or you might need supplies splitting and opto-isolation. If you've poor supply decoupling on your Rx, it might need only that fixing. More information required. \$\endgroup\$ – Neil_UK Mar 7 '17 at 6:21
  • \$\begingroup\$ Thanks for the responses. I am currently working on a breadboard temporarily so my wires from the driver to the stepper are very long. That could definitely be the problem. Question about that: I can shield the wires fine but how do I shield the actual soldered connections to the board? Those soldered connections are very close to the receiver would they be a problem even if I shield the wires? \$\endgroup\$ – Shawn Volpe Mar 7 '17 at 17:18
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For a receiver to tolerate interference, the radio frontend needs to operate at high levels of current and thus have high-levels of BLOCKER IMMUNITY. The price of the radio is not so important (tho more input PI filtering should help, costing more for components and PCB area) as the current drain.

To reduce interference from the stepper motor, create "local batteries" right at the motor/case, to ensure the surge currents are provided locally and thus have no need to travel over long wires. The "local battery" occurs when you implement a low-pass-filter using some series inductance and some shunt capacitance. Where to tie the shunt capacitors? To the case.

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