I am looking for any information that would help me reduce the power rail noise and EMI of DC brush motors. I am building a robot that is powered by 2 x 250 W 24V DC motors.
Thank you in advance
Electronic – Methods of filtering noise caused by DC brush motors
dcdc motorfiltermotorrobotics
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Ok, a couple of things:
- It's pretty much never a good idea to surpass recommended brushed DC motor voltage ratings, as doing so will definitely damage/overheat your motor leading to safety issues.
- If you need to increase your power/torque, the way to do that is to add another motor controller/motor and in your code set them to be equal/inverse.
- I've worked with that motor before, and it definitely should not be drawing >60 amps, even 40 amps is alot. Try using a multi-meter to test current, or put in a 40amp fuse in series with your motor wiring.
- What motor controller are you using? Considering you're using a CIM I assume it's FIRST (Talon, Victor, Jaguar, etc). If you motor was drawing over the maximum current you would not get an "error," rather it would simply stop working. I recommend revisiting your wiring diagram. Additionally, these motors draw a lot of current, make sure your power supply can handle them.
I would love to hear more about your project so I could better understand your issue.
Brushed DC motors are notorious for throwing out EMI (electro-magnetic interference). The PRIMARY solution is to use a good bypass capacitor (like a 0.1uF ceramic) right across the power pins on the motor. AS CLOSE as you can get to the brushes.
Sometimes, with larger motors, it takes additional filtering in the form of shunt capacitors and even pi-filter elements with series inductors...
These photos are from a good tutorial on reducing EMI: http://www.stefanv.com/rcstuff/qf200005.html
Additional bypassing of both power and signal lines is also beneficial. Capacitors can cause sluggish response in sensors if you use too much. It doesn't take large capacitors to be effective in shunting away ("filtering out") EMI.
Shielding and grounding are a "gray art" at best. Halfway between engineering and applied magic.
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Best Answer
The noise could be generated by either the brushes (commutation) or the driver if its PWM. Easiest fix for brush noise (which would be random or 'static') is a capacitor right across the PMDC motor leads, something like a 1 µF, 100 V ceramic capacitor might be a good starting point.
If the PWM supply is causing problems (something with narrow spectral content), you would need a choke between the PWM power rail and your main supply.