Electrical Noise Reduction

18 years 10 months ago #2376724 by jimsal
Electrical Noise Reduction was created by jimsal
I've been using Futaba 4YF with no problem but I'm trying a Futaba 2DR(much less expensive) and am experiencing short range, jerky operation, and sometimes short delay in response. In reading the manual I understand these symptoms could possibly be electrical noise.
On page 29 of the AX2550 users manual "Electrical noise reduction techniques"
1. "keep wires as short as possible"
I read that you shouldn't lengthen the wires, but is it ok to trim them shorter? And would trimming them reduce chance of EN? It would actually be convenient for me to shorten the wires as all my components are close together. I have been connecting the motor power wires (green & white) to the motor wires then folding and tying them to the steel frame. Could the folding cause problems?
2. "Loop wires thru ferrite beads."
What are ferrite beads?
3."Add snubber R/C circuit at motor terminals"
What are snubbers?
4. "Keep controller, wires, and battery enclosed in metallic body"
You want to elaborate on this? Do I need to totally enclose these units in a metal box?

One more thing. My receiver is in an aluminum box padded with foam from the controller packaging. The rec. is only about 2 inches from the top of the controller. Could this cause any problems ?

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18 years 10 months ago #2378822 by cosma
Replied by cosma on topic Re:Electrical Noise Reduction
The first thing to do is to find a way to objectively measure the quality of the transmission.

An easy way to do this is to plug a common RC servo in a spare channel on your receiver, if you have one. A faulty/noisy communication will cause the servo to make noises and jump around.

Then observe the communication quality with

1- everything off, except the radio receiver. This will give you the best possible quality you can hope for
2- controller on, motors stopped (joystick centered). This will tell you if the MCU clock circuit is making the offending noise.
3- controller on, trying to move the motors but with motors disconnected. This will tell you if the noise comes from the switching MOSFETs, radiating in the wires
4- controller on, motors moving. This will tell you if the noise is due to the motor brushes, although noise will also come from the switchim MOSFETs and wires.

As for the techniques:
1- shortening the wires can only help but there is no guarantee it will. Do this as a last resort as it is a non-reversible alteration.

Folding or coiling wires will alter the inductance and may create noise. Try unfold and move aroud. Observe if this make any difference on the RC servo discussed above.

2- You can see examples of Ferrite filters at dkc3.digikey.com/PDF/T043/0793.pdf. These are now commonly found on power cords of electronic devices to keep the noise from radiating from the cord. It is not clear how well they would work in this case but would be worth trying.

3- Snubbers are just an RC filer that you put near the motor. You would need a capacitor of about 0.1uF and a resistor of about 10 ohm (~1W) in series. This assembly would be connected on the motor wires as close as possible to the motor itself.

4- Keeping the receiver away from the controller is always a good idea.


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