Interesting proplem with Sonar and Motors

DiablodeMorte

So, I'm continuing my work on my UAV blimp. I've gotten sonar(for altitude) working and the motor(s) working and I was all set to get them working togethor when I ran into an interesting phonomon. I'm using the MaxSonar Sonar Rangfinder and the FAN8200 motor controller. The MaxSonar is very much like the PING))) and the FAN8200 is simply a double full hbridge. When I ran the code without the motor attached to the FAN8200 it ran fine. When the range came below or above the specified interval it attempted to turn on the motor. When I finally added the motor I got quite a different response. The reported range fluctuated wildly and I had to pull the motor and then the ranging went back to normal.Note: the ranger is siting right next to the motor, but even about 1 foot away this still happens. Any ideas on what this is?

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Robot Control Via Skype API - Dev Stage(50% Complete) - Total(25%)
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Graham Stabler

Try some suppression capacitors on the motor to to reduce noise, that would seem the most likely cause of a problem. Also ensuring the power supply is noise free under the load of the motor may help, some capacitors on the output of regulators etc.

Of course moving air can effect sound and the motor makes a noise itself so you might also try putting some sort of cup around the ultrasonics to shield it. You need to do some testing to rule out the various possibilities.

Graham