Auxilliary servos on receiver? How To?

12 years 3 months ago #26938672 by artwait
Hi,

Well, I just fried my AX2550 and want to learn the best way to avoid this next time. Here's what I did:

The controller had been driving two wheelchair motors on my robot quite nicely. I was using a 4-channel RC for commanding the motor controller. Everything was powered with two 12v batteries in series.

Yesterday I decided to make use of the two extra, unused channels in my RC receiver to drive a couple of servos on my robot. I connected the servos to the receiver and powered everything up (note that I do not have a separate battery connected to my receiver--it's powered by the AX2550).

The servos worked for about 30 seconds, then one of the servos stalled and I got the ubiquitous "pop" and smoke from the back of the controller. That was that.

Soooo, obviously next time I don't want to be drawing too much power into my receiver from the AX2550. What's the best way to wire this up so that I can get the power I need to the servos without blowing up my controller?

Thanks!

Art

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12 years 3 months ago #26965858 by cosma
Replied by cosma on topic Re:Auxilliary servos on receiver? How To?
The 5V out is for powering relatively low power and "electrically quiet" devices like and RC radio or microcomputer.

An RC servo will take a lot of current with spikes when turning on. It looks like it created chatter on the 5V which in turn must have put the controller in an unstable condition.

The rule is never to power an RC servo from the controller, or from a receiver that is powered from the controller.

You need to provide a separate 5V to the servo.

If you still want to have the radio powered from the controller, then you must cut the red wire that goes from the servo to the radio. Then connect the red wire from the servo to the + of a separate 5 to 6V battery. The - of that battery must be connected to the controller ground (pin 5 or 13 on the connector, for example)

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12 years 3 months ago #26972116 by artwait
Replied by artwait on topic Re:Auxilliary servos on receiver? How To?
Thanks for the response.

So, perhaps an easier way to handle all of this is to power the receiver separately (and have it then power the servos). What's the recommended way to do that? My understanding from the documentation, is that I should not connect a separate battery to the receiver as it may send current into the controller and blow things up...

Thanks!

Art

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12 years 3 months ago #27013763 by cosma
Replied by cosma on topic Re:Auxilliary servos on receiver? How To?
You can power the rc with an external batery but if you do this, you must not have that battery voltage going to the controller. If you are using the supplied RC cable, you simply need to cut the red wire on the loop that comes out of the connector shell

Otherwise, just make sure that your radio has only the ground and signal wires going to the controller.

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12 years 3 months ago #27207835 by Darrell
Replied by Darrell on topic Re:Auxilliary servos on receiver? How To?
Wow. I was about to do the same thing. Can I power my extra servo from a power board I'm also using? It has both 12v and 5v I/O lines on it. The same 12v batteries feed power to this board.

Darrell

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