Circuit breaker pops

[chadrubino]

Hello - RV-10 installation, per the book. D-100, SV-42s, pitch and roll, AP-74, 5.3 successfully loaded. During flight test, heading hold works ok for a few minutes, but when giving it about a 10 degree heading change, AP circuit breaker pops. I've got a 2amp CB for the AP. Install guide says to use an appropriate sized circuit breaker and also says servos can draw 2.03 amps at 100% torque. Suspect I need to put in a bigger CB; both servos can draw up to 2.03 each, and AP-74 needs 2amps as well? Or I can dial down the torque a bit, or use one of the inner holes on the servo mounting arm? Am I going down the right path? Suggestions on what size CB is appropriate? What would you do?

 

[dynonsupport]

A 2 amp breaker for a 2 amp load (4 amp if you have two servos!) is not an appropriate breaker size.

We try to stay away from turning our manuals into full-fledged electronics manuals, but basically, if you have two SV42s (2 amp max loads) tied into one breaker, you need to have overhead. For a single SV42, a 3 amp breaker will suffice, and so for two, a 6 amp breaker (if you can find one in that value, which I didn't see quickly at Spruce) would be fine.

You can always go bigger, of course, as long as your wire is capable of handling the load. Remember that breakers are fundamentally protecting your wiring from burning through things in case of a short. So, you always need to make sure that your wire is sized appropriately for the max load that it's expected to be able to handle (the breaker value).

The AP74 uses milliamps. You can bundle it with the servos.

 

[peter.braswell]

On a flight this weekend, I experienced the same thing - a fuse popped in flight and shut down both of my 42's. I figured I had under-sized the fuse.

Although I understand you guys wanting to stay away from being a full-fledged electronics tutorial, an example like you included in this post would have been very helpful. Additionally for folks such as myself who are using your servo harness (wires included) it seems like it would be completely appropriate to go ahead and specify breaker/fuse specs.

Thank you,
Peter

 

[PhantomPholly]

Here is the simple answer for electronics-challenged folks like me:

Circuit breakers are there to protect your WIRES, not your EQUIPMENT.

In this case, a 5 amp breaker for two 2-amp servos is probably fine, but if not I believe they make 7 1/2 amp breakers. I think there are also "fast acting" and "slow acting" varieties - if using a 5 amp breaker, just go with "slow acting" and you will keep the smoke in the insulation.

You can only let the smoke out once...

 

[TRCsmith]

You can also use an auto fuse block with the correct fuse. I see you have an RV 10, so you maybe can afford the aircraft type. Just a thought  http://dynonavionics.com/public_html/yabbfiles/Templates/Forum/default/wink.gif