Pixhawk Zener diode - a stiff brandy and assistance required - Discussions

A quick call for assistance regarding connecting a Zener diode to condition power on the Pixhawk servo rail.

Our Vulture 2 spaceplane's Pixhawk (seen above in testing bodge installation mode) takes juice from the power module as per usual, and we've got the second output from the module hooked up to RC8, with the servos connected to the rail (in the photo, only the two canard servos are connected). The reason for this hook-up is that we're powering the entire system from four Energizer Ultimate Lithiums, and that works fine - to a point.

The servos are very jittery, and Andrew Tridgell said we might need a Zener diode, which appears to be the case. Our expert in these things is on holiday (or in hiding), so it's left to me to resolve the matter. However, having read this (http://copter.ardupilot.com/wiki/common-pixhawk-wiring-and-quick-start/#Connect_RC_inputs), I am none the wiser as to how exactly to hook the diode up. I've got a couple of the recommended 1N5339 diodes on order, so if anyone has already tackled this, some guidance would be appreciated.

Replies

iskess June 1, 2014 at 10:34am

Looking at the wiki where you found the diode part number, It appears you simply bridge the +5v to ground using the diode. This can go on any set of pins on the servo rail as they are all connected as a single buss. The black ring goes on the ground side.

I don't know why 3DR doesn't include a diode laden servo plug with the Pixhawk, or at least sell them as a huge markup.
- Lester Haines > iskess June 1, 2014 at 11:00am
  
  Yes, that makes sense. So, it's just the diode connected across two pins of a servo connector and plugged into the bus. Thanks.

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