After some analysis with the oscilloscope I was able to see an inductive type pulse every time the high torque servo was activated. This made me realize a had a few problems:
- The main power supply wires were too thin probably causing lead inductance.
- The large servos even though they probably have a double h anti flyback circuitry are unable to control regulation spikes from the main power supply. The large current draws cause a sort of switch bounce and the Atheros part seems very sensitive to these pulses.
- The Yún DOES NOT come with a voltage regulator. This is stated clearly on the product page and that is the reason I never saw this on the Yún shield + Uno arrangement I had prior to purchasing the Yún. Perhaps this is the root cause, but all of the above were not helping.
Solution:
- Changed the power feed wires to 18ga
- Added a small Pololu S7V8A regulator and power the Yún and all the electronics from that.
- The servo power now comes from the main power supply with 18ga wire before the electronics regulator.
- Added a 100uF Electrolytic Cap to the input of the electronics regulator.
Everything works perfectly now and in fact the Yún seems much more stable on the WiFi side. I think that anyone using this should add a small local up/down adjustable dc-dc regulator such as the S7V8A until Arduino comes out with a Yún that includes power regulation circuitry.
Cheers,
Alex