Ya, you can't go wrong with that setup. Have fun!

Received my new bottom boards but want to try and prevent the issue from happening again with the new boards. I am considering putting in blocking diodes inline with the signal wire. (1N4004 have over 100 in my parts bin)

EZB ------- |<----- Servo

This should prevent voltage going back to the EZB if the servo would short out.

Comments, suggestions.

@rz90208,

What you want to do is called flyback diode.

There are typically flyback diodes on the internal servo control board. You shouldn't need them externally.

If you "really" want to isolate the servos, you will need an Opto-isolator for each servo, some H-bridges use them.

https://www.sparkfun.com/products/9118

tutorial: http://www.electronics-tutorials.ws/blog/optocoupler.html

That is a bullet prof solution, what ever happens in each side does not cross to the other side.

Don't forget you are dealing TTL levels, you are isolating "TTL" levels, a cheap solution to protect your EZB ports (although there is a 330 ohm resistor between the the micro-controller port and the the EZB pin) is a Logic Level Converter circuit.

tutorial: https://learn.sparkfun.com/tutorials/logic-levels

if there is a short circuit, you replace the LL circuit versus replacing the EZB.

Bi-Directional (Low <-> HI): https://www.adafruit.com/product/757 https://www.sparkfun.com/products/12009 https://www.adafruit.com/product/395

or DIY version (single direction): https://www.adafruit.com/product/1787

Note: Both the opto-isolator or the Logic Level require a 5V source to drive the high side (Servo's ttl input signal). You can use a BEC or step-down circuit to obtain 5V from the servos power supply.

@ptp DJ informed me. The servo signal inputs go direct to the CPU, no buffering what so ever.

I have a drawer full of lm324 quad operational amps from when I built my CNC control board.

EZB --- 3v --levelshifter 5v --- lm324 ---- Servo

Servo (805BB) can handle the 5v TTL signal on the signal pin or do I need a second level shifter?

(was hoping to shortcut and just use a diode so it could be inline, no additional boards.)

I like your solution better, as you said bullet proof.

@rz90208 there is a current limiting 330ohm resistor between each servo pin and the MCU. This protects the MCU I/O pins in a large amount of cases, except over-voltage. Unfortunately, a diode likely wouldn't work due to the voltage drop across the diode, taking a 3.3V signal and subtracting the diode's 0.6V voltage drop would leave the signal at 2.7V which is very close to limit for detecting a "High" signal for most chips.

I do like @ptp's idea of an opto-isolator or level shifter. A simple transistor could do the trick as well.

After rereading the thread, DJ did mention the 330 ohm resisters.

So after reading the links ptp posted. (Thank you ptp). I can just use the level shifters low voltage side toward the EZB and do not need the lm324 at all.

EZB --- 3v-LS-5v ----- Servo

for the 5v I can get that from my 6v supply and use a couple 7805 regulators. Can I get the 3.3v from an ADC voltage pin or just use an LD1117V33 regulator off the 6v supply?

keep it simple...

Lower side: get the 3.3V from the ADC bank, both EZB/Iotiny have a very good DC/DC circuit.

High Side: get the 5V using a regulator, you only need a few mA to drive the servos logic, so whatever you have on hand i believe is ok.

bear in mind if you use raw regulator (e.g. 7805) is always a good idea to have capacitor on the output side (stabilize), check the datasheet.

Thank you my Cylon friend. Have the 7805 on hand and ordering 10 - Adafruit TXB0108. That will cover both EZB's I have in my InMoov and a few extra.