What Diode for DC Motor?

lardom

I've been building circuits since 2007 so I know I shouldn't 'have' to ask this question but I don't know the answer so I have to ask the forum.
What diode should I use for a DC motor @12volts and @20Khz PWM? On some projects I mix DC motors and servos at different voltages. Add to that a wireless module at yet another voltage.
I bought some optocouplers to isolate my Propellers until I figure out what I'm doing wrong. I have been experimenting with six to nine volts to power my motors but I want to scale up some of my projects to 12 or 24 volts.
Can I solve the problem with better diodes?

tonyp12

So what is going wrong? The Prop resets itself?
Does it look like motors create ground bounce that raises the ground floor to high that it create a BOR?

Tree Power (with inductors and caps) and Star Ground is design goal.

lardom

The problem goes back a few months. I posted a question because I couldn't figure out why I wasn't able to get a clean square wave at 20Khz. I had just bought a cheap oscilloscope that let me see the PWM. I remember Tracy Allen asking me to test different i/o pins. I suspected that he was onto something so I swapped out the Prop and the problem disappeared. Someone thought I could have destroyed the PLL.
I had used that Propeller to drive two 9 volt DC motors, four 5 volt servos and an RF module @ 5 volts. I cannibalized that board so I can't give a lot of details about it...but I have been afraid to connect any motors to my Propellers since that time.
I want to be able to wirelessly control a machine that has DC motors 'and' servos that I can scale up in size and power. My thought is that if I had the proper knowledge I would not 'have' to use opto's. Even though I'm not an engineer I should know this stuff after twelve years of building circuits.