I may be a fairly new member, but I have alot of electrical knowledge that I can share.

Zener diodes are what Serum is referring to. They act like a normal diode until their specified or higher voltage, then they conduct. Unfortunately, they have a slow "response" time to conduct. That time delay still creates spikes.

Schottky diodes conduct ultra fast, but conduct like a normal diode. They conduct one direction, but not the other. Not good for speed controls that have reverse, cause you will have a short on reverse.

The best thing I've found to use on most little motors is something really simple and cheap. It can usually be found for free, conducts at around 80 volts, and is bi-directional..... a neon bulb. You solder it across the motor terminals. Simple, but it works.

Actually, Rene told me he was talking about "Trancil diodes". I never heard of these, but it sure sounded like he was talking about zener or avalanche diodes to me. I did a search and came up with nothing. Have you heard of Trancil?

When a neon bulb conducts, isn't it still a relatively low current device since it's just ionizing a gas? If so, I wouldn't think it would have enough of a shunting effect...

I've never heard of a "Trancil" diode, but it is possible that it may just need translated.

Anyway, most high voltage spikes from collapsing motor fields (especially on sub 30 volt motors) can reach spikes of several hundered volts, but are extremely low current (In the micro-milliamp range). 99% of speed controls use FETS that over the years, the designers have come up with extremely effective ways to control output harmonics, spikes, saturation, etc. I still advocate the use of snubbers in any circuit where you control a magnetic coil. Any time you remove voltage that the mosfets don't have to deal with, you increase the reliability of the device.

Does TVS suppression do anything in our situation? Probably very little. Thousands of speed controls are in use every day without failure, but I use it on mine.

Yeah, it's transil.. my bad.. it's a kind of an avalanche diode..

Most FETs, especially ones for PWM motor applications use a reverse biased zener/trancil/avalanche diode to shunt that reverse polarity spike over a certain value to protect the FETs.

Off topic, but somewhat related, story:
I once had an unknown inductance coil that when used with a simple oscillator circuit powered from a 4 AA batteries produced over 1,000v from the collapsing magnetic field! Felt like a cattle fence! :036: I had it set up so it charged through a resistor over several seconds and then dump the voltage all at once to a set of pads outside a project enclosure. The best part is I put a sign on the box that said "Don't touch" and left it unattended on a table. You can imagine how many yelps I heard. :017:

ahhahahahahahahahahahahahahahaha thats funny, if i were there i'd be one of them

It was pretty funny. Since it was at home, it was the kids doing the yelping. I would just say "The box TOLD you not to touch, so why did you?". So not only did they get zapped, I added insult to injury by scolding them for it. :)

Perfectly safe though since the current was miniscule...

talking bout smoking a mm controller...would it be safer to run a ubec or simply put a RX pack with the internal bec disabled?

If over 2s/6 cells; yes. Although, most linear regulators simply shut down when they get too hot.

Welcome to the forums BTW!