My MOSFETs keep getting fried (is that the sophisticated technical term?). Basically, I'm using it with an Arduino to switch a higher voltage. The load is non-inductive. At times, because of moving things around, the connection to the load sparks at which point the MOSFET no longer switches off the source/drain. One time it destroyed my Arduino (fortunately just a $10 SparkFun pro mini) so I'm assuming that time gate/source was fried.
It needs to be able to handle getting that spark. How can I protect the MOSFET from getting fried in this situation? I've commonly seen schematics with an inductive load (small motor) where there's a diode in reverse parallel with the load. I've also seen schematics where there is a diode across the source and drain, and ones where there's a diode across the gate and source, but don't know if those are applicable here.
What configuration would be appropriate for my situation? I'm guessing it's both the diode across source and drain and the diode across gate and source, but that's just a guess and blind testing could get expensive. Also, what type of diode? Zener? Schottky? Ordinary diode? Thanks!
non-inductive ? and you have sparks ? Even a wire of 1 meter can be inductive.
I think you don't have to protect the gate, but always use the fly-back diode over the load.
You can also add a diode across source and drain, if unknown things are happening.
Did you have a shortcut, so that the mosfet shortcuts the power supply ? Not much you can do about that. Perhaps you can use a 100A mosfet, if your power supply is 4A.
You have to know about grounding. When the grounding is wrong, a spark from a load could creep back to the Arduino and destroy it. You can avoid that with a relay or optocoupler.
Can you tell us more ? Your post is full of unknown things. What is the higher voltage, what is the load, which mosfet, and so on.
Hi, can you post us a copy of your circuit, either CAD or picture of a hand drawn circuit in jpg, png or pdf format
This way we will be able to see what you are talking about, do you have a fuse or breaker on the higher voltage, how high?
Also what is the part number of your MOSFET?
Sparks pump all the high frequency oscillation modes of your wiring and load
rather effectively - expect at least double the supply voltage to hit the drain terminal
if this happens, so a device rated at 3 times the supply might be needed.
Also if there is enough inductance then the voltage will be higher... long leads have
inductance proportional to their length (twisted pair or shielded cable is the
lowest inductance).
If there is any way you can stop sparks happening, that is the preferred solution,
sparks radiate tonnes of EMI and are a nuisance for that reason alone.
If not then a snubber network across the sparking contacts can quell the high
frequency components - a suitably chosen C and R in series is the usual snubber
arrangement, matched to the load.
