Basic Power FET Question

If you don't provide a current path for when you turn OFF the solenoid, you will be punching through the DS barrier. Many power FETS will permit this for awhile but none will permit this forever. A snubber network of either a capacitor (slow turn OFF), reverse biased diode (fast turn OFF) across the solenoid coil or even a clamping zener diode across the Drain and Source (fast turn OFF) will preserve your FET.

The gate threshold voltage for the IRF510 is listed as 4 Volts so if your 5 Volts is real (not out of a TTL gate or such) then it should be turning on hard enough.

BUT, the Drain to Source breakdown voltage is listed as 100 volts and the back EMF from your solenoid would easily exceed that. I have no doubt that without a reverse diode across the solenoid, the FET will be destroyed when it turns off.

Place a 3/ 6A diode in reverse across solenoid valve or across FET (S & D) will solve your problem. I think when solenoid is switching off the transients are damaging the FET.

So the verdict is inductive kickback... many thanks for your responses.

IRF510 gate turnon voltage should not be less than 10 V to fully turn on the FET, if a voltage beetween 4 and 8 volts is applied to the gate the FET will act as a voltage dependant resistor and will not open fully, it will heat up,

When you turn it off, yes it is a inductive kickback and aa Diode across the solenoide is absolutely necessary

Regards

My mistake. The threshold voltage is that voltage where the drain current is less than 250uA. So 4V is the maximum voltage where turn off can occur.

To turn it on you should have >=10V - I agree.

The reverse diode across the solenoid is still a must.

Also a series blockig diode would not hurt iether.

You would be better off if You COBBLE it together then CLOBBER it together. Couldn't resist this

Just teasing

oilcan13

I would think a "reverse" protective diode should be a given across an inductive load.