FET driving

bfgstew

Senior Member
Can 1 output pin drive 4 of these IRF510 FET'S?

Basically I want to see if it is possible as I would like to free some pins up, I have the 4 FET'S on individual pins at the moment. they drive 4, 12v solenoid coils that have 30 ohm resistance, sorry but I have no data sheet for the coil. I have them as per the schematic in manual 3 page 24.
Is it possible off 1 pin? Or can I drive the 4 coils off 1 FET?

Stewart
 
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rq3

Senior Member
Can 1 output pin drive 4 of these IRF510 FET'S?

Is it possible off 1 pin? Or can I drive the 4 coils off 1 FET?

Stewart
Maybe, just barely, possible. The IRF510 is an old, inexpensive MOSFET designed for a gate drive of 10 volts. It will turn on when driven by a Picaxe to 4.5 volts, but will typically carry only about an amp at that gate drive. Since your 4 coils will need 1.6 amps, driving all 4 from one MOSFET isn't likely. You might be able to drive 4 gates from one Picaxe pin, but you won't be able to do it very quickly! Those MOSFETS will certainly need good heatsinks, as they will be operating in their linear region (neither fully on nor fully off).
 

bfgstew

Senior Member
@rq3 Thanks for that, they are only going to operate 3 times for about 200 to 400 milliseconds each time. So would a different FET be advisable and if so which would be the best option?
 

premelec

Senior Member
If you have a bunch of similar non-low level FETS you can tie their gates together and drive them all with one pin [there will be higher capacitance but still very little current going from the drive pin into the paralleled gates]. Then one relay per FET drain. There would be a little timing skew but likely not much... As hippy sez - a low level FET would do the trick if you can get one...
 

bfgstew

Senior Member
@e
@premelec

Thanks to you both, the easiest method for me at the moment would be to tie the 4 gates together driven off 1 pin and have the 4 coils going to the respective drains, timing shouldn't be to much of a concern but will test it out before tryng to find and purchase some more FET's.
Cheers guys.

Stewart
 

Paix

Senior Member
Rapid free delivery.png
This might help somewhat on the Rapid Electronics front. £10 before VAT spend only required for the next few days, so not as big a burden as having to spend £30 (£35) before VAT.
 

bfgstew

Senior Member
I tried the first suggestion of having all 4 FET's off one pin and by jove it works, so I have succeeded in feeing 3 pins up, hooray.

Thanks guys for the input.

Stewart
 

premelec

Senior Member
Glad it worked - I hope you put a resistor in series with the PICAXE and 4 Gates to limit the peak pulse current to the gates to less than 20ma - 5v/.02 -
resistor 270 ohms or more should do fine... otherwise you may have some unexpected glitches from the initial too high drive current to the gates... We don't want glitches now - do we :-0 [won't show up until inconvenient!]
 
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