I am looking at using a IRFL014NPBF to turn a 500mw 12v supply on and off, the trigger coming from "digitalwrite HIGH" on pin 10
Can anyone advise on the circuit layout.
Thanks in advance

Data sheet available here

You can't its not a logic level MOSFET, despite the 'L' in the part number. Its a poor performer too,
to say the least. Find a part thats 0.02 ohms or less at Vgs=4.5V, there are thousands.

Thanks for reply, it was a case I have a few hundred laying around :frowning:
What about a optoisolator between ground and pin 10
Or can you recommend something better ?

In addition to what MarkT said, just how were you thinking of connecting this? That is an N channel which is usually used as a low side switch (between the load and ground). If you try to switch a simple linear type supply "off" by disconnecting ground with your FET, the output will tend to go to the full 12v not zero since it has lost it's ground reference. A high side switch would work to disconnect the 12v input, but you can't drive the gate direct with digital write to do that.

What I am trying to do is switch the load on and off via a sketch which I have already compiled, the load has nothing to do with the Arduino. I was planning on powering the Arduino on its own dedicated 5v supply and the load on its own dedicated 12v supply, effectively a software controlled relay. If that makes sense

You missed my point - an N channel FET is turned on by taking the gate above the source voltage (Vgs) - if you are trying to drive it direct, that would mean the "source" pin has to be connected to ground and the "drain" to something you are trying to pull down to the ground level. If you are trying to switch the 12v into the supply on and off, you need either a P channel FET (with a driver circuit) or and N channel FET but to drive the N channel one, you would have to also have a driver circuit to take the gate above the 12v supply line to be able to turn it on. Do a search on "FET high side switch" for more information on what I am saying about level shifting.

My goal is to improve on the attached commercially available circuit that uses a pic16f8i8 i/p with two resistors in series that triggers the IRFL014NPBF to output the 12v. I am replacing the Pic chip with a attiny 85 If I powered the attiny with 12v and let the attiny 5v regulator power the board, would that make it easier to switch output from the IRFL014NPBF.

Thanks for everyone's input, I have been out of electronics for over 12 months due to health issues and let's just say the grey matter had gone to mush.
The simple answer to my quest was sat on my desk in front of me the whole time, the humble L298N Dual H Bridge ! I need to switch 3 12v supplies in different combinations, with the L298N having 4 switchable outputs I have a spare