3v0
I take what you say on board and agree 100%, not just because of the potential failure, but also because of the amount of time troubleshooting a home made anything that just doesn't seem to work right.
In this case however, I'm talking about an old surplus single board pc that cost me $50, so I'm willing to give it a try. The worst case scenario is not going to be disasterous and it will be a good learning tool for me.
I am a complete novice when it comes to this stuff, having the skills to solder and my experience being limitted to building kits from detailed instructions, often without success, so... Hero999 would it be possible to give a noob a bit more information on the modifications you suggest?
I think I can build the circuit as shown in the diagram, and I'm ok with putting a 15v zener across the output terminals, but where should I be putting the one between the gate and the MOSFET?
Thanks for all the advice everyone, it's been really helpfull.