Thanks for posting your projects and asking and answering all these questions. I'm an electronics noob and have learned a lot.
This is a really great thread because it contains everything you need to make a basic PWM arduino mod with resistance measuring for variable watt.
Could you do temperature control with this type of resistance measuring as well (voltage divider)
At the moment I'm driving a 3034 direct from the PWM pin at 980Hz, just for initial testing. I'm not bothered about burning $3 arduino out at the moment, I've got loads. It makes a noise when it's firing so I'm either going to have to go up in frequency out of hearing range (32kHz) or down to 122Hz and it sounds like down is the way to go.
Is that a logic level mosfet? I've bought some IR IRLB3034PBF to play around with. From what I've learned it's essential to use a logic level mosfet.
My other question is if the coil has to be considered an inductor? Is the effect neglectible or should you take this into consideration somehow? Can there be voltage spikes from this? Should I use a "freewheeling diode" across the load?
I've tried to use online inductor calculators and it said 0.18uH for a 14 wrap coil and did a simulation with LTSpice and it showed some largish voltage spikes. A schottky diode would improve efficiency, yes?