I'm working on a circuit to control a 12V 4-pin PWM fan from an Arduino (that bit is working), and from a source of up to 42V.
Turning the fan off is what I'm having a problem with. I know some 4-pin PWM fans turn off when there's no PWM signal (type B & type C) but the fans I have must be type A as they run at minimum speed when there's no PWM. Given that I might only be able to get Type A fans, I'd like to have an option to turn the fan off via mosfet or similar.
The best 12V step-down that I can find seems to be the Pololu D24V10F12 but that is only rated up to 36V (and 1A), but it does also have an enable pin which solves the turning-off problem.
Although that will probably be fine, ideally I'd also like to have a footprint on the board for something that will work up to 42V (from solar PV), and it looks like Pololu have/are going to discontinue their older model D24V6F12 which goes up to 42V/600mA.
The Traco TSRN 1-2450 step down looks like a good but expensive option as it's rated to 42V, but it doesn't have an enable pin like the Pololu does, so I presume I need to add a MOSFET too unless there's a better option?
I've done some reading and am happy adding an N-channel MOSFET to the Traco's ground line (e.g. stp55nf06), controlled directly from the 5V Arduino, but I'm not sure that ground line what I should be cutting. I guess my questions are:
Is that Traco and MOSFET combo a good option or is it overkill? If it is a good option, can I use an N-channel on the ground line or do I need a P-channel on the input, or can I use an N-Channel on the fan's ground line instead? I'm not sure whether that would mean the Traco still consumes some power.
Thanks and apologies for the long post! Danny