I am trying to design a fuel injector driver using Arduino. I am however having trouble deciding how to arrange the flyback diode for the energy collapse at the injector turn-off (typically a 60 V voltage spike). A fuel injector is essentially a 9 mH inductor with 15 ohm resistor in series drawing about 1 Amp of current.
The maximum switching frequency in this case will be 100 Hz (driving MOSFET with an Arduino).
Tried to search the internet but did not get my answers.
Here are my problems: (also adding attachments)
PROBLEM No 1. :
4 injectors - 1 bigger MOSFET OR 4 injectors - 4 MOSFETs
I guess this one is up to my choice
Problem No 2. :
Flyback diode arrangement.
As far as I know, the circuit on the right is a Zener diode allowing the injector to discharge quickly, but to me, it seems a little dangerous, as not all power supplies can sink current. (2nd picture)
Problem No 3. :
Use 1 bigger diode OR 4 separate diodes?
This is the most important one for me. Not sure if using 4 diodes provides even distribution of the current, I feel like it would be a mess. (1st picture)