Foolproof but basic control of Electromagnet?

[dav888]

Hi,

Looking to control a small "opposite" holding electromagnet.

Most common voltage of these seems to be 12VDC, with about 400mA to release the field.

Ran across this board that just uses a basic mosfet + gpio control. https://wiki.seeedstudio.com/Grove-Electromagnet/
Since available power might be limited and the pulse needed to release the magnet is fairly short, I'd like to find a more foolproof circuit that
- has a fixed pulse-length (tuned with R/C)
- current limited or clamp with safety-off
- soft ramp-control (to be nice to the rest of the system)

Anyone with experience using similar magnets and a discreet or 'ready-made IC' (that isn't for 50W solenoids) that can do the job?

[ledtester]

I have one of those 12V P20/15 electromagnets -- just the bare magnet, not the module.

For what it's worth, inductance is about 45 mH, resistance 50R giving a time constant L/R of roughly 1 ms.

[NiHaoMike]

Use the transistor switching the low side with a diode across the coil configuration but add a capacitor between the microcontroller and transistor so that a stuck high won't leave the coil energized.