Four diodes can be a bridge rectifier.2*AC to solenoid, + to supply, - to ground.Leo..
When you say "2*AC" what does this refer to? Not AC as in AC vs. DC ?
Could have a resistor in the 12volt line to the "reverse current relay", for a lower reverse current.
But MarkT's circuit with a DPST (or DPDT) relay should actually work just fine...
The diode limits reverse voltage across the coil to 0.7volt.
I don't like drawing higher currents (did the OP ever say how much?) thru NC contacts, most relays I've ever replaced that were switching motor current had the NC contacts burned or welded.
The last time I ran a powered up test and had my meter hooked in-line ... seems like the magnet was pulling maybe .5 amps.What I do know is that it was like .1amp over what the USB output of my computer was rated for so that was the point I decided that the magnet needed it's own power supply.
I am powering the magnet with 5volts stepped up to 12v through a small (eBay special) amplification circuit.
I will also add that, while using that same power supply to provide the reverse power spike does simplify things somewhat (one circuit to rule them all) ... 12v is WAY overkill for what is required to eliminate the Remanence.
I really am curious as to how little it will take. We already know that .7volts from a AA battery was more than sufficient. I may spend my next bit of bench time, setting up and testing that.
The diode limits reverse voltage across the coil to 0.7volt.Leo..
Well, an AA (Alkaline) battery gives 1.5 V, not 0.7 V. But if 0.7 V is sufficient (and you do need to double check that measurement), then that is also the voltage across a power diode if you specify the "crossover" resistors accordingly.
BTW - the resistance of the magnet is .064ohms. So subtracting the probe resistance gives me a reading of .056ohms
And what current would flow if you applied 12 V to .056ohms?