How to implement and control electromagnets in sorting machines?

I am planning to make an escargot sorting machine by using electromagnets. Picture below is a part of the conveyor. So initially the magnet holds the plate in place. Then after we put the escargot on the tray, the magnet will demagnetize after some period of time so the escargot can be dropped into a specific tray. After the escargot has been dropped, the tray will return to its initial position and the electromagnet will then turn on again to hold the tray. The timing for the magnet to demagnetize depends on the weight of the escargot (the heaviest escargot will fall first, while the lightest will drop at the last). Do you guys have any idea to control the magnet so it can be demagnetized at specific timing, depending on the weight of the escargot? I've rarely worked with electromagnets before so I'm a bit clueless here. And which electrical components do I need? Any kind of help would be appreciated. Thank you in advance ?.