Hi,

I do not understand fully want you meant. But try if this can be useful.

Put a small magnet on the door. Put a reed switch some inside the vending machine.

When magnet comes near the reed switch,it closes.
When magnet goes far from the reed switch, it opens.

Well, the power supply is at your disposal. Because reeds can handle from 1mA to 3A and sizes are from 5mm to 52 mm respectively.

Hope the answer is relevant and I have not wasted your time as well as mine. Hah Hah...

Visit :- www.reed-sensors.com, www.gunther-gmbh.de, www.hamlin.com,www.cotorelays.com for info on reed switches.

Regards,
B. Gauthaman
India
(New Member & Its my 1st day)