Bypass a push button as a power supply

Projects General Guidance
2

Not real clear what you are trying to describe. However maybe you just need a simple relay that the arduino turns on and off and the relay contacts are wired across the two terminals of the switch that presently opens your door. Does that help?

http://www.ebay.com/itm/New-1-Channel-H-L-Level-Triger-Optocoupler-Relay-Module-for-Arduino-5V-/221409246814?pt=LH_DefaultDomain_0&hash=item338d04fe5e