Well, I could look into RFID tags like that, but it needs to be initiated from the door opening, I wasn't thinking about having the base station constantly polling the access points for updates. I will look into it a bit more. I did some research on RFID readers for another project during my senior year of college. I designed a wall avoidance system for a quadcopter and the construction engineering guys wanted to add an RFID reader payload to it to present it as a cost effective inspection platform for large buildings, specifically concrete structures and their RFID tags attached to strain gauges inside the concrete and rebar.
Since you can use them to transmit data from sensors, I guess I could try to have it change its ID based on the status of the door/window. But that means the base station would be polling constantly. Gonna reduce the lifetime of my zigbee.
Mikey T.
Can you use a magnet and a NC reed switch that would open the reed when the door opens allowing a line to be pulled up via a pull up resistor. Use a large enough value resistor so you aren't drawing too much current across it. This would generate an interrupt to the processor. Then the NO side of the reed switch would complete the circuit for the RFID device. Then the processor would poll all the RFID devices to see which one generated the interrupt and will communicate. I guess you would only need one wire for ground. Is this any help?
Yendor
Yendor, I think Mikey is more concerned with how to provide enough power to transmit the door/window status, that just simply detecting open/closed. In any event security systems often don't just use digital open/closed type inputs, the ones I've worked with are analog inputs, and measure the current through the switch/sensor to detect tampering, for example a burglar tries to bypass the switch with a short cct, you can detect that by sensing increased current, just as easily as an open cct.
Mikey, I've used zigbee, in both point to point and mesh configurations, I think you'll find it tricky to get enough power, even with a sleeping end-point configuration. I've only ever used that with batteries, and solar, There are other wireless options, but it depends how far down the track you are with zigbee. If you haven't already committed to zigbee, you might look at wifi using ESP8266 or similar.
Yendor, Solar panels are fully insulated on all sides including terminals, if you were to come in contact with the exposed cabling from a string of panels in series then you'd have to break through an enclosure to do so. The danger of an astronaut on the ISS getting electrocuted by solar panels is vanishingly small. Even if they took the covers of the junction boxes, they are wearing gloves which would provide some insulation. They could climb all over the panels themselves and not get zapped, but, I'd guess they might mechanically damage the panels.