Garage door position indicator

I use to get home late on my bike, and every time I'm affraid I did not close the garage door, or have it accidentaly open by pushing the garage remote's button in my pocket. I made simple indication for this purpose.

Hardware

Main circuit

Main circuit is made from two NE555 timers generating alternating current (two, so it is really alternating, not only pulsing DC). Output from this circuit is fed to garage door switch.

Switch

Switch is located at the bottom of the door, so when the door is closed, switch is engaged. It consists of a togggle push button and two diodes. In each position, one diode is selected, effectively selecting witch half-wave of alternating current passes (positive or negative)

Indicator

Indicator is very simple (this is why rest of the circuit is "so complicated"). It consists of one resistor and two antiparallel LEDs - red and green. It is connected in series with switch and main circuit. As the switch allows passing current only in one direction, normally only one LED lights. Red means door open, while green means closed.

Full-bridge 555 as AC current source, door switch as half-wave rectifier, LEDs as polarity indicators

Internet-enabled

Other indicator is made, very simillar to previous, but instead of LEDs, optocouplers are used. Optocoupler is connected between +5V and DCD of USB-RS232 adapter. This adapter is connected to MikroTik router, watching for serial line change and posting this state to HTTP server.

Software

Simple php application is made - MySQL DB stores history of garage door positions and renders web page with garage door position and history table. Also, plugin for graphic terminal was made, to show icon for garage door on home screen and to show it fullscreen if door is open.

Garage door icon on terminal screen