I wanted a garage door opener that wouldn't need to change batteries and could stay hidden, not making rattle noise while driving.

While searching for an idea, I found a capacitive sensor on ebay that could work pretty nice behind the car dash. This instructable needs basic knowledge in electronics, if you need any help feel free to ask, or you can use www.google.com.

Bill of Materials

1 - Garage door opener remote (Already programed)
2 - Capacitive sensor, that you can hide wherever you want and it has the sensitivity necessary. I had luck finding an Omron E2K-F10MC2 on ebay for $17.
3 - Perfboard or similar
4 - Eletronic components

1x L7812C - Positive voltage regulator
1x CMOS 4011 - Quad 2-input NAND gate
2x 1uF 50v capacitor
1x 10K ohm resistor (Observation at schematic)
1x 0.5A fuse
Optional - 2x2 male Header Pin, 1x Jumper
Connectors, fuse holder and wires

5 - Electrical tape and double sided tape

Step 1: Schematics

The circuit is very simple, it uses the car battery as input power (you can use the 12v line from cigarette lighter). The energy goes through a fuse just in case of something wrong, then I used a voltage regulator to hold the energy spikes from engine start (If you ignore this part you will burn the remote control).

The sensor and remote control are connected to the filtered 12v line, the signal from sensor goes by CMOS inverter, it can be cascaded depends on NO/NC sensor, the CMOS output should be able to drive almost any remote control that uses 12v battery. For a remote control that uses lower voltage, you can use an voltage drop circuit.

Step 2: The Mess Is Made - Soldering the Components

Plan the schematic on perfboard and connect everything with solder, another technique is to use "Wire wrap".

The remote that I used is very simple, it has a push button that closes with +V from the circuit, the purple line on pin 2 of the CI is the same line from the output of the switch (When pressed, the switch drops the voltage to 0v at pin 2 of the CI).