'02 Door Lock Mechanism Question

[ntegan1]

Hello Aurora community!

I have recently taken an interest into implementing an RFID scanner for locking and unlocking my car doors as an experiment for my '02 aurora. So I took apart my driver's door lock mechanism and messed around with the wires behind the lock/unlock button.



If I connect wires 1+3 with a jumper wire, the car unlocks. If I connect wires 3 + 2 with a jumper wire, the car locks. These findings were reinforced with ohm readings of the lock/unlock switch while disconnected from these wires. With my multimeter, I believe that I found wires 1+2 to be ≈ 5V (4.67V), wire 3 to be ground, and wire 4 to be ≈ 12V (11.23V).

My question is this, you aurora-owning electricians, What would be the best way to control these lock/unlock wires with a microcontroller? Possibly a SPDT relay such as this?
www.sparkfun.com/products/100

[wfooshee]

The lock works by applying ground from 3 to one of the other wires, 1 or 2. The 12V wire is there for the light in the button. The voltage you're seeing on the other lines is not really voltage supplied to the circuit, but what is present on the inputs of the body control module so it can detect when a ground is applied.

When #1 is grounded, you are requesting an unlock from the body control module, and when #2 is grounded, you are requesting a lock. The body control module decides if it's OK to do it, i.e. do not unlock if the car's in gear and moving.

This is not something you want your RFID circuit to hold, i.e. keep #1 grounded while your RFID is in range.

The lock/unlock button does NOT directly affect the locks, it's an input request to the body control module.

(There are actually very few buttons or switches in these cars that directly control their devices; reading lamps and power windows are the only ones I'm sure of. Even the driver's window goes through a controller, though, for the auto-down. Everything else is a request to a black box somewhere.)

[RCA1186]

sall

[sall]

You would need to tap the wires as if you were installing a remote start/keyless entry. Those wires should be easy to locate. Tapping into the wires at the unlock button will likely cause security issues. I installed a Remote Start/RFID Keyless Entry/Push Start on my Classic. Standalone adaptable RFID systems have a very short range and are useless for anything but a swiping action.