Car Central-Locking System

For a few pounds you can buy a kit from any automotive accessory shop that will allow your car to be fitted with a central-locking door system. Such a kit essentially comprises a number of motors. There is also a control unit that enables the whole system to function. Here we show an example of such a unit.There are 5-wire motors and 2-wire motors. The 5-wire version is used in doors that have a key-lock.There are 2 connections for the motor itself and 3 connections for the sensor part (an ‘open’ and a ‘close’ contact). These sensors determine whether the door is to be unlocked or locked. If there is no key lock in the door, these sensors are superfluous and a 2-wire motor can be used.

Resistors:
R1,R5,R10,R14 = 4kOhm7
R2,R13 = 22kOhm
R3,R12 = 10kOhm
R4,R11 = 47kOhm
R6,R8,R15,R16 = 15kOhm
R7,R9 = 2kOhm7
Capacitors:
C1,C2,C5,C6 = 2µF2 25V radial
C3,C4 = 10µF 25V radial
Semiconductors:
D1-D8 = 1N4148
T1,T2 = BC547B
T3,T4 = BC557B
Miscellaneous:
RE1,RE2 = PCB mount relay, 12 V, 1 x changeover, size 19x15.5x15.5 mm (e.g. Conrad Electronics # 504289)
PCB, order code 040060-1 from The PCBShop