door lock motors

[l1ttle_d3vil]

just wondering how the motors for door locks work. these are aftermarket ones, not factory motors or anything. they've got two wires coming off them.

if I connect wire #1 to an earth, then put 12v to wire #2 it will unlock.
if I swap it around and earth #2 and put 12v to wire #1 it will lock.

when these are connected to an alarm/remote, does the alarm automatically switch it around so it locks then unlocks? or do some motors only unlock or something?

and one other thing; should they have 12v constantly then the alarm earths it, or should the motors be earthed constantly and the alarm or whatever is controlling them gives 12v to unlock?

cheers
-matt

[Alex B]

Usually have a control unit. $35 from Jaycar will get you a 2 door with master switch, control box and an actuator for the other door. Don't think the 4 door ones were much more expensive.

Alarm will usually be a low current output so you will want a relay to sort it all out. Can probably just use the 2 wire jobs you have if you only want it to work off an alarm, would still need the relays (if they are both 2 wire then you won't be able to manually lock the drivers door and have the rest lock with all 2 wire motors though)

[Ae92typeX]

As you suggest in your post, 2 wire systems do indeed switch polarity for lock/unlock. Generally when going through a central locking unit or alarm they get the 12v signal for about .2 seconds (from what I have read, Ive never tried to time it lol). There is no constant 12v sitting there when not in use, just a earth signal off one wire or the other generally.
However, on some units I have worked on, there is a 12v constant (again swapped between lock/unlock) and just a earth trigger.

As above, if all 2 wire then some systems have a seperate microswitch on the drivers door to control the lock/unlock function with the central locking ecu.