# [Electronics] Pulse triggered relay/switch



## ste2425 (May 31, 2013)

Ive started this here as it's electronics related even if the application is not for computers.

*Back story don't need to read.*
Basically its late and my minds been left to wander and ive thought up a method of implementing a crude but should be effective method of creating an alarm for my car. Due to it having remote central locking but not running on a CANbus system (a digital method of communicating between devices in the vehicle) I cannot simply buy a CANbus alarm add-on module. So my central locking works by two wires going to each motor, one goes high and the other low to lock and swaps to unlock. My idea is some form of relay, ill call this relay X, that is triggered by these two wires and holds its state. This is in-line with the battery, relay X, door switches or ignition and car horn in that order. So when the car is locked relay X is activated creating a circuit. But the circuit is only complete when either the ignition or door switches are activated sounding the horn. When the car is unlocked relay X breaks this circuit regardless of if the ignition or doors switches are activated so the horn wont be sounded.

*Problem*
I need some form of relay that will switch on from a pulse from one input and will then stay activated and will then turn off from a pulse from either that same input or a separate one. It will be running from a 12v car battery and so will not need to consume power when its on or off, unlike a conventional car relay which will consume power as long as the relay is activated. So basically its some form of switch that doesn't need a constant input to activate but a pulse to turn on the a separate pulse to turn off.

I hope this makes sense and you guys n gals don't mind helping even if its not computer related. If you need any more info on what im doing with or what it is im actually after just ask. 

Or is there a member on here with a great knowledge of this sort of stuff that id be best PM'ing them?

Thanks all.


----------



## TheoneandonlyMrK (May 31, 2013)

You can buy a relay like you want and its base from RS components for sure possibly maplin

Whilst im still not sure whats occourin your plans seam sound 

Most factory fitted central locking is an alarm afaik.??


----------



## 1freedude (May 31, 2013)

Old school relay...momentary switch activated by movement/position of the lock.  Not sure what the switch will do, but an idea


----------



## ste2425 (May 31, 2013)

1freedude said:


> Old school relay...momentary switch activated by movement/position of the lock.  Not sure what the switch will do, but an idea



the switch or ignition will be the trigger that will activate the horn. If the door is locked relay X will complete the circuit so that if the doors are opened whilst the vehicle is locked or the ignition started whilst the vehicle is locked it will complete the circuit and set off the horn. I then plan fit fit a flasher relay before the horn, same as for indicator lights so the horn beeps on and off.



theoneandonlymrk said:


> You can buy a relay like you want and its base from RS components for sure possibly maplin
> 
> Whilst im still not sure whats occourin your plans seam sound
> 
> Most factory fitted central locking is an alarm afaik.??



Great stuff ill have a look over there. Do they have a specific name?

Sadly no the alarm was an optional extra the original owner did feel they needed  I could try and find the original alarm module and its various gubbins but they quite hard to come by and expensive.

Edit:

Just realised ive used pic boards extensively on my uni course, for DSP though. Should be too hard to pick up an Arduino board for this, just needs to monitor a couple of inputs see if they are high or low and output to a few relays. Easy peasy


----------

