I own an Alfa Romeo 75 car and I have fitted an alarm. Unfortunately Alfa decided to make the doors switches opposite to usual. When the doors are open they supply 0v GND (ground/negative) and when shut they supply 12v GND. So this makes it difficult to hook up to my alarm as it wants a 12v GND or 12v POS (positive) supply when the doors are open.
So not being that savy with electronics I figured I could get by with 4 relays (with NO/NC terminals), one for each trigger wire. I could not use one as there would still be 12v supplied if the other doors where shut and only one was opened. I rigged these up but as you would expect they chewed through the cars battery power pretty quickly as the coils were nearly always active because as you realise doors spend most of their time shut!
I went to a local electronics shop (JayCar) in Geelong, Australia and the person behind the counter recommended the following circuit layout.
**broken link removed**
(Also attached below)
I have put his suggestion together, but I am not getting the reaction I had hoped for. The basic idea of the above circuit is that if door switch 1 or 2 or 3 or 4 are not switched/pulled/toggled/on/down/together then the NOR gate will tell the transistor to switch the relay on or off. Where the lamp is hooked into the above circuit the alarms positive door trigger wire would be hooked up in the actual application.
I hope that I have given you enough information to help me come up with a circuit that works.
Thanks in advance,
Simon
So not being that savy with electronics I figured I could get by with 4 relays (with NO/NC terminals), one for each trigger wire. I could not use one as there would still be 12v supplied if the other doors where shut and only one was opened. I rigged these up but as you would expect they chewed through the cars battery power pretty quickly as the coils were nearly always active because as you realise doors spend most of their time shut!
I went to a local electronics shop (JayCar) in Geelong, Australia and the person behind the counter recommended the following circuit layout.
**broken link removed**
(Also attached below)
I have put his suggestion together, but I am not getting the reaction I had hoped for. The basic idea of the above circuit is that if door switch 1 or 2 or 3 or 4 are not switched/pulled/toggled/on/down/together then the NOR gate will tell the transistor to switch the relay on or off. Where the lamp is hooked into the above circuit the alarms positive door trigger wire would be hooked up in the actual application.
I hope that I have given you enough information to help me come up with a circuit that works.
Thanks in advance,
Simon