General questions

[Asjad]

Dear All,

My current factory car alarm has some minor limitations which I am confident I can update

A) Does anyone know if there is an industry wide harmony of what
different colour wires do on car alarms?

B) I have decided to take the dashboard flasher as an signal to the PIC, when the alarm is active, any different approaches?

C The problem is the signal on this wire is a continous pulse, how can I convert this into a flatline DC signal to indicate to the PIC that the alarm is active?

Your feedback is appreciated

 

[Nigel Goodwin]

Dear All,

My current factory car alarm has some minor limitations which I am confident I can update

A) Does anyone know if there is an industry wide harmony of what
different colour wires do on car alarms?

As far as I know there's not, if you think about it, it would be rather silly to do so? - it would let all the crooks know what colour wires they need to cut to disable the alarm!.

B) I have decided to take the dashboard flasher as an signal to the PIC, when the alarm is active, any different approaches?

There may be a wire which goes permanently high?, the alarm instructions should tell you?. Presuming the alarm flashes the lights or indicators when you arm and disarm?, you could use those to turn the PIC ON and OFF.

C The problem is the signal on this wire is a continous pulse, how can I convert this into a flatline DC signal to indicate to the PIC that the alarm is active?

Your PIC just needs to check for the pulsating level - basically a timed loop, if the wire is low for longer than the maximum period, then you know it's inactive. Or, if you wanted a simple DC level, use a 555 timer in "missing pulse detector mode" - this will give you a DC level.