Tracker & Alarm Door triggers

[TheWolfman]

So here’s the rub...

I’m installing a separate tracker and alarm in a friends vehicle,both of which have inputs for negative door triggers.

My question is will diodes be required in order for both units to function correctly if connected to the same door trigger?

Thoughts and opinions appreciated as ever.

[reelizmpro]

It could very well work fine but you should always diode isolate when tying in two systems to the same trigger. Do it once, do it right.

[slum dog]

I have a project e30 with shaved door and boot locks.
I installed an aftermarket alarm system with keyless entry system, when I spoke to the alarm guy my supplier, he recommended the negative trigger system because I could use the dome light switches as Secondary Triggers cause it's also a negative switch. Diodes was supplied but I never use them.

[TheWolfman]

Thanks for the replies guys...I forgot to subscribe to thread so only just seen them!

I’m just trying to figure out now which way the diodes should actually go...I’m thinking the diodes need to feed this way around:

Door Trigger ———— >| ———— Tracker
Door Trigger ————->| ———— Alarm

Does that make sense??:)

[reelizmpro]

The bands go on the door switch side.

[TheWolfman]

Thanks for the info reelizmpro.

Just wondering if you could possibly explain a little further as to why this is the case for my understanding?it does indeed make sense that the units only see ground when the door is closed and thus current can flow ‘towards’ the doorswitches ground.

My thinking was that the units needed to see the initial 12v positive voltage flowing from the door switch to the units...this is probably me being stupid!

[reelizmpro]

The current will flow from the closed switch to the tracker or alarm from cathode to anode but block any current going the other way which could interfere with the other unit when the switch is not closed. One diode will isolate the tracker and the other will isolate the alarm. The diagrams will explain it better.




In your case, the 2nd diagram will be slightly different. Not sure how critical it is with your tracker/alarm units but alarm sensors will falsely activate without diode isolation if there is more than 1 on the same trigger.

[TheWolfman]

Thanks again for the detailed and concise info reelizm,very much appreciated...totally makes sense that way around when I think about it now.Time to get to it!

[slum dog]

Great info reeliz I am also gona revisit my setup.