Connecting car alarm to light circuitry

Thread Starter

Georacer

Joined Nov 25, 2009
5,182
A friend of mine has bought this car alarm system:
http://www.clifford.com/Products/Product.aspx?ProductID=721

He wants to connect the auxiliary output of the alarm to the lights, in order for them to flash I guess.

The problem is that the AUX output is only 0.5V high (It's not written on the site, but I believe him). How can I control a 12V voltage with only 0.5 volts?

He thought of a relay at first, but I don't think that there's a relay that switches on with only half a volt.

My thougt is to use a transistor to activate the relay, or a power transistor to replace the relay altogether. However, I don't have any schematics in mind.

Any thoughts or recommendations?
 

tom66

Joined May 9, 2009
2,595
Modifying the lights could be dangerous. Imagine if your relay tries to turn the lights on and off while driving due to a short on your board. It could be bad.

However, you could probably use a comparator to detect the 0.5V signal and drive a transistor/relay combination with the comparator output. A bit of a long winded way to do it, but it might work.
 

Thread Starter

Georacer

Joined Nov 25, 2009
5,182
I don't think we run a risk of the lights turning off. The controlled relay will be connected in parallel with the light switch. If the latter is on, it stays on.

That was a good one.
Anyone else?
 

Thread Starter

Georacer

Joined Nov 25, 2009
5,182
I just realised that this thread is off forum rules.

I ask for a moderator to delete it at their own discretion.
 

beenthere

Joined Apr 20, 2004
15,819
Given the intent of an alarm function and the headlamp relay being able to override, the flasher, it sounds like an acceptable topic.
 

Kermit2

Joined Feb 5, 2010
4,162
Reading up on the product, I don't think it is a 'relay' type output. I believe it is a PWM coded output port for one their 'patented' add on modules.
 
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