so i have kinda a no name car alarm but it works and hteres no reason to replace it just yet.....but i want some sort of battery backup so someone cant just pull my battery cable and disable my whoel system...so is there anything i can make myself to achieve the same effect ?

 

nothin?

 

a sh**load of capacitors would work...heh....j/p...they sell back-up battery things...dont knoe if they really work like they suppose too...

 

It would seem cheaper to just buy one. They cost about the same as the battery by itself.

But yes you could build one.

Something really simple

1) Diode going from charge side to + terminal of backup battery.
2) Diode going from - terminal of backup battery to ground.
3)Diode going from + charge side to resistor, then resistor to - terminal of backup battery.

The point at which the diode and resistor meet would be you - trigger to your alarm. This would trigger the alarm if the battery was disconnected.

resistor value should be approx 25k ohms.

Shottky diodes would be ideal.



Modified by nsxxtreme at 11:03 PM 8/5/2005