Trigger relay using 3V

[letsrelaythat]

Hi All,

I have recently installed a car alarm, and I previously had an LED setup which ran from 12v. I use a luxeon star module LED, which needs 4.8 volts to run at max.. So I have a 27Ohm 5W resistor, which, when hooked to the cigarette lighter terminal, produces a very nice light. The problem I have, is that the alarm puts out pulses of 3v. I need to either increase this 3v to 12v, or use another 12v and switch it by a relay.

I have looked into my local electronics store, but I could only find a solid state relay that would switch at 3v. I'm really after a cheaper alternative, I thought about some sort of transistor amplifier but I wasn't really sure.

If anyone can provide some sort of assistance or diagram that would be very helpful.

Thanks in advance,

Tim.

 

[VISHOK]

hello,
I went through your problem.U can switch a simple switching transistor.u have to wire 3v signal to a transistor BASE through a proper voltage divider circuit which can reduce 3v to 0.5volts.with this 0.5v transistor will conduct.Wire the coil of relay to the COLLECTOR of the transistor and hold the EMITTER of the transistor to GROUND/-vcc of your cicuit.Then u can use the contacts of relay to move any voltage further.

 

[ljcox]

As I understand your question, you only want to turn the LED on when the 3 Volt pulse is on. If this is correct, then all you need is a resistor and a NPN transistor. (you don't need a relay)

Connect the emitter to gnd, the resistor from the base to the 3 V pulse and the collector to the LED with the 270 Ohm resittor in series to the 12 Volt supply.

I assume that both the 12 Volt and 3 Volt are positive with respect to ground.

Len

 

[fahim]

Hi All,

I have recently installed a car alarm, and I previously had an LED setup which ran from 12v. I use a luxeon star module LED, which needs 4.8 volts to run at max.. So I have a 27Ohm 5W resistor, which, when hooked to the cigarette lighter terminal, produces a very nice light. The problem I have, is that the alarm puts out pulses of 3v. I need to either increase this 3v to 12v, or use another 12v and switch it by a relay.

I have looked into my local electronics store, but I could only find a solid state relay that would switch at 3v. I'm really after a cheaper alternative, I thought about some sort of transistor amplifier but I wasn't really sure.

If anyone can provide some sort of assistance or diagram that would be very helpful.

Thanks in advance,

Tim.