imported_f4guy905

I am going to install a fuel pump kill switch on my car but want to add a little extra security and something to remind myself to turn it off. I want to run everything just like normal, but I want to set it up so when the fuel pump is switched off, a red LED light starts to flash on the dash (like a alarm). The question I have is how exacty would I set this up? I was thinking of a relay, but I'm not 100% sure if that is the right way or not. thanks.

Matt

imported_Syphon

with a dual pole dual throw switch. You wire in 2 circuits. one is the fuel switch. Then when the switch is flipped it changes to the other circuit which blinks the LED. pretty easy actually. If you need a can draw a quick diagram.



EDIT!!

Err.. my mistake.. you need a single throw dual pole switch!

and a simple sorta.. horrible diagram:



The switch is a circuit schematic sorta.. the dashedline shows it alternate position. So when you open the fuel pump, your LED assembly (relays and all) will come on. Sorry if it makes no sense.

imported_ERTW

you dont need a relay for the led.. just get a 12 volt flashing led, or a regular 3 volt flashing led and wire it in series with a resistor. your resistor should be in the range of hundreds of ohms, and the lower the resistance, the brighter the led will be.

imported_Syphon

330 ohm is the recommended rating for 12v

imported_f4guy905

That diagram does help me out, just one question though....would the LED run right back to the battery or just get grounded? Also, the LED would be on constantly, wouldn't it?

imported_Syphon

well, as ERTW said, you can get 12v flashing LED's that flash on and off. If you get a standard led.. you will need a timed relay sorta system that will make it flash. I'm sure you can get the LED's with all the stuff you need cheap.. I've seen them at future shop.. bright blue LED's that blink.. they were like 15$ and had a little relay system that allowed it to blink on and off. Pick up something like that.

imported_starboy869

check out radio shack.. they used to have cool electronic stuff

kwikb16a2

the best way is to use a reed relay i posted the writeup a while ago. Basically you use a magnet to activate the fuel

imported_loudsubz

This is how its wired

imported_loudsubz

ok basically with the schematic I drew, its utilizes a single pole single throw relay and a 555 timer to blink the LED

the parts to build a 555 timer should be like $2-3 and with a potentiometer you can control how fast the led blinks etc, if you want that.

You have a switch, and a 12v source on one side. IN off mode (Normally Closed) the relay allows the voltage to pass through the relay on one side (NC) and on the normally open side, the circuit is cut and is not allowing anything to go past.

When you hit the switch, it energizes the relay, once its energized it switches states to the Normally Open side, and now makes it Normally closed, and the normally closed side becomes normally open, opposite.

If you put 12v feed on the common, the 12v will pass through the Normally Open side now and turn on the LED, but at the same time will cut the fuel pump circuit that was on the Normally closed side.

Hope you understand