auto on switch

[acrbill]

**broken link removed**
*edited*

First off is all of the grounds. Am I supposed to tie all the grounds together and ground them to the chassis of the car? To the ground wire on the harness? Also I see the symbol for a diode. I looked up what a diode is and there seems to be a few different types. Which one am I looking for? Also why do I need a relay? Or is that output going to connect the the wire on the harness for the switch?

Also I would like to delay to last 3 seconds. What would I need to change to acheive that?

thanks

 

[acrbill]

hrmm... I just saw a 556 timer that is 2 555 timers in one unit. anyone know where I might find a schematic for a "one shot" 556 circuit??

 

[acrbill]

I was doing some testing and found out I dont need a time delay. So instead of doing the dual 555's I did one instead. I found this **broken link removed** (I ommited the 220uf cap)

My first problem was the the 555 I got from radio shack wasn't labeled at all.
I had no idea if I have the switch soldered in correctly. Since I am using the ignition as the trigger I ommited the trigger switch off pin 2 and went directly to ground. When I tested the circuit out it kept the test light lit. I realized I had shorted the circuit for the #2 pin. so I snipped the wire going from #2 to ground and the light went out. I figured if I jumped the wire for a moment like a switch it would work. the light only stayed lit when the jumper was in place.

If anyone understands what I just wrote and can help me, let me know.

thanks

 

[acrbill]

Well I finally got my project working. I ditched the 555 timer and simply used a relay. I am having one small issue though. I tapped into the start wire for the relays trigger. So when I twist the key to start it activates the relay which essentially jumps the wires going to the switch. The problem is that I need to hold the key in the start position a fraction of a second longer so the wire providing the constant voltage is re-energized after the power is sucked away to start the car. Im not 100% sure on how a capacitor works so if im off base let me know. I was thinking of installing a resistor/capacitor inline with the trigger wire so that when I release the key the cap will have some juice to trigger the relay. Will that work?

Thanks

 

[gerty]

That is why I reccommended putting a 1,000uf capacitor on the relay, it'll hold the relay in for a few seconds. Just connect it across the relay coil,so that when the relay is energized so is the cap. The cap will store the charge when the key is turned and hold the relay in untill discharged...

 

[acrbill]

sweetness!

thanks a lot man

 

[kybert]

if the capacitor you use is a electo type, make sure you connect it the correct way round, or it'll pop and splatter you car with aliuminum dust...


eeewwww

 

[acrbill]

welp its all done. I put in a 220uf cap and 1k resistor and everything works fine now. Thanks for all your help guys!