Hi, I’m very new here, and I basically found this forum while searching for answers concerning my latest project. I’m trying to build an automotive “turbo timer.” For those of you who don’t know Commercial turbo timers consist of 3 wires; a 12v wire, a ground wire, and an ignition monitor wire. While the key is turned the ignition wire supplies 12v. When the key turned back the ignition wire goes to 0v and the turbo timer immediately routes 12v back into the ignition wire for the set amount of time. This is what I’m trying to build. I am only a sophomore electrical engineer, so all I’ve been taught so far is theory. I need someone who knows electronics (specifically the LM555 IC) to help me out. I’ve attached a schematic of my proposed circuit. In theory it should work as follows: Key is turned in vehicle and 12v goes through ignition wire, diode, relay, resistor, and then to pin 2 on LM555. When key is turned back ignition wire goes to zero making pin 2 go low and causing pin 3 to fire and power the relay, which in turn directs 12v back to the ignition wire for the amount of time dictated by R2 and C2. The diodes and C1 are there to help prevent voltage spikes. http://www.halfspec.com/sc2.GIF (Full Size) That’s it! I was hoping it would work, but right now it’s not. I’m pretty sure the timing setup dealing with pins 4,6,7, and 8 is correct, because this is pretty standard in other LM555 circuits. I appreciate any input on this, because I’ve been trying to diagnose the problem all day and haven’t been able to make any progress. Lane Simmons
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