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i need help in a timer delay circuit

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shahabmusic

New Member
hi,

I have a motorized LCD in my car and when I turf off the engine it goes inside but when ignition switch is on, it wont turn on and I have to push the EXIT button to turn on lcd and open it.

LCD front panel uses resistive technology for buttons I guess. because when I add some cables to the exit button to take it few meters away, it does not work.

I am currently simulating EXIT button pressing by using a relay, resistor and a capacitor; i made a circuit that when my 12v line is available, relay contacts turn to close for 1sec and then turn back to open position. this solution is no longer work for me, i would go for a digital one to learn little bit more about electronic and solve this problem.

I found that there is a component called optocoupler that does exactly same job as relay but it's much faster and more accurate... and I found an IC called 555timer. I'm guessing that there would be some ways to make the circuit that I am looking for by using this two components but have no clue how:-(

I would greatly appreciate any sort of help
Shahab:)
 

mramos1

Active Member
google 555, or 555 relay circuits. It is a very popular chip for people starting in electronics. You might find exactly what you are looking for.

Why did the RC circuit stop workinCan google on-shot and mono-stable as wellg? Maybe you need to change a value and stretch the pulse out a little longer?

Can google one-shot and mono-stable 555 as well
 
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shahabmusic

New Member
thanks a lot. i found some but still have heaps of problems:(
why RC circuit stopped working? you know car stereo has 3 power cables. 12v battery(on all the time), ACC cable(ignition) and negative. and also my RC circuit is on the ACC rail.
what I have just changed is that I have connected the LCD battery cable to ACC, so power is available to both battery and ACC cables as well as my RC circuit exactly at same time. so when the relay operates and simulate the EXIT button, is when that car LCD is not fully operational because it has just got power to its 12v rail.... so I have to add a delay to RC circuit.
I put the relay in dash behind the LCD and when its operates, its contacts make annoying noise so that's why i have started to think about something digital and more smooth :)
 
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