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Timer Circut Help


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Ok, Cause I am new to this I am going to act like I know what is going on... ::)

What I am trying to do is to find a timer circuit that will go for about 7 to 10 seconds and then turn on a relay and not release the relay unless either a reset manually or power loss. I have searched the web and found some circuits that will turn on a relay, but then it will shut down / release the relay after a few seconds / minutes.

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try

http://www.electronics-lab.com/projects/oscillators_timers/007/index.html

I'm not sure about this, but since it turns off the lamp it can be uset to turn it on.

or eaven better, wich should fullfill your request

http://www.electronics-lab.com/projects/oscillators_timers/013/index.html

simply adjust change he transistor behaviour. I meen instead of Q2 being turned on with Q1 make it not to be. Can't realy put the corect circuit since I only know what cam be done. Not how :P

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Find yourself a good tutorial on the NE 55 timer chip on the Net (there's a few good ones around). Basically, the 555 chip in its 'monostable' mode has what you are looking for. Pin 2, held to +ve rail via a 4.7k resistor, is switched momentarily to ground to turn the timer on. Then pin 4, which is held to ground by a 4.7k resistor is used to turn the timer off manually (use two momentary on push button switches for this task) but will time out all by itself, according to the R/C combination connected between +ve rail (resistor) and pins 6 & 7 and then from those same two pins to ground (capacitor). A good tutorial will show several wired up versions, including this one, and may even show a table of correct R/C combinations, to get close to the time out that you want, without all those messy calculations.

Alpha

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