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kidoh

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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:)hi,

to simplifiy, why dont you use an SCR to turn on the relay. once the SCR is turned on it will remain on until such time you cut off the power. all you have to do is place a timing circuit to the gate of the SCR. :)

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