Latching timer

Discussion in 'Circuits' started by ryanh1008, Feb 1, 2014.

  1. ryanh1008

    ryanh1008 New Member

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    Hi I'm Ryan and new here. I'm looking for some help with a circuit I want to design.

    Basically I will have a signal from a solenoid that will only be there when the solenoid switches. So from this signal that will last less than a second I want a timer circuit to be triggered and count 10 seconds to light a bulb and then reset. I know this should be a simple circuit but I just can't think.

    Can anyone help?
  2. Justin

    Justin Member

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    Welcome to the forums Ryan! I personally am not good with designing circuits, but somebody here may be able to help you.
  3. George

    George Moderator

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    Here is a quick simple one. I am adding a video of it operating below this post as well. Here is a screen shot. I or someone here can give more details later. I wont be on again until later tonight or tomorrow. I don't know what voltages you are dealing with so I just used 5v for trigger and 12v for supply. You will also need a resistor for the LED that I forgot to add in as I am in a hurry. User named Fleck made this circuit but with more components, I just pulled out this part of it to get you started. Please say thank you to Fleck.


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    Last edited: Feb 1, 2014
  4. George

    George Moderator

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  5. cstmwrks

    cstmwrks New Member

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    I have a 555 timer circuit I've been tinkering with off and on but have yet to get one that works right. Or at all. The project is based off an LM3914 bar graph driver chip. Power to the circuit is 9v, one of the LED outputs on the 3914 would be selected to trigger a function through a relay.

    So lets say pin 14 goes high on the 3914, this high signal needs to be able to send a 1 second signal to a power relay. After that one of two things may happen.
    1 - the signal from pin 14 goes away as now pin 13 is driving a LED, no more 1 second signal is needed to the power relay. OR
    2 - the signal from pin 14 does NOT go away, 15 seconds later another 1 second signal is sent to the power relay.

    So basically if things work right, when pin 14 goes high a 1 second signal drives a power relay to the device that solves the issue with 1 second of action.
    If not, then as long as pin 14 is high there will be a 15 second pause between 1 second triggering of the relay. And so it will go, 1 sec on, 15 sec pause so long as pin 14 is high.

    I've been told that to do this "right" I would need an oscillating 555 timer to do the 15 second pause and a one shot timer to do the 1 second triggering of the relay.

    Does this sound right? or is it possible to have a single 555 be triggered from the high signal from the LED driver output to turn on a power relay and then either pause for 15 seconds and trigger again, or stop altogether with the loss of signal.