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Timed Circuit

  1. Aug 17, 2012 #1

    First I'd like to say that I'm a complete noob so please excuse my ignorance.

    What I'm trying to achieve is essentially a switch that opens after a certain time. In my circuit, I want to have three of these "switches", the first switch set to open after 5 mins of a button press, the second switch 5 minutes after the first switch, and a third switch 5 mins after the second switch. To achieve this I was thinking that, at the initial button press, the "timer" for each switch would be set to 5 mins, 10 mins, and 15 mins respectively. At the push of another button, the "switches" would be reset to "listen" for the push of the start button (the first button press).

    My question is what can do I use for this "switch"?

    http://syntaxdonors.org/circuit.PNG [Broken]

    Here is a really simple diagram to help illustrate what I want (Sorry for the weird symbols). The empty rectangles represent the "switch", ideally they would be programmable so that the times can be changed. The dotted square with the triangle (similar to play symbol) is the push button that initiates the timers. The dotted square with the circle is the reset push button, the button that resets the timer. the rectangle with the zigzag lines represents a load, in this case and electric lock (fail-safe). When the time is up, the switch opens causing the electric lock to open.

    Again sorry for my lack of knowledge. Thanks
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Aug 17, 2012 #2


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    Staff: Mentor

    One of the simplest and most flexible ways to do this would be with a small microcontroller like a PIC:


    You would write a simple program to sense the switches, do the timings, and drive the relays. Do you have any programming experience? The PICs can generally be programmed in simple BASIC or C languages...
    Last edited by a moderator: May 6, 2017
  4. Aug 17, 2012 #3
    Ya I have lots of experience with Java and learning how to program the chip shouldn't be a problem. Would you mind detailed the circuitry of this implementation? (would I need any capacitors and resistors, etc)

    The locks I plan to use are fairly similar to these: http://www.sdcsecurity.com/docs/DBDocs/MicroCabinetLock_Datasheet.pdf [Broken]

    Thanks a lot.
    Last edited by a moderator: May 6, 2017
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