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Homework Help: 555 circuit to open and close curtains

  1. Jun 20, 2014 #1
    1. The problem statement, all variables and given/known data

    I want to make a 555 circuit open and close some curtains. It has to open them at 6am and close them at 10pm

    2. Relevant equations


    3. The attempt at a solution

    555 circuits are not very accurate for long periods of time, so the solution is to use a plug in wall style timer that activates at 5:45am and again at 9:45pm.

    When the wall timer activates the circuit is initialised it is a monostable circuit so it will turn on the motor for a few seconds, this can be varied with varying capacitors and resistors.

    The only problem is how to close the curtains as the next signal needs to be the reverse voltage ie - instead of + I'm not sure how to do this part.
  2. jcsd
  3. Jun 20, 2014 #2


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    2017 Award

    Staff: Mentor

    Options I see:
    - include some memory that can hold its value for a day
    - include a sensor to detect the current curtain status
    - power it from 6 am to 10 pm, so you can use "power off" as a signal, store enough energy in capacitors to close the curtains
    - power it in some other scheme in such a way that the circuit can distinguish between those cases

    Reversing outputs is not so hard if you have some way to find out when to do that.
  4. Jun 21, 2014 #3


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    Staff: Mentor

    You could position a small phototransistor to focus on some part of the timer readout to detect whether its reflectance corresponds to that measured when the character displayed is for AM, otherwise it's PM.
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