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Latching Switching Time Delay

Discussion in 'General Electronics Discussion' started by Donwan, Feb 28, 2013.

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  1. Donwan

    Donwan

    8
    0
    Feb 28, 2013
    Hi Guys

    Lookin to build a circuit to switch a solenoid.
    Needs to have safety with it so looking to have two buttons and an LED
    Press and release button A (LED powers up for x seconds)
    If button B pressed before x times out then solenoid will open
    If button B is not pressed before x times out the LED powers down and solenoid does not open

    Any ideas on this greatly appreciated :)
     
  2. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    In case of B pressed during the LED time, activating the solenoid:
    How is the solenoid de-activated? Simply by stop pressing B, or is there a latching function keeping it on after B no longer is pressed? If latched, how do you switch it off?
     
    Last edited: Mar 1, 2013
  3. Donwan

    Donwan

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    Feb 28, 2013
    Not fully sure how to have the buttons latching with time allowance between pressing of buttons.

    The reason for the two buttons is for safety factor

    The LED is de-activated by simply stop pressing B
     
  4. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    I mean, how do you release the solenoid after it has been activated by B? Should it go back to its normal state at the same time as button is released?
     
  5. Donwan

    Donwan

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    Feb 28, 2013
    Yes it should return to normal state after button release
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    What DC power rails are available?

    Edit: Also, is it OK if holding button A down continuously causes the LED to stay on continuously? The timeout timer would start from when button A is released. Assuming the operator has to stop pressing button A in order to press button B, this behaviour should be safe, correct?
     
    Last edited: Mar 1, 2013
  7. Donwan

    Donwan

    8
    0
    Feb 28, 2013
    Not 100% sure, not from electronics background
    12V solenoid?
    Please explain

    Yes to both questions
    Holding button A LED will stay on continuous
    Timeout timer would only start when button A released, before button B can be pressed
     
    Last edited: Mar 1, 2013
  8. Donwan

    Donwan

    8
    0
    Feb 28, 2013
    Yes to both questions
    Holding button A LED will stay on continuous
    Timeout timer would only start when button A released, before button B can be pressed
     
  9. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Your idea is interesting and can be applied to many other security applications where dangerous sequences might be manually controlled.

    Here is an example of that security circuit that you described.
    I did not test it, so there could be some hidden bugs...

    The whole circuit is built around one single, low-cost IC: CD40106.
    The dimensioning of some components needs to be done, but should be an easy task.

    I don't know what power source you have for the solenoid? If you have an AC solenoid, you would need a few more diodes to switch it.

    The lowest circuit around IC1F (flashing LED) was just added because I had one gate left in the package.

    [​IMG]
     
  10. Donwan

    Donwan

    8
    0
    Feb 28, 2013
    Thanks for the Help

    Have to order in a few parts and try build this up

    Will let you know how it works out
     
  11. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Without calculating or knowing your time and Power voltage, I would start testing with these values:
    R1: 4.7M
    R2,R4,R5,R6,R7: 10k
    R3,R9: 2.2k
    R8: 2.2M
    C1: 1uF
    C2,C3,C4: 100nF
    T1 and D6 must be adapted to load and voltage. Assumed DC supply.
    I made a small improvement of the circuit diagram (R4 moved to a better place).

    [​IMG]
     
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