Simple timer to control a solenoid

Discussion in 'The Projects Forum' started by Drgogo, Nov 1, 2012.

  1. Drgogo

    Thread Starter New Member

    Nov 1, 2012
    3
    0
    OK guys I hope you can help me on a little project which sounds simple, but has been quite complicated.

    The Project

    A simple timer which controls a solenoid.

    Explanation

    I need a timer that can be triggered by a start button, then after a set amount of time like 30-40 seconds, the circuit then triggers a solenoid for 5 seconds, then resets.
    There is also a stop/reset button to stop the sequence if needed.

    Also when the start button is pressed a buzzer and flashing LED would be activated, but these need to stop if the stop/reset button is pushed.

    Oh and it needs to run off a 9v battery

    Sounds simple......

    Now I've looked on the web and have found plenty of diagrams and ideas using a 555 timer, some are adjustable, some are not. I have also seen some you tube videos, I can also buy one, but it needs 12V, which is not practicable.

    I did find one circuit that may of helped, but I dont know is it would power the solenoid.

    So I hope someone can help, the last time I done electronics was about 23 years ago when i was a school/college and never really followed it through.

    I know its a big ask, but even a push in the right direction or a curcuit diagram and a list of parts would help, and I can then sort out the rest... Some how lol

    Look forward to hearing some replys.

    G
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    Will the 9V battery be able to activate your solenoid?

    And yes, a 555 timer circuit should do the job for you. You might need a 556 dual timer to control the delay and then the on time.
     
  3. Drgogo

    Thread Starter New Member

    Nov 1, 2012
    3
    0
    Well I can get hold of a 4.5v Solenoid, but One video I have seen (The only one on you tube showing a 555 timer) is using a 9 v battery and a 12 vdc solenoid
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    If you don't need great precision in the timing, essentially what you need is a 35 second timer with a duty cycle of about 85%. Use the output to control the base of a PNP transistor, and use the transistor to supply power to the solenoid which is grounded to battery negative. With a pull-up resistor, the transistor will be off when the timer output is high. It will turn on for the 15% of the cycle when the timer goes low. The timing sequence can be reset.

    An LED and small buzzer can be powered directly off the timer output, however that will go off when the solenoid activates. Do you really need it to flash? That requires another timer.
     
  5. Drgogo

    Thread Starter New Member

    Nov 1, 2012
    3
    0
    No the LED does not have to flash, and its fine for these to go off when the solenoid is activated, these are only a warning while the timer is active.

    I would say that what you have written sounds great, but unfortunately, my electronic knowledge is rather limited, I know enuff to burn my fingers when soldering lol

    Would the circuit incorporate a reset/stop button ?
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    Read about the 555 and the function of its reset pin. I think it'll be what you want but I've never used it myself. And yes, if it sounds like what you need, you'll just put a switch in between it and either V- or V+, whatever the datasheet says.

    BTW, you should get a breadboard and play around with this a bit before you actually solder and build. If you've never used a breadboard, you'll love it and wonder why you didn't get one sooner.
     
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