2x 555's for on + off delay

Discussion in 'The Projects Forum' started by bert77, Nov 14, 2014.

  1. bert77

    Thread Starter New Member

    Nov 14, 2014
    5
    0
    hi forum,
    i'm trying to design a simple circuit for solenoid ctrl. to make a brief description of circuit function:-
    switch sends 12v to 2 solenoids. (call them solenoid a, solenoid b)

    after switch on, sol-a powers immediately, sol-b powers after a few seconds delay.

    when switch off, sol-b powers off immediately, and sol-a powers off after a few seconds delay.
    i was hoping to find easy way without arduino/pi and any help on doing this with 555's appreciated.
     
  2. Ramussons

    Active Member

    May 3, 2013
    557
    92
    Use a 555 as a Delay.
    upload_2014-11-15_11-58-55.png


    The Relay operation will follow the input based on RC time constant delay. (sorry, too lazy right now to give the calculations ;):(
     
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    The timing diagram as below:

    2x 555 for on + off delay_bert77.gif
     
  4. bert77

    Thread Starter New Member

    Nov 14, 2014
    5
    0
    thanks guys, that was super info.
    a bit more info:-
    the sols draw 0.5 amps at 12v and it would be nice to know if the controlling operation can also be achieved without the ne555's, as this would save money....
    just using diodes caps and pots.

    being able to adjust the delays in the 0-2 second range with 2 pots would be ideal.

    the system is actually for a portable welder controlling gas and wirefeed, so the 2ah batteries (one for each solenoid) will be running down fron 12.6 to 11v in field use.

    would the running down of the supply voltages affect the 'absolute timing' in any non ne555 setup, or is digital controll mandatory for precision??

    many thanks
    bert.
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,853
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    How do you match when the switch on then the sol-a will be on? (no delay)
    How do you match when the switch off then the sol-b will be off? (no delay)
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Here is my circuit to do this. M1 and M2 are (almost) any TO220 NFETs. They drive 12Vdc 1/2A Solenoids LA and LB directly.

    In the simulation, the switch closes at 2sec and opens at 10sec {V(sw12v), Green trace}. Coil A {I(la), Red Trace} turns on immediately, and turns off about 2sec after the switch is released. The hold time of coil A is proportional to the product R1*C1.

    Coil B {I(Lb), Blue trace} delays turning on by about 2sec, and turns off as the switch is released. The turn-on delay time of coil B is proportional to the product R2*C2.

    The gate voltages of the NFETS are constrained to be less than 10V by the voltage divider R3, R4. The steering diodes D2 and D4 reset the timing networks quickly for a new cycle. Diodes D1 and D3 are snubbers for the relay coils.

    225.gif
     
    Last edited: Nov 16, 2014
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    Go to check the timing diagram I drawn on 3#.
    And to see the circuit from MikeML on 9#.

    I drawn the timing diagram from what the TS described, you can using your own method to design and match the timing diagram.
     
  8. bert77

    Thread Starter New Member

    Nov 14, 2014
    5
    0
    hi, i will give all circuits a try, reporting back after i get the bits and refresh breadboard layout skill.

    I counfused myself as I thought i needed to separate the motor controll (1 amp @Max speed) battery from the sol a side, (currently using 2 batts as the v drop slows the motor) which must be stable after set by pwm ctrlr dial. but as the motor is on the b circuit so its speed it always adjusted when sol-a is on, hence all ok.

    really helpful,
    best thanks to all
    b/
     
  9. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    If you go the 555 route, you will need two 555s, and three additional 12V relays. My approach avoids all the extra bits...
     
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