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activate one coil in press, and the other in second press

Discussion in 'Power Electronics' started by ostr1969, Dec 7, 2018.

  1. ostr1969

    ostr1969

    6
    0
    Dec 5, 2018
    i have 555 timer
    i need an analog circuit that activate 9V solenoid with 2 coils and one button in this way:
    press - 1st coil on
    release - 1st coil is off
    press - 2nd coil on
    release - 2nd coil is off
    can it be done with the 555timer?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    8,790
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    Nov 17, 2011
    Would be awkward.
    A T-flipflop + 2 AND gates would be easier:
    upload_2018-12-7_12-36-7.png
    The RC combination to the left is a primitive debouncer for the button S1.
    The flip flop is configured as a togggle flip flop. with every press of the button S1 the outputs Q and /Q (can't mark the Q with a dash on top here) toggle states and are inverse.
    The AND gates evaluate the flip flop's outputs and the state of the button to activate a coil only while the button is pressed.
    The resistor and transistor are a power stage for driving the coil. You'll need two of these as indicated by the dashed line.
    The flyback diode across the coil protects the transistor from overvoltages when turning off.

    A CD4013B is a suitable flip flop chip. Remember to tie the set and reset pins to ground. Also tie all inputs of the unused second flip flop in the package to gnd to prevent unpredictable behavior.
     
    Last edited: Dec 7, 2018
    hevans1944 and CircuitMaster like this.
  3. CircuitMaster

    CircuitMaster

    48
    1
    Dec 17, 2016
    I agree. This is a good option.

    Can you explain a little more please?
    You have used the switch to activate the coil on the second press, won't that mean the "T flip flop" has to be activated on the rising front?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    8,790
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    Nov 17, 2011
    Yes it does.

    Each press activates alternatingly one coil or the other.
    I haven't shown the second coil, see my note in post #2
     
  5. hevans1944

    hevans1944 Hop - AC8NS

    3,942
    1,879
    Jun 21, 2012
    Read the datasheet for the D-type flip-flop that was suggested. The flip-flop changes states on each rising edge of the clock input, i.e., each time the switch is pressed. It is the connection of the /Q output to the D input that causes the flip-flop to change states. The AND gates steer whatever state the flip-flop happens to be in after the switch is pressed to the appropriate relay coil driver (only one is shown in Harald's schematic; the second one is implied by the dotted lines), but only while the switch is pressed. Releasing the switch will cause the flip-flop to change states the next time the switch is pressed.
     
  6. ostr1969

    ostr1969

    6
    0
    Dec 5, 2018
    Thanks i is really looks simple.
    Can U recommend also for the transistor part and the AND gates part?
     
  7. CircuitMaster

    CircuitMaster

    48
    1
    Dec 17, 2016
    I know what it does, I just haven't seen this circuit.

    The idea is that on the press, the flip-flop will not be active if its a falling front, it has to switch at the rising front so after the press while still holding the button we have 2 x "1s".

    I meant to write "falling" front in the upper post. But I now I figured out it should be rising.
     
    Last edited: Dec 7, 2018
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    8,790
    1,721
    Nov 17, 2011
    Pressing the button will create a rising clock edge.
    This is exactly what is evaluated by the AND gates to control the transistors.
    AND gates: 4081 B or use NAND gates from a 4011B where you use 2 of the four NAND gates in the ic to invert the NNAD's output for an AND as shown here.
    transistor: use on which is capable of supplying the current the coils require. The base resistor should be somewhere between 10*Rcoil to 30*Rcoil, the exact value is not critical. Note that a 4011B can supply about 1 mA output current. A 2N2222 transistor for example has a min. current gain of ~50, meaning you can drive up tp 50 mA coil current with 1 mA base current. reliably. If you need a higher collector current, consider a 2-stage transistor amplifier or using a MOSFET (see for example here for a selection table) or use a HUFA76429D3. You will not a base resistor when using such a MOSFET in this application, although limiting the gate current by a small resistor (around 10 Ω) is good practice.
    Lacking information about your coils I cannot give a more specific recommendation.
     
    hevans1944 likes this.
  9. ostr1969

    ostr1969

    6
    0
    Dec 5, 2018
    I really appreciate the detailed information. it is as gold for rookie like me. The coils are 9 ohm each and driven from 6-12V source.
    i think if means that the around 1A so all the transistor must be much bigger?
     
  10. Bluejets

    Bluejets

    3,043
    595
    Oct 5, 2014
    Last edited: Dec 9, 2018
    hevans1944 likes this.
  11. WHONOES

    WHONOES

    578
    113
    May 20, 2017
    The good old 4013 will perform that function when configured as a divide by 2.
     
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