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push-push on/off switch

Discussion in 'Electronic Design' started by John Larkin, Oct 21, 2007.

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  1. Jim Thompson

    Jim Thompson Guest

  2. Rich Grise

    Rich Grise Guest

  3. Joerg

    Joerg Guest

    No, but if someone holds the button long enough it'll be a "Phsssst -
    pop - crackle - KABLOUIE" moment.
     
  4. John Larkin

    John Larkin Guest

    It works as a dimmer, too.

    It's interesting to play with.

    John
     
  5. John Larkin

    John Larkin Guest

    Why would it oscillate? No, it's a push-push on/off switch.

    John
     
  6. Jim Thompson

    Jim Thompson Guest

    <Smirk>

    ...Jim Thompson
     
  7. Jim Thompson

    Jim Thompson Guest

    Bwahahahahaha!

    ...Jim Thompson
     
  8. John Fields

    John Fields Guest

    ---
    Not according to LTSPICE:

    Version 4
    SHEET 1 880 680
    WIRE 208 -352 -272 -352
    WIRE 208 -288 208 -352
    WIRE -272 -176 -272 -352
    WIRE 0 -176 -32 -176
    WIRE 208 -176 208 -208
    WIRE 208 -176 80 -176
    WIRE 208 -112 208 -176
    WIRE -32 -32 -32 -176
    WIRE 32 -32 -32 -32
    WIRE 160 -32 112 -32
    WIRE 48 16 -176 16
    WIRE -176 48 -176 16
    WIRE -32 64 -32 -32
    WIRE -272 160 -272 -96
    WIRE -176 160 -176 128
    WIRE -176 160 -272 160
    WIRE -32 160 -32 128
    WIRE -32 160 -176 160
    WIRE 96 160 96 16
    WIRE 96 160 -32 160
    WIRE 208 160 208 -16
    WIRE 208 160 96 160
    WIRE -272 208 -272 160
    FLAG -272 208 0
    SYMBOL nmos 160 -112 R0
    SYMATTR InstName M1
    SYMATTR Value FDC637AN
    SYMBOL res 192 -304 R0
    SYMATTR InstName R1
    SYMATTR Value 12
    SYMBOL res 96 -192 R90
    WINDOW 0 0 56 VBottom 0
    WINDOW 3 32 56 VTop 0
    SYMATTR InstName R2
    SYMATTR Value 1000
    SYMBOL cap -48 64 R0
    SYMATTR InstName C1
    SYMATTR Value 1e-7
    SYMBOL voltage -272 -192 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 12
    SYMBOL voltage -176 32 R0
    WINDOW 0 -53 5 Left 0
    WINDOW 3 -242 110 Invisible 0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value PULSE(0 1 2 1E-6 1E-6 1 2)
    SYMBOL sw 128 -32 M270
    WINDOW 0 32 15 Left 0
    WINDOW 3 32 44 Left 0
    SYMATTR InstName S1
    TEXT -184 232 Left 0 !.model SW SW(Ron=1 Roff=10Meg Vt=0.5Vh=0)
    TEXT -184 200 Left 0 !.tran 10


    Or maybe I picked the wrong parts. Got some values that work?
     
  9. John Larkin

    John Larkin Guest


    My sincere apologies to LTSPICE, but it does work.

    Try, say, 1M and 0.47 uF.


    John
     
  10. Jim Thompson

    Jim Thompson Guest

    Yep, It will work for optimal button-press times. Then it will leak
    one way or 'nother ;-)

    It's fun that it works, but otherwise useless.

    ...Jim Thompson
     
  11. John Larkin

    John Larkin Guest


    Does everything that's fun have to be useful?

    John
     
  12. John Fields

    John Fields Guest

    ---
    Tried it, it didn't work, and what about that floating gate when the
    switch opens? (Yuck...)

    Or maybe I'm misinterpreting your drawing.

    I see a normally-open momentary switch, an N-channel enhancement
    mode MOSFET, and an R and a C.

    Am I missing something?
     
  13. Jim Thompson

    Jim Thompson Guest

    No. But a stable-state switch would be more interesting.

    ...Jim Thompson
     
  14. Fry when it eventually drifts into the linear region?



    Best regards,
    Spehro Pefhany
     
  15. Winfield

    Winfield Guest

    Your sketch, for the permanent record,

    ,---/\/\----+----o LOAD o-- +V
    | |
    | |--'
    | ___ ||<-,
    +--o o--||--+
    _|_ |
    --- gnd
    |
    gnd

    A 0.5-s time constant. Should work with most
    modest pushbutton presses. My experiments show
    modern power MOSFETs can hold their gate voltage
    for days, if not weeks. But surely you remember
    out long-running thread that completed the simple
    circuit with a 2nd transistor making a flip flop.
     
  16. Jim Thompson

    Jim Thompson Guest

    The problem is that there is NO stable state to start from. A true
    F-F is the only way to go.

    ...Jim Thompson
     
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