Polarity reversing switch

Discussion in 'The Projects Forum' started by yoss10, Feb 16, 2009.

  1. yoss10

    Thread Starter New Member

    Jan 21, 2009
    3
    0
    What I need looks identical to a thread I saw in this forum back in 2006. I've copied the description from hhoncho, and added few words of my own:

    I am looking for a circuit which operates a solenoid using a touch sensitive switch. The solenoid is of the magnetically latching type which functions in two directions.

    The operation should be as follows:
    The touch sensor is tripped, activating the solenoid in one direction and power is maintained to the solenoid as long as the touch sensor detects contact.

    The touch sensor is released, activating the solenoid in the opposite direction for a short time (few ms) and power to the solenoid is subsequently removed.

    The circuit must operate on batteries; I think something between 9-12 Volts. Power consumption when inactive must be kept to an absolute minimum.

    The circuit needs to be Reliable, compact and with zero/minimal delay time.
    I hope what I'm looking for is feasible...

    I have virtually no knowledge of electronics (I'm an HVAC engineer).
    I would like to understand, as much as possible for a dummy, the circuit's components, and whether there is more than one alternative, to achieve the desired solenoid's output in reaction to of the touch sensor's position.


    Any suggestions which you feel may help would be greatly appreciated.



    Thanks in advance.:)

    Yoss10
     
  2. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    For starters, You need a spring returned solenoide - that will take care of moving it to rest position when power is released.

    Then you'll need a touch circuit for energizing it while touching of course, but what specs need it have?
    Would it be OK to touch a metal sense plate, or should it be part of a plastic panel, with the touch detector hidden behind it?
    How large would the touch plate need to be?
    Anything else you might think of?
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Do you have a link to the spec's for this?

    Ken
     
  4. yoss10

    Thread Starter New Member

    Jan 21, 2009
    3
    0
    Hi,

    From what I gathered, and it's not much so far, it has to be a solenoid of a latching type. I didn't know that there are spring returned type?! I'm not sure it's what I need since it will consume current while not energized?!
    Regarding the plate: it can be metal. The point is that it has to be attached to a large steel surface. The idea is that every human touch of this surface will activate the solenoid.

    Thanks for your help
    Regards,

    Yossi
     
  5. yoss10

    Thread Starter New Member

    Jan 21, 2009
    3
    0
    Hi Ken,

    I'm not sure I understand what you mean. From what I learned about latching solenoids, when power is applied to the solenoid, the plunger moves to its energized position. The plunger latches magnetically in this position and remains there, consuming no power, until a negative electrical pulse is applied to allow the plunger to unlatch.
    I need a push force of around 10 Newtons, and a stroke of 0.2-0.3 inch

    Thanks much for your help

    Regards, Yossi
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    yoss10,

    I would first try to find the "latching solenoid" in the real world that will work for you. It's almost impossible to design circuits around speculated specifications. So if you can provide a link to its specifications.

    There many circuits on the net for touch switches. Google: touch switch circuit

    Ken
     
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