Help required interfacing with an existing switch.

Discussion in 'General Electronics Chat' started by Gump, Nov 23, 2011.

  1. Gump

    Thread Starter Member

    Jun 7, 2010
    57
    1
    Hello everybody,

    I've got a small music player that has got a small switch, the switch can either be on or off. At the moment, the switch is a little small, and in an inconvenient place. I think I'm rightly reluctant to try and set a small motor going just to flick it either way, not to mention that would probably be a little overkill.

    I've uploaded the couple of pictures which have turned out the best (sorry, the second one is slightly blurry). As you can hopefully see, it seems to be a small SMD thing, but I'm wondering if I try and desolder it, I could easily end up damaging the device as it is so small. So, any tips on working with such a small device and what do you recommend would be the best way to activate and deactivate the circuit it when I get the physical switch off? It's running from a very small lithium ion battery (rated 110mAh - yes 110), so later on I might also see about getting something with a bit more juice.

    Thanks very much.

    By the way, I shall be AFK for the next 2 - 3 hours.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I'm betting that the pads on either end are simply for mechanical strength and not for electrical contact with the board.

    As far as the switch terminals - you're going to have to use a meter to find out what the difference is from the two pins close together on the left are (they are connected by the visible trace), and what the single pin on the right is connected to. It's not obvious from the photo. Sad to say, the 2nd photo is so blurry that it is useless.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Just go at it with the soldering iron. Do it quick and be done. Sometimes I find its best to destroy it and just cut away what you can with wire cutters just leaving the pins mounted to the pads.. Then its easy to desolder those singulated pins.

    The 4 outer pads at each corner are just for keeping it mechanical secure. The 3 pins out the back are part of the switch circuit.
     
  4. Gump

    Thread Starter Member

    Jun 7, 2010
    57
    1
    Hi SgtWookie, Mcgyvr,

    Sorry for not getting back to you yesterday... Seems I'm paying my ISP out of the goodness of my heart and a reliable connection doesn't seem part of the agreement... Anyways, thought I'd at least reply to let you know how things went.

    Yes, the four pads on the corners were just there for mechanical strength, I can't say I've taken many things apart - or rather haven't looked at them closely, but is it standard to fix SMDs to the PCB using soldering? I'd have though they would have used some sort of adhesive.

    Using just some thin needle wire cutter things I managed to get the switch casing off and once opened is pretty obvious what things do. I've included a basic diagram (photos don't seem to go well), but it's really just the three contacts.

    To be honest, after seeing the size of the contacts, I'm considering shorting the switch closed and instead inserting perhaps a suitable SSR between and a new battery cell with some more power.

    Thanks,
    Gump.
     
    Last edited: Nov 25, 2011
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