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problem with desoldered buttons

Discussion in 'General Electronics Discussion' started by beerzinnss, Apr 21, 2017.

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  1. beerzinnss

    beerzinnss

    8
    0
    Sep 26, 2016
    Hi!
    I am trying to control a bluetooth amplifier board with an arduino. The amplifier board has five buttons (vol+, vol-, next, prev, play/pause). To control them with arduino, I am going to use an optocoupler (4N35).
    I desoldered the buttons, soldered short wires to the respective pads. Now I have some problems that I don't understand, maybe you can help:
    1) vol+ and vol- work when touching the wires, BUT when i separate them, if I keep holding the wires (even by the insulation) it keeps being pressed. stops when I let go.
    2) other three buttons don't work when touching the wires, in fact the bluetooth module restarts when "play/pause" wires are connected for more than ~5secs. BUT they do work if I touch the pad directly with the other wire.

    So now I'm confused, are the wires the problem? is it worth trying other wires? (these are from an HDMI cable)
    I tried connecting the optocoupler and arduino on a breadboard, it behaves the same as when I'm touching the wires - volume buttons work, others don't, if play/pause is connected for 5-10seconds, the module restarts.
    I am an absolute beginner in electronics, so any help is appreciated.

    see attachments below. Thank you!

    bluetooth amplifier board - http://www.ebay.com/itm/TDA7492P-AU...015219?hash=item1c730868b3:g:K7AAAOSwux5YS5~W
    CSR8635 Bluetooth chip datasheet - http://electrothing.co.za/images/products/bluetooth-audio-module-8/CSR8635-datasheet.pdf
    photo of the wires on the amp - IMG_3765.JPG
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    It is possible that the long wires are acting as antennas, picking up stuff that the module assumes are button presses.

    You may be able to fix this with pull ups or pull downs, but it is hard to say which is required and on which wire without investigating the board in some detail.
     
  3. 73's de Edd

    73's de Edd

    3,121
    1,315
    Aug 21, 2015
    If my problem to solve . . . . my choice would be the totally isolated interfacing provided by a reed relay.

    Each unit would be mounted vertically in the former pad center . . . and they would stick up no more than the height exhibited by the existent GREEN Euro terminals over to the side.

    At 5 V supply only 10 ma are needed for the coil hold in .

    Evaluate to see if an inductive kickback snubber diode is also needed across the relay coils .

    Its 'a looka like 'a dis . . . . . . . . . oh . . .mamma mia

    [​IMG]
    FULL Item Referencing at :
    http://www.mouser.com/ProductDetail/Coto-Technology/9007-05-00/?qs=sGAEpiMZZMv4tz1TW/ArE/vBcES3K/TMPx9HaJD404c=


    Its Da Da Sheet :
    http://www.mouser.com/ds/2/89/9007_series_reed_relay_datasheet-772252.pdf

    Thassssssit . . . . .


    73’s de Edd
     
    Last edited by a moderator: Apr 22, 2017
  4. beerzinnss

    beerzinnss

    8
    0
    Sep 26, 2016
    As you can see in this page from the datasheet of the CSR8635 bluetooth module
    --> Optional ancillary circuits --> Typical LED's and buttons, the pins are pulled to 1.8V when buttons are pressed (I also see that's the case when checking with a multimeter). I dont see a pulldown here, but I have too little understanding of serious electronics to be able to find something more about the buttons in the datasheet. That's why I posted here, with hopes of someone with an actual education in these things to help out :)
    One thing to point out is that vol- and vol+ buttons are kind of predetermined, others are labeled F2, F3, F4 in this page from the datasheet, so maybe that's a clue why these two are working fine, but others aren't.
     

    Attached Files:

    Last edited: Apr 22, 2017
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Yeah, for those switches shown as connecting directly to the pio, I would try adding a 10k pull down to ground. See if that fixes the behaviour without adding any additional strangeness.
     
  6. beerzinnss

    beerzinnss

    8
    0
    Sep 26, 2016
    Ok, will try that and report back! thanks!
     
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