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I have a Samsung HM1300 headset and want to emulate the call button signal via a microcontroller.

Here is a pic of the inside of the headset:

Device PCB

(Original)

The gold button is the call button. I see the solder points (the 4 points around the button). Do you think it's plausible to solder other wires to those points? I would like to simulate a button press via an Arduino to the Bluetooth headset by soldering wires to the current button circuitry.

What do you think? If I am not clear on the question, please let me know.

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  • \$\begingroup\$ It is possible, if you figure out which pin goes where. If the button is between ground and a pull-up resistor, it can be triggered with a small NPN or N transistor. \$\endgroup\$ – venny Sep 28 '14 at 18:19
  • \$\begingroup\$ Any ideas on how to solder such small points without damaging the board? As far as figuring out which pin goes where, a multimeter should do the trick correct? \$\endgroup\$ – tabchas Sep 28 '14 at 18:21
  • \$\begingroup\$ I can see which pins are being shorted. \$\endgroup\$ – tabchas Sep 28 '14 at 18:21
  • \$\begingroup\$ It is not enough, you need to know which side is positive/negative and strong/weak. Soldering to such small points can be done, preferably under a microscope, with a very thin wire that is glued to the board afterwards. \$\endgroup\$ – venny Sep 28 '14 at 18:26
  • \$\begingroup\$ @venny I just used a multimeter, and found which ports are being shorted. After finding that out, I used a jumper wire and shorted the ports manually, and the button was triggered on my phone. To simulate this short, I can use a standard NPN/PNP transistor correct? \$\endgroup\$ – tabchas Sep 28 '14 at 21:10
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It looks plausible.

Measure the button size, and try to find some at a distributer, look at their datasheet to ensure their is nothing weird happening (like a hidden order connection). That will also tell you the pins configuration.

You might get more confident by practicing on similar buttons, so order some. .

If they are big enough, tack-solder them onto some stripboard/veroboard and practice the modification on them, as well as driving the signal. At least hold them with blutak or hot glue. Practice on them to get a feel for what you are doing. Too much heat might damage the PCB, so try to enue you can do the job with a few seconds on heat.

Use a voltmeter, very carefully, to figure out what the switch is doing. It will either be 'high' (say 3.3V), and when pushed goes 'low' (say 0V), or vice versa.

If it is a simple signal pull-up or pull-down, then you could do that with either an N-Channle or P-Channel MOSFET, which are easy to drive from an Arduino pin, or an NPN/PNP transistor.

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  • \$\begingroup\$ I just used a multimeter, and found which ports are being shorted. After finding that out, I used a jumper wire and shorted the ports manually, and the button was triggered on my phone. To simulate this short, I can use a standard NPN/PNP transistor correct? \$\endgroup\$ – tabchas Sep 28 '14 at 20:38

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