I'm looking to simulate click of a button (short circuit) on Android phone.
I plan to use Arduino pro micro (5v) to trigger "the click".
What kind of transistor should I use? Maybe there is some example scheme?
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If you're switching voltage is say 5V from the Arduino, a ubitquitous PN2222 BJT will probably work just fine if you switch it in the saturation zone:
Vbias=5.0-0.7 = 4.3 V=IR R=V/I looking for I < 10mA, R = 4.3/0.010
so R the biasing resistor somewhere around 4300 ohms should easily put the transistor into saturation and only require 10 mA from the pin, well within range. A more standard value will be 4700 ohms, it little lower drain on the Arduino pin and a bit less delivered current with the PN2222's beta.
There are many pages describing the use of transistors as switches; here's just one of countless. . Keys to look for are: