I have a project that I'm currently powering with a AAA battery, providing 1.5v to a simple 555 timer circuit. The output of the circuit goes through a voltage divider into the microphone input of a tablet or mobile phone to be measured, i.e. with an oscilloscope app.
Is there a reasonable way to remove the battery from the circuit? When I measure the output of the mic pin with nothing else attached, I get anywhere from 1.5v to 3v, depending on the phone/tablet. Can I draw on this power from the microphone port to power the timer, and still measure the output using the mic?