I am working on a headphone circuit that plugs into an iPhone , between the mic wire and the GND wire there is the mic , and a push button , with iPhones when you press the button once it will pause/play music , twice will skip too the next song , and three times will go too the previous song , this is all done with one button , however I want too implement 3 buttons for previous song / play-pause / next song , is there any way to implement a button trigger delay so that when I press the forward and reverse button , it will send a signal to the phone that it has been pressed 2/3 times , is there any way of putting in a delay , thanks UPDATE: I have found a step up module from 0.8v too 3.3v , does anyone know how much current I can draw from a 3.5mm socket and whether this will be enough too power a small micro controller such as the Arduino pro mini ? Thanks
The voltage on the mic line is the bias voltage for the electret mic element. I think it comes through a 2.2K or 2.7K resistor. There is not enough current available there to power anything. You're only option is an external power source. One lithium coin cell should last a long time.
Separate from that, your two circuit options are a small batch of CMOS chips or one of the ultra-low-power microcontrollers (PIC, AVR, etc.). If the uC doesn't not have an open-drain option for a GPIO pin, you'll need one external FET like a 2N7000.