Let's Make Robots!


use mains AC as a switch for arduino?

hey gang, does anyone know if it's possible to use mains AC as a switch for the 'duino?

A little background:

Calculon is working on a project that he hopes will take advantage of his doorbell's AC power. He wants the old-school analog doorbell switch to activate a function on his arduino instead of firing off a solenoid in the door chime. Is this possible with some sort of voltage divider? He doesn't need to measure the current, voltage, phase, or anything liek that, he just needs to sense on/off like a pushbutton. He assumes the initial doorbell voltage will be 120V.

AC wall power

I need to power 2 picaxes and 25 LEDs, each with it's own 1k resistor. Also a small DC motor. I would like to use an AC adapter, but only what is necessary (need the others for later). I have three 5V adapters: 250ma, 400ma, and 1A. Which should I use?