Electronics 2000

Hello all,

I'd like to be able to turn on a (desktop) computer when the phone rings. I've looked into wake-on-modem and wake-on-LAN, but neither do what I want - I need the machine to be fully off before the signal arrives. So I came across the idea of creating a circuit to detect a ring and hooking its output up across the power switch of the computer. Unfortunately I'm a little unsure as to how to go about building such a circuit - can anyone help please?!

Many thanks.

Hi

Take a look at http://www.epanorama.net/circuits/telephone_ringer.html - there is a schematic about halfway down the page for a telephone ring detector. http://www.aaroncake.net/circuits/pflash.asp extends this to drive a relay, the contact of which can be connected accross the power switch (this will only work for an ATX type supply where only a momentary press is needed, otherwise some latching circuitry is required.

The circuit will need a 5V supply to power the relay, you can take this from the standby power output of the PSU, or an external source. See http://www.helpwithpcs.com/courses/powe ... inouts.htm for the ATX PSU pinout.

Incidentally I thought most modern motherboards powered the (on board) network interface from standby power so that WOL still worked when the computer was off. Certainly all the computers I use maintain the ethernet link when shut sown. Not sure about modem wake on ring though.