driving relays with micro

Hi all,
I am going to control the power connection of a PC with a microcontroller . I am thinking of putting a relay in the smps out of the pc and switch the relay on whenever I ant the pc to be up. What type of relay (power/current rating or other specs) I should use and which microcontroller is best suited for this.

Thanks in advance.

do you just control the power of the computer case or case and monitor?

Monitors consume more power than cases, you most kind of relays are suitable to control such things,

first you should consider how much power it might consume, check this out

https://en.wikipedia.org/wiki/Relay#Machine_tool_relay

talking about the microcont. it depends on what you are intended to do,

if you want to build a circuit that start your comp. at particular time periodes you dont need very improved device, 12cxx or 12fxx is OK

if you want to get more answers you should tell what is your project about clearly.

If your objective is to turn on the PC with a command by the microcontroller then,

Instead of putting the realy at the output of smps(ie switching the supply to motherboard and other peripherals), you can control those ON signal of the smps.

means,when manually you press the start button on the pc, two wires are shorted during that switch action.
Put a relay at that point. ie, instead of shorting those to points manually with the ON button, you are going to do it with a relay and the SMPS turns on.

This would reduce the current rating of the relay, as you are only switching the signal line and not the output line of smps as you mentioned.

In this case a very low rated relay should be fine. look for
Current rating - 1A
Coil Rating - 5VDC
Contacts - SPST,SPDT
(Make: OEN/GOODSKY/LEONE)

Controller too can be a basic one. Look into www.microchip.com for PIC controllers.


cheers!

Hi all,
Thanks for the replies.

>do you just control the power of the computer case or case and monitor?
I am not controlling the monitor.
I want to use the micro board as a programmed switch that will on/off the pc board whenever I want.

Thanks in advance.

For ur application even a less fast controller will suffice(such as 8051) and interms of rating of relay u r controlling a means power requirement will be maximum 500watts so u can use 5A contact rating relay.

Here's another idea.

I've worked on a similar project before and had great luck with using optoisolators to turn the pc on/off. Relays often require external transistors to drive them if your uC can't supply the appropriate current. Optoisolators are also solid state, so they wont wear out over time and they aren't as prone to physical failure.

My optoisolator of choice is MOC3043SR2M (find it on digikey) and it's very easy to use. Just connect the 'Main Terminals' to the ON signal on the motherboard, as cameo_2007 was referring to, and drive the control pins as if you were driving an LED (since that's basically what it is).