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T H U R S D A Y , J U L Y 2 8 , 2 0 1 1

Remote Power Switch For A Computer, Part 1

My friends know that I am an incredibly lazy person. So lazy that one

of my irritations is that the HTPC (Home Theater PC) in the bedroom

requires that I actually get up out of bed to turn it on. This is fine if I

remember to switch it on before getting into bed, but most of the

time I only remember after I have swaddled myself in blankets.

The solution of course is to have a way to use a remote control of

some sort to turn on the PC. The first option is to not shut down the

PC at all, but leave it in “sleep” mode. This is probably the most

sensible option and I believe that I could set it up so a key press from

my beloved IOGear wireless keyboard would accomplish it. But I don’t

like sleep mode. I like computers to either be on or off. I’m cranky

and old fashioned.

So how then to power on a PC remotely? There are again a couple of

options. I could use Wake Over LAN to start it with the laptop I keep

on the bedside table (roll your eyes). I could use a PS2 keyboard or

mouse to power it on remotely, which would entail some wires strewn

across the floor. I tried to get the USB wireless keyboard to power it

on but was unsuccessful. Possibly I should have tried harder, but I

wanted to try something different.

So my option is an IR remote controlled power switch. The nice folks

at Simerec will sell you a kit or assembled IR remote power switch for

the PC for about $30.00. This is probably the best option so you should

just stop reading this post now and head on over there and order one.

You’re still here? Fine, don’t say I didn’t warn you. I did not buy the

Simerec switch because I’m somewhat cheap (although in the end this

project has cost 10 times that amount as it has spurred on new-hobby-

buying-syndrome). I also was fresh from the high of Henry and my

Awesome Button project and thought that a Teensy would fit the bill.

The Teensy can use Ken Shirriff’s IR remote library to receive and

transmit IR remote control signals. So all I needed was to get an IR

receiver and remote, figure out how to wire it up to receive input,

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Remote Power Switch For A

Computer, Part 2

Remote Power Switch For A

Computer, Part 1

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The Mechanical Philosopher The musings of a dilettante on parenting, mechanics, philosophy and the background noise that is daily life. From beautiful ruralburbian Philomath, Oregon.

of 11The Mechanical Philosopher: Remote Power Switch For A Computer, Part 1

19-08-2013http://mechanicalphilosopher.blogspot.pt/2011/07/remote-power-switch-for-computer...

figure out how to wire a relay to turn the PC power switch on, and

program the thing. Easy! It will practically make itself!

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This is what the code looks like:

#include <IRremote.h>

const int RECV_PIN = 6; // pin that the IR receiver is on

IRrecv irrecv(RECV_PIN); // receive IR on that pin

decode_results results; // the code sent by the remote

int relayPin = 1; // pin out for relay pin and LED

void setup()

{

Serial.begin(9600);

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irrecv.enableIRIn(); // Start the receiver

irrecv.blink13(true);

pinMode(relayPin, OUTPUT);

digitalWrite(relayPin, LOW);

}

void loop() {

if (irrecv.decode(&results)) {

if (results.value != 0) {

Serial.println(results.value);

}

if (results.value == 332 results.value == 2380) {

Serial.println("power");

digitalWrite(relayPin, HIGH);

delay(1000); // waits for a second

digitalWrite(relayPin, LOW);

delay(10000); // waits for 10 seconds

}

irrecv.resume(); // Receive the next value

}

}

The code is simple and I’m not going to go into great detail about it

but basically it starts the receiver, then in the main loop sees if a

button press has been received. If the press is received it prints that

value to the serial monitor (which makes it easy to decode each

button as it is pressed). If the code received is either 332 or 2380 then

the power switch has been pressed. You can look into IR protocols and

learn more if you want. It is fascinating. If the power switch has been

pressed then it sets the relay pin high for one second, then turns it off

and waits ten seconds before resuming the loop. I did this to prevent

accidentally turning it on and off in rapid succession.

Here are two short, grainy and boring videos of my turning the LED on

and off as well as fading it (not applicable to this project, but neat

nonetheless).



Next I had to figure out how to run a relay. Apparently with relays you

need to protect the actuating circuit from the collapse of the coil

field (snore…) which dumps a ton of voltage the wrong way ‘round

into your circuit. This would be bad. So I found a schematic (PDF) that

showed the parts I needed to avoid the problem.

LED off…

LED on…The button is mimicking the 5V signal from the Teensy. The

LED is standing in for the PC power switch.



It’s a simple circuit. The 1N4005 diode was scavenged from the VCR.

My suffering mentor (Thanks Gregg!) told me that a 1N4005 would

work as well as a 1N4004.

This will make it more or less clear. Ok, maybe it won’t. This is the

relay I used.

Then I grafted the IR receiver breadboard to the relay breadboard.



Then I carefully moved all the IR components to the one breadboard. I

tested all along the way to make sure I didn’t make any mistakes.

An extension cord I whipped up runs from the PC power switch header

to the breadboard.

Plugged into the breadboard.



Did it work? Yes. See this incredibly boring and thankfully short video:

More to come in part 2…

Posted by Nick Carter at 1:11 PM

Labels: project

2 comments:

Anonymous said...

Cool! :P

3:52 AM

RFPCREMOTE said...

rfpcremote.com has a rf remote power button.

5:37 AM

Recommend this on Google



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