Relay to control appliances connected to pc

AI Thread Summary
To control multiple appliances when a PC shuts off, a relay can be used to manage the power flow. The proposed wiring involves connecting the relay's coil to the PC's power supply, allowing the relay to activate when the PC is on. Concerns were raised about the high coil resistance potentially limiting current flow to the PC. Alternatives like using a power strip with a master switch or USB-controlled power strips were suggested as simpler solutions. Additionally, there are power strips that automatically activate other outlets when current is detected in a designated trigger outlet.
bwana
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when my pc shuts off, i want to shut off a bunch of other things too-speakers, light, monitor.

to do this i need a relay but am a little perplexed on the correct wiring.
(Please ignore the periods. they are necessary to make this drawing look right but have no meaning)

Voltage_____|
. . . . . . . . . .|
1___| . . . . . |
. . . .| . . . . . |
. . .coil = ). . |(
. . . .| . . A. . .B
2___| . . .|
. . . . . . . |
. . . . . . .R1 (lights, speakers)
. . . . . . . |
Neutral__|

When the coil is energized(current from 1 to 2), the switch moves from B to A.

Is it workable to also connect Voltage to 1, then to connect 2 to the hot leg of the pc power cord and then the neutral leg of the pc power cord to neutral? It would look like this:

Voltage_____|
| . . . . . . . . .|
1___| . . . . . |
. . . .| . . . . . |
. . .coil = ). . |(
. . . .| . . A. . .B
2___| . . .|
|. . . . . . .|
PC. . . . . R1 (lights, speakers)
| . . . . . . .|
Neutral___|

The idea is to get current to flow through the coil when the pc is on. This allows current to flow through R1. And when the pc is off, there is current through R1.

The resistance through the coil is 2 kOhms and this is an A/C relay rated at 10 amps for 120 volts. or is this stupid because insufficient current will flow to the pc because the coil resistance is so high?
 
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Wouldn't it be a lot easier to just plug everything into a power bar and flip the master switch?
By the bye, on any of my non-portable Macs the shutdown automatically kills power to the monitor.
 
You can buy a USB connected power stip from from ecostrip for a ridiculous amount of money (thinkgeek used to do a cheap one)
Or if you google usb controlled power strip there are dozens of DIY versions - you just switch the 110/230V live input line with a 5v relay.
 
tnx.
google found this for me:
http://www.instructables.com/id/SC9F1YAFJKGWVP3/

is there anything google can't do?
 
Last edited by a moderator:
bwana said:
is there anything google can't do?

I'm pretty sure that it can't teach a snake to tap-dance... but who can? :wink:
 
Danger said:
I'm pretty sure that it can't teach a snake to tap-dance... but who can? :wink:

Mel Brooks !

spacemag5.jpg
 
mgb_phys said:
Mel Brooks !

Damn, but you're quick.
Unfortunately, you are mistaken. Since that critter has legs, it is not a snake.
Cudos for your response, though. :approve:
 
There are power strips made that automatically turn on the rest of the outlets when current is detected in the "trigger" outlet. There is a threshold adjustment knob to set the sensitivity of the trigger outlet. They work with about everything once the adjustment is set.

I forgot the company, but they are on the same page as the Kill-A-Watt meter on Amazon, which I can't get to right now.
 
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