Relay to control appliances connected to pc

In summary: 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.
  • #1
bwana
82
2
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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  • #2
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.
 
  • #3
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.
 
  • #4
tnx.
google found this for me:
http://www.instructables.com/id/SC9F1YAFJKGWVP3/

is there anything google can't do?
 
Last edited by a moderator:
  • #5
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:
 
  • #6
Danger said:
I'm pretty sure that it can't teach a snake to tap-dance... but who can? :wink:

Mel Brooks !

spacemag5.jpg
 
  • #7
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:
 
  • #8
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.
 

1. What is a relay?

A relay is an electronic switch that can be controlled by a separate electronic signal. It allows low voltage and low current signals to control high voltage and high current circuits, making it useful for controlling appliances connected to a PC.

2. How does a relay work?

A relay consists of an electromagnet and a set of contacts. When the electromagnet is energized, it creates a magnetic field that attracts the contacts, closing the circuit and allowing current to flow through. When the electromagnet is de-energized, the contacts open and the circuit is broken.

3. How can a relay be used to control appliances connected to a PC?

A relay can be connected to an output pin on a PC's microcontroller or interface circuit. When the output pin is activated, it will energize the relay and close the circuit, turning on the connected appliance. When the output pin is deactivated, the relay will de-energize and the appliance will turn off.

4. What are the benefits of using a relay to control appliances connected to a PC?

Using a relay allows for the safe and efficient control of high voltage and high current devices, such as household appliances, using a low voltage and low current control signal from a PC. It also allows for remote control of appliances without the need for physically flipping a switch.

5. Are there any limitations to using a relay for appliance control?

One limitation of using a relay is that it can only control appliances that use AC power. It cannot be used for appliances that use DC power, such as most electronics. Additionally, it may not be suitable for controlling highly sensitive or precise devices as the relay can produce a small amount of electrical noise.

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