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Complete newbie here. I'm not using the right terms, so my apologies in advance.

The problem is simple. I want my powered computer speakers (2.1) to turn off when the computer is turned off. I have the same problem with my TV - it is connected to another set of powered (5.1) speakers. Right now I leave both speakers (computer/TV) always powered on, which wastes energy.

How can I create a "load sensing relay" which would monitor the power draw of the computer or the TV and if it goes above some threshold, to switch on the power line to the speakers? I'm sure that such thing already exists, but I don't know its name or how to find and buy it or to wire it myself.

I tried with a traditional relay, which was supposed to be driven from a computer/TV's USB port and when it is on, it would switch on the device connected to it. But this didn't work as both computer and TV's USB ports are always powered, even when the devices themselves are powered off.

That's why I want to monitor the power draw from the "input" device (computer/TV) and activate the relay if it goes above some threshhold (as the computer/TV draw some small amount of current even when turned off).

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  • \$\begingroup\$ Why not just use the absence of audio to deactivate the speaker power or speaker amplifier power. You will still need a little residual power for the monitor circuit though. \$\endgroup\$ – Andy aka Mar 24 '20 at 15:08
  • \$\begingroup\$ That residual power will be tiny compared to the benefit of disabling the speakers. I want to apply this idea to other, more power hungry devices in my home as well. Basically I need to find a way how to monitor one device and power off/on other based on its power consumtion. \$\endgroup\$ – georgiptr Mar 24 '20 at 20:25
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I found my answer. It is called a Master-Slave socket outlet.

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