Automatic speaker control via TV

[Jon] wanted his speakers to come on and off along with his TV. The speaker heats up if left on so he didn’t want to do that. But killing the power also resets the volume level (this is an old set of PC speakers and the remote is wired, not IR) so using one of those switched power strips was out as well. He thought a bit about trying to use the power LED on the TV to build his own circuit when it dawned on him. It’s possible to monitor the USB port on the TV and use it to switch on the speakers.

The circuit above uses a couple of opto-isolators to protect both the television and the speakers. The 5V line from the USB port on the back of the TV is monitored by an XNOR gate (which helps to filter out some of the toggling at power-on). When that gate latches it activates a 555 timer which in turn fires up the speakers. Presumable this happens when power is cut as well, but we’ll let you work through the circuit logic yourself.

Comments

  1. BitMage says:

    *Presumably

  2. echodelta says:

    The speakers have an amplifier presumably inside, if it runs hot it is most likely junk. Get a real amp and speakers and put it on a power strip with the TV they run hot too when off not as much , but they waste power when off. Blame the remote feature with it’s always on power.

  3. Don says:

    This is really neat. I’m using the USB out of my Samsung TV to power my DIY Ambilight on and off as well.

    http://dhowdy.blogspot.com/2011/10/i-have-updated-my-diy-arduino-ambilight.html

    I did not consider using a cap and a 555 to get around the power ‘flip flopping’ while the TV is booting. That’s a great idea. I’ve just dealt with it turning the relay on and off before it stays on.

    I really like how you did this and I think I’m going to use your idea to power both my Ambilight and my Logitech surround sound speakers as well. Great write up!

  4. Spork says:

    Sounds like a good patent to me. I would love if my commercial hardware would power on and off via USB… This could potentially reduce the need for multiple remotes too.

    • NewCommentor1283 says:

      1) i love the simplicity of REAL circuits, as opposed to a whole-entire-computer system! XD

      2) the flip-flopping could be bypassed with a simple RC timer / filter…

      the delay in turning on/off could be seen as an advantage in several ways, or a disadvantage.

      hint: turning the volume (line out TO speakers) down BEFORE making any actual sound… at night

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