Switch a power supply on and off with a TV?

Discussion in 'The Projects Forum' started by AznGothic, Oct 17, 2014.

  1. AznGothic

    Thread Starter Member

    Feb 17, 2008
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    1
    I have some LED lights that I will be wiring up to a laptop charger that is 120VAC input, 12VDC 4A output. I want these lights to come on and turn off when I turn on and off my TV. Looking at the logic board in the TV, I see a connector with pings going to the TV's power supply labeld 12V, GND, ADJ and ON/OFF. I tested these pins and found the 12V stays on all the time and the ON/OFF gets 5V when you turn the TV on and goes dead when you turn the TV off. Is there a way for me to get the TV to turn the LED power supply on and off? Perhaps cut the 120VAC input line for the power supply and put a relay in there that is tied to the 5V ON/OFF pin in the TV? And which relay would I need to buy to do this? I looked at digikey and I just don't understand all of the relay terminology. I'm assuming what I need is the "Power Relay, Over 2A" and not the "Signal Relay, Up to 2A" but then it talks about coil type, coil current, contact rating, switching voltage, turn on voltage (max), turn off voltage (min).....what? If the idea of putting a relay on the ON/OFF pin to supply 120VAC to the LED power supply would work...I just need the coil to turn the relay on and off using 5VDC and the relay needs to handle 120VAC.

    Is this a good way to do it or is there a better way? And what relay do I need to purchase if this is the way I should do it?
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I would use an SSR rated for ~5A @120Vac on the Load side. They are opto-isolated, and require a minimum of ~3V at 3mA to turn on. The switched 5V would operate a SSR just fine..., drawing less than 5mA. A 5V relay would require 100+mA.

    I would co-locate the SSR with the Power Supply, and run a low-voltage twisted pair between the TV and the SSR.
     
  3. AznGothic

    Thread Starter Member

    Feb 17, 2008
    11
    1
    I'm assuming SSR stands for solid state relay. I thought solid states were surface mount though? And I would put the relay on the neutral not the hot leg on the 120V input right?
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The SSR I am thinking of looks like this image

    You can put it in either leg, but you are slightly less likely to zap yourself while working on it if is in the Neutral Leg
     
  5. AznGothic

    Thread Starter Member

    Feb 17, 2008
    11
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    Those contact legs look pretty thin. It can really handle 120VAC? And I can just solder the wire to it instead of putting it on a circuit board since those are through hole legs?
     
  6. AznGothic

    Thread Starter Member

    Feb 17, 2008
    11
    1
    I don't see a "Edit" button so sorry for the double post but...I'm looking at Digitkey right now under Solid State Relay. The filter options are Manufacturer, Packaging, Series, Circuit, Output Type, On-State Resistance, Load Current, Voltage Input, Voltage Load, Mounting Type and Termination Style. So I'm guessing I would select 5A under Load Current. And I select 120VAC under Voltage - Load? Forgive me if I'm rather dumb about this stuff. I'm still learning. Best way to learn is to do it right? I know enough to not kill myself but not enough to not kill what I'm working on lol.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I whittled the Digikey list down to what I think would work for you, and finally sorted it by price.
     
  8. AznGothic

    Thread Starter Member

    Feb 17, 2008
    11
    1
    Wow, thank you for that.
     
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