# AC sensing relay



## memarcus (Jan 28, 2010)

I just bought an Onkyo TX-SR508 receiver and realized when I opened it that it doesn't have a switched outlet. Does any one know of a cheap or easy way to operate a relay by sensing the receiver's on/off state? I'm putting it in a very tight space and ventilation is concern so I have a pair of thermostat controlled 12VDC fans I'd like to use to help cool it. Problem is that they always spin at a low speed at room temp then as temp rises the speed increases. The idear here is to have a set of contacts closed when the receiver comes on, either by sensing current in the cord or using the RI output of the ipod dock or other method.

I have found some current sensing relay contacts on Digikey that I can couple to the power cord but they're like $60. This just requires to wrap on side of the cord through a coil.

This thing has a universal port for connecting an ipod as well and I'm sure one of the pins has a constant voltage that could be used but I have no idea where to get the pin out. If going this route I'd like to have the proper connector but realize that that accessory will probably be more than the above option.

Any recommendation as to alternate solutions? These are the only two I could think of without cracking the chassis and voiding the warranty and such.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Any recommendation as to alternate solutions?


Nope – I think you’ve about covered it. Looks like your only options are the $60 thing, or just go with a different receiver.

Regards,
Wayne


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## 1hagop (Apr 13, 2010)

Well I had sort of the same issue with my 5007. I have Behringer amps driving my subs. What I did was to buy a IR543 and two X10 appliance modules. I then added commands to my harmony one remote for turning on the two amps with in the macros that turn on activities. The IR543 is a IR to X10 module and is about $23.00, the appliance modules are about $15. If you catch this stuff on sale you can get them both for $30. This is the only way I know to switch an outlet

For my fans on my AVR I used a 4 port usb hub and hooked up 4 laptop cooling fans to it. The usb hub then plugs into my cable box. The fans run all the time but they are quiet and the AVR is cool!


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## glaufman (Nov 25, 2007)

How much are SmartStrips going for? It's a power strip which senses current in one outlet and uses that to switch other outlets.


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## 1hagop (Apr 13, 2010)

glaufman said:


> How much are SmartStrips going for? It's a power strip which senses current in one outlet and uses that to switch other outlets.


http://www.amazon.com/Belkin-Conserve-F7C007q-Energy-Saving/dp/B003P2UMQ2/ref=dp_cp_ob_e_title_1

about $30. I forgot about those!


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## memarcus (Jan 28, 2010)

Excellent info. thanks for turning me onto the smart strip. I had already ordered the relay but I guess I'll have to pay the "stupid tax" of returning it. This is a much cheaper and simpler option at $30. 

The relay from digikey ($72), plus I'd need a project enclosure ($10), panel mount NEMA 15-5 outlet ($10 gotta order several only, 0.50 a piece), and old extenion cord ($5), some DC power jacks ($7) and 2-position connector ($4) to construct the device I wanted the total cost would have been around $125 with all the shipping of different things.

With the powerstrip I can just plug in the wall wart supply for the fans on the slave outlets and it will only power them when the receiver is powered up. I just hope it doesn't draw enough current in standby mode to fool the sensor on the strip, just not sure what technology the sensor is. It shouldn't draw any real power in standby mode. If it's a problem I can use the TV itself as the master device. It should have a large swing between on and off states.

The free registration to these forums just paid for itself! Thanks guys.


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## bambino (Feb 21, 2010)

Would that unit work for turning on proamps or do they draw too much current for a device like that?


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## 1hagop (Apr 13, 2010)

bambino said:


> Would that unit work for turning on proamps or do they draw too much current for a device like that?


Should work just fine. Specs are 15A/1800W. I actually emailed emotiva to ask if it would work because my 5007 does not have a 12V trigger. They said it would however, the amp would just come on and be in standby mode because once again no 12V trigger from my AVR!


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## bambino (Feb 21, 2010)

I was talking to my buddy at work about using a relay off the triggers of the AVR and splicing into a power strip, but it would have to be an AC relay that can handle some voltage plus we aren't sure if this would strain the triggers on the AVR.:dontknow: Sounds like afun project to try but in the end i think the Belkin sounds like a much better solution as wellas easier.:T


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## glaufman (Nov 25, 2007)

What I personally would rather do is plug the wall wart into the switched outlet on the strip and use it to drive the trigger in.


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## bambino (Feb 21, 2010)

That would be much better then cutting, spliceing and hopeing,:T


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