"Signal sensing" power strip

The Clapper? (modified to accept an external signal instead of its built in mic).....

This unit will work if you have a 12v trigger:

http://www.nilesaudio.com/product.ph...rdcdID=FG00242

Also, the manufacturer of the Smart Strip also has voltage (LEG Series) and USB (LUG Series) sensing controlled strips. They are available in their online store.

http://bitsltd.net/SmartStrip

This unit would be easy to build but you would need to build in delays so quiet passages like between cuts would not bee seen as an OFF trigger.

If the unit switches ON when it sees audio, how would you want it turned off? Timeout after no signal plus a manual shutdown?

One method is to use an LM3915 VU meter driver chip with a long duration time delay trigger circuit on the output. The system would sense an audio signal and trigger an opto-isolated solid state relay for an outlet strip.

The audio signal would continually reset the timer so it would never time out until there was a silence of say, 5 minutes- then it would shut off the power. The audio feed to the amp would be muted until the amp was powered up, then it would fade in so as to eliminate any sudden pop.

It could be configured with a manual ON/OFF trigger as well.

Let me do a little breadboarding to put the basic unit into operation.

I haven't had time to get to the shop to breadboard the controller yet, but it is on the docket.

With a quick google search, I found this circuit. It seems logical and has low component count. The link has a description of how it works and how to adjust sensitivity.

http://sound.westhost.com/project38.htm

They're op-amps, two of them are contained in one package.


They're diodes, simple rectifiers.


What do you mean?

KG sorry i have not been in the shop for a while working on your strip. One thing about the schematic shown is quite different from my concept.

The L/R passive mix network will not maintain as much channel separation as the original. There really is no need for a stereo input as any audio signal present will have sufficient level on both channels to allow one to trigger the system.

The downside is that there will be a delay in the audio output as this system detects the audio signal, powers up the strip and the power amps energize. They usually have a speaker disconnect function that delays output until the power supply is fully saturated. The net effect is that the first few seconds of the first musical piece will be lost and the audio will "open" after the song has started.

My design has the same shortcoming but triggers the relay using a VU meter chip like the LM 3915. The sensitivity can easily be adjusted and and there is a settable "no signal " timer that shuts off accurately after a predetermined silent period. This is accomplished using an actual timer circuit that is user adjustable and does not depend on an unknown decay time using a standard R/C combination.

Details of the components are discussed in the link just above the picture I provided.

As Sam64 already answered, the 1458 is a dual op-amp package, the diodes can be 1N4148 or 1N4004 types, whichever is the easiest to find (or is already at hand). They are not critical, so other types may be just as suitable (I shall leave this to the reader). Their basic purpose it to only allow current to flow in one direction.

Hope that helps.

I probably already have everything here. I would to to use a solid state relay as opposed to a mechanical one. The current draw is much less than a coil relay.

I would also include an adjustable timer like a 555 to control the off delay.

If you have not worked with ICs before you may have a few learning curve issues such as controlled heat from the proper style soldering iron etc.

To make it easy, I was just going to use the VU meter board I have and add the extras as necessary. That way you can easily adjust the turn on sensitivity for low level listening.

I have been working on a complicated audio video contract system so yours had to be set aside. I should be back on it in a couple days.

I'm looking for exactly the solution you describe to trigger on my tube amp and speaker subs when an audio level is detected from the airport express. Any luck? I have an electrical engineering degree, but it's been a LOOONG time since I built a circuit so I'm not sure how successful I'd be. Looking to leach off of you guys