Stereo Sensor

 

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Stereo Power Detector

Purpose: To know when a Stereo is on or off.

If you install an intelligent open air microphone system it will be important to mute microphones in some locations when a source of noise turns on.  In my house there are a few stereos, that when turned on, interfere with HAL2000.  For example; My wife is in the living room listening to the Back Street Boys and the microphone in that room is picking up the music therefore I am not able to talk to HAL2000 in the bedroom.  

To solve this problem, I built a very inexpensive device using an extension cord, a PowerFlash module, and a relay that will send an X-10 signal to HAL2000.

Of course, this can be used for other applications as well.  I use this sensor to determine if the stereo is turned on when the door bell or telephone rings.  If so, HAL can mute the receiver or pause the CD or DVD.  To save money, HAL always checks to see if we left a TV or stereo on when we leave the house.  Sometimes it's not so obvious if the CD has ended but the receiver is still turned on.  When we arm the security system, HAL pipes up, "Wasting electricity is not cool!  I see you left the living room stereo on, I will shut it off for you now."

relay_all.JPG (94932 bytes)

Rick Tinker gave me the idea for this project.  I really like making these since they are very easy to build and pretty inexpensive.

Important: In order for this to work the stereo must have a "Switched 110V" outlet that turns on and off with the stereo.

I first cut the receptacle off the extension cord, as illustrated in the above picture.  You can chuck this in the trash.  I carefully soldered the A/C extension cord to the connection on the relay that indicates the "coil" which are terminals 7 & 8.  Next, I soldered two 6 inch wires to the normally open contacts of the relay (terminals 6 & 4) and connected them to the PowerFlash module.  Since these are only providing a contact closure, it does not matter which wire on the relay connects to the + or - side of the PowerFlash module.

relay_close.JPG (50015 bytes)

Note: The relay in this picture is a Radio Shack relay part number 275-217D.  It may look different than the one on the web site, but I believe they are identical electronically. I could not find this relay on the web site.

I then set the PowerFlash module to input "B" and Mode "3" which will then send an "on" and "off" X-10 signal when the stereo is turned on and off.

I had to use a lot of electrical tape to cover the terminals, since there is 110 volts under there.  

relay_taped.JPG (77365 bytes)

Next, I set the PowerFlash module to a house and unit code and created an X-10 sensor in HAL of the same codes.  Of course in HAL2000 you can name this sensor something like "living room stereo".  Then I plugged the extension cord into the switched outlet on the stereo receiver and plugged the PowerFlash module into a power outlet.

Now whenever the stereo is turned on HAL2000 knows and can mute the microphones in that area or execute any other actions I can dream up.