Sensing Preamp On/Off state

[Doug Krasnoff]

Hi all,

I have a yamaha preamp, that has only a single power button. (No separate on and off buttons.)

So, I would like some kind of inexpensive way for homeseer to know if the device is on or off, but I do not want to plug the unit itself into a x10 module or any other module.

I do not know if the audio/video rca outputs have any voltage running through them when there is no signal running through them. In order words, last time I used the preamp I was watching and listening to dvd, but now I just turned the preamp on, but NOT THE DVD PLAYER. So the preamp is on but there may/may not be signal through the currently selected preamp input (DVD). Perhaps someone knows if there is some low background voltage regards of output signal.

The other possible ways to monitor might be-- there is a switched and an unswitched power outlet on the back of the preamp. Perhaps using the switched outlet with some sensor that might be the ticket, but I don't know how. When preamp is ON switched outlet is always on, when preamp is OFF switch unit is always OFF.

Finally, I think there was some x10 magnet sensor that was a ring, and went around the power cord and could sense the magnetic field changed for on and off, but I don't really know anything about it.

Thanks in advance for your suggestions.

--Doug

[mrhappy]

plug a wall wart style power adaptor into the switched output, cut off the plug on the low voltage side of it and wire it to the two screw terminals on an X10 powerflash. When this power adaptor turns on the powerflash will send the on signal, enabling you to see its status in HS. Any adaptor with the voltage of 6-18v should work.

[chewie]

That is a great idea MrHappy, I had kicked this exact question around a few times for doing things like (Motion Off, is everything still on?, Yes, then turn it off) but could not think of a good way to do it without using something like a readable current sensor to measure draw and use a higher reading as a sign that things were still on.

The nice thing I found though is that all my gear has discreet on and off commands, so I just set mine up to send off since if it is already off that does nothing.

[mrhappy]

I can't quite take the full credit, it was mentioned in another thread...my original idea involved relays which was not quite as simple but the same principle. The magnetic current sensors usually have the minimum operating current and i'm not sure that a normal line audio signal would be enough to trigger it...and some appliances in standby may use current that is above the minimum level for the sensor to operate so you never know if the device is actually on or just in standby

I use the kind've same principle on my DVD player, on the scart socket there is a pin which outputs a voltage depending on if the player is on, I just wired this straight into a poweflash and can set events whenever the player turns on.

[Steve Q]

For me the X10 Powerflash approach was probablematic due to all the electronic gear on the same circuit. So I use a Radio Shack 110V DPDT Relay soldered to a power cord which is plugged into the accessory power outlet on the receiver. The relay is connected to a DS10A Wireless door/window sensor. When the relay turns ON the DS10A sends a ON command. This has worked flawlessly for me for the past 3 years.

Steve Q

[donstephens]

Could you elaborate? What is a scart socket and how would one wire it?

Thanks

I use the kind've same principle on my DVD player, on the scart socket there is a pin which outputs a voltage depending on if the player is on, I just wired this straight into a poweflash and can set events whenever the player turns on.

[mrhappy]

Could you elaborate? What is a scart socket and how would one wire it?

Thanks

i'm presuming by this they are not that popular elsewhere in the world but they are relatively common on AV stuff here



The rectangular black socket on the right side has 21 pins, pin 8 is 0v for no signal, 6/12v for either 16:9 or 4:3. Pin 16 also holds a voltage for composite or RGB signals. By wiring pin 21 to a powerflash you get to know that the DVD player is outputting a video signal - the other pins are concerned with audio/video/svideo/rgb etc.

[donstephens]

Thanks;

Yes, that does not look familiar. I wonder if an S-video would do something similiar?