Idea to check the TV is on

[Zedman]

Hi,

I have a TV attached to a PC on many remote sites and I need to check if the TV is turned on or its failed or stolen etc.

Anyone got a good idea?

I tought I'll stick a small sensor onto the screen's corner and check periodically (10 sec) if there's no sign (just black) it'll think there's something wrong and will try to switch it on. If it doesn't work than it'll sign it to the central PC.

Are there any simpler method?

thanks,
Zedman

 

[Awarapunshee]

Your idea is good. But if there is a black spot in the picture where you installed the sensor, then?. Your TV is still on but ur sensor showed it off. Ofcourse time interval checking may or may not be solution.
One way is to add a relay to the TV switch, whenever TV is ON, relay energises. which reperesent tv is ON, what ever the picture or its quality is.
Other option is if the TV is CRT, then u can detect the HV field.
And so on.

ENJOY!

 

[Zedman]

It'll be a plasma. I tought if there's no light detected for a period of time than we can say it's not there.

Added after 1 minutes:

But we can not modify the TV itself because of the warranty.

 

[Awarapunshee]

Then what about the sound detection along with light? is it possible?

 

[banjo]

Does the TV have any output jacks, like video out? If so, then you should be able to rectify the sync pulses coming out of the jack and produce a DC voltage. If the TV is off or stolen, the jack will not have any signal and the DC voltage will drop to zero.

Another option is to sense the AC current going into the power cord. Basically, you loop one wire of the AC line through a toriod coil. The coil's output is dependent on the current through the wire. Again rectify the AC to a DC voltage and you have an on/off indicator. You can use an extension cord to split the wires apart, so as not to void your warranty. (If you wrap both wire through the toriod, the the net AC field is zero.)

 

[Zedman]

The AC detection sounds good, but will I detect if the TV fails to show the picture (i mean if the screen fails)?

There will be no sound used.

 

[manikandan_5025]

Another option is to sense the AC current going into the power cord. Basically, you loop one wire of the AC line through a toriod coil. The coil's output is dependent on the current through the wire. Again rectify the AC to a DC voltage and you have an on/off indicator. You can use an extension cord to split the wires apart, so as not to void your warranty. (If you wrap both wire through the toriod, the the net AC field is zero.)

 

[banjo]

Ok, your project has what is known as "feature creep". Initially, you wanted to know if the TV was On. You stated that it could have been turned off or may have been stolen. The new feature is that you want an indication that the screen is "healthy".

If this TV is running 24/7 and has a plasma display, you are going to have to physically go to each site and look at the screen. Plasma displays have a very poor useable lifespan when run constantly. Go to any major airport and look at the plasma displays. Many are severely degraded to the point of being unreadable. Sure you can put a photosensor near the screen and detect whether any light is being transmitted. But you still will not know if its readable.

 

[Zedman]

How long is this lifetime you mentoined? Are LCDs better? They will run working hours only but that'll just double the lifetime...

Added after 3 minutes:

I suppose it's measured at least in months, so it's OK to go there to check it approx 3-4 monthly.
Otherwise it's ok to see if it's not stolen etc by checking with a phototransistor.

 

[banjo]

First, all I know is personal observation and what I read on the Internet. I do not own any plasma displays. The often quoted lifetime of the tube is 30,000 hours. This is over 3 years of 24/7 operation.
However, there are serious warning about running the displays with static display screens. Please read

https://www.practical-home-theater-guide.com/plasma-TV-unit.html

Here they seem to indicate that as little as 30 minutes of a static screen can damage the display. Computer generated displays are by nature highly static. The terrible displays that I noticed in airports were tuned to news channels like CNN with scrolling banners on the top and bottom. As I recall, the bad portions of the display were these computer generated scrolling portions.

 

[Zedman]

~3 years will be long enough for us. Than they can replace it when it fails.

thanks