detecting that a tv is on

hgupta1

Active Member
I finally decided to get a home theater system. I haven't purchased one yet, but I want it to turn on and off with the TV.


Whats the best way to do this? I've got a homeseer computer and an ELK M1 if that helps me in any way.
 

electron

Administrator
Staff member
To detect the state of a TV, you could use CR magnetics current sensors. If there is some sort of lightsource on the back of the TV (status LED, light coming out of the back of the tv), you could also use a CDS photocell. Both type of sensors can be connected to the Elk M1.
 

mdesmarais

Active Member
The other way to do it is to use a universal remote of some type, with a macro that turns everything on at once. Helps if your components have discreet on/off commands.

Thats assuming that you aren't trying to make the case where someone walks up and hits the TV power switch work.
 

hgupta1

Active Member
Thanks guys. Using a different remote control isn't an option because I really like the ones that came with windows mce (very high WAF), and bought them for every tv in the house (all connected to MCE box)


this tv is relatively ancient (1990 Sony 27"), and so I am sure that it leaks light out the back somewhere.

I'll try to connect it to an m1 which will then turn on the receiver. Are there any receivers that turn the speakers on immediately? I hate that delay that many of the receivers have.
 

mdesmarais

Active Member
Modern receivers have CPUs in them- most take a couple of seconds to boot up. . . not sure I've ever seen a spec for turn on time. . .

Wait- so the remote is already talking to the PC? Is that the only way you turn on the TV?
 

hgupta1

Active Member
The microsoft remote that I am using is the generic one that comes with Windows MCE. It learns volume, and power from the TV remote.

the media center computer is always on, and so the remote is the only way I turn on the TV.
 

mdesmarais

Active Member
hgupta1 said:
the media center computer is always on, and so the remote is the only way I turn on the TV.

Does the media center computer see all the IR from the remotes? Or are you just using the same remote in multiple locations, even those without media center computer(s)?
 

noshali

Active Member
The best way to do this is if you have a TV that has serial rs232 connection. I have aMaxent plasma tv that I control using CQC and can see the status of the TV.

I can also have CQC send a command to the elk like turn off the fireplace lights when the tv power on happens.

I don't know if this is what you were looking for but wife loves it as we have our plasma above the fireplace and when she turns on the tv the light above it go off.

regards,
 

hgupta1

Active Member
mdesmarais said:
hgupta1 said:
the media center computer is always on, and so the remote is the only way I turn on the TV.

Does the media center computer see all the IR from the remotes? Or are you just using the same remote in multiple locations, even those without media center computer(s)?
I've got one media center computer in the basement with basically a big splitter sending audio and video to all the tvs in the house. Each tv uses the same microsoft remote, and the ir signal is transmitted to the basement using powermid -like ir extenders.

We can only watch one thing at a time, but the setup works well for us because there's only two of us, and we always watch tv together.

I thought about having the media center turn on the home theater receiver when it sees the "tv power on" signal, but I have a second sony TV upstairs, and MCE doesn't know the difference between the two.

It looks like I'll have to build a detector using the CR magenetics part that electron made.
 

bfisher

Active Member
One of my friends here on this forum has made a special box for me (actually 2 of them)... each box has 4 inputs - 2 sense power, and 2 sense video. I connect it to whatever I want (TV, VCR, DVD, PS2, Satellite, etc), and then connect it to a single Cat5 wire and connect to my HVPro. Works great.

I've recommended he sell these commercially - not sure if he has yet. If interested, send me a PM and I'll get you his name (there might be a reason he hasn't spoken up here and I don't want to blow his cover).
 

JKnox

Member
bfisher said:
One of my friends here on this forum has made a special box for me (actually 2 of them)... each box has 4 inputs - 2 sense power, and 2 sense video.
<delurk>
That would be me. Bruce is a bit too kind in his praise. :lol:

The first device I made doesn't do video detection properly - it doesn't fire on a totally black screen. The second one works much better. It's a variant of the scheme Frank's using, except I got silly and used a microcontroller to stretch/debounce the vsync pulses from the two separator ics.

For the power detection I use the CR 3110 current tranformers that get talked about here from time to time. It's basically a rectifier,burden resistor, comparator type of design. While it works, I'd like to make it better as well (as in better threshold adjustability).

I don't mind sharing the design for anyone who's interested. While I sometimes think about selling this stuff in kit form, the truth is I really don't have the free time to devote to doing it correctly.

Jerry
 

hgupta1

Active Member
electron said:
To detect the state of a TV, you could use CR magnetics current sensors. If there is some sort of lightsource on the back of the TV (status LED, light coming out of the back of the tv), you could also use a CDS photocell. Both type of sensors can be connected to the Elk M1.
Which is the best CR Magnetics current sensor to get for connecting to an Elk M1?
 
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