why does the tv transmit infra red

rafhelp

i bought a new lcd flat screen sony tv. nice. but as soon as it is switched on a nearby digital clock, about 1.5 metres away, starts going berzerk, the time keeps changing, the alarm on led flashes on/off etc...

the only way i could stop this was to block the infra red sensor/receiver on the clock.

in case it was the tv remote i took batteries out remote and it still happened.

Is this normal?

My concern is this:
The tv is sending out signals, what are these infra red signals for, what is there target?
the tv should be sending out infra red signals, but only have a receiver for its remote.
would these almost continuous signals being sent out have adverse effects on health or any other hardware nearby?

any one else have this prob?

aerostar

Infra red is heat radiation, you body even puts out infra red radiation, what is happening is that the leds that do your display/backlight are constantly being pulsed on and off, your clock is picking this up and probably because the infrared receiver/decode system in it is of poor quality, it is reacting to the signals.

Not a lot you can do about it but to mask the sensor in the clock.

There were infra red headphones a few years ago, but if you walked under or near a fluorescent light, you just heard a buzz. Similar effect.

The infrared is not dangerous to you or other hardware.

S0litaire

what's the make and model of the TV?

Spank

It's the presence sensor, if there's no movement after awhile i switches off the picture

rafhelp

sony, i know it has a light/ambience sensor

Joe_Bloggs

Congratulations are deserved for isolating the cause of the problem.
Are there any guidelines as to what infra-red radiation TVs typically radiate.

It would take a photo diode, resistor and oscilloscope to find out.

The LED illuminated LCD screens probably use pulse width modulation to vary the brightness.

J_B.

closed

which clock has the infra red sensor, and what's it for? Same socket?

rafhelp

digital clock. different socket. the clock tells you what time it is the whole day long..

closed

rafhelp wrote: »

the only way i could stop this was to block the infra red sensor/receiver on the clock.

I've seen those time keeping devices before, but never seen one with an infra red sensor/receiver or infra red receiver decode system - so if that's correct and your clock has such a sensor, what's it for (auto dimming, remote control, movement sensor, something else), and which clock is it?

mitchellbloke

if its a 3D tv then you may be seeing the active shutter sync signal ...