Has anyone here ever noticed that some functions on a tv, dvdr, or vcr
can be performed when the remote control batteries are starting to get
weak, but others can't? I think I have.

I've had two devices, one a vcr, where ON/OFF would not work with weak
batteries, but the other functions would.

(either that or the function broke, but one of them iirc resumed working
when the batteries were replaced. Regarding the other, the batteries
haven't been replaced yet.)

On Mon, 21 Jul 2014 01:19:49 -0400, micky
wrote:

Has anyone here ever noticed that some functions on a tv, dvdr, or vcr
can be performed when the remote control batteries are starting to get
weak, but others can't?

TV remotes use PWM (pulse width modulation). As the battery dies, the
functions that require wide pulses, where the LED is lit almost
continuously, start to fail first. Meanwhile, short pulses continue
to work.

You might take an ordinary digital camera, and point it at the remote
control. You'll probably see it flashing away merrily initially, and
then slowly fade away as the button is held down. I don't think you
can see the PWM effect I mentioned with the camera, but if you take a
photo detector diode, and monitor the output on an oscilloscope, I
think you might see the wider waveforms fall apart as the battery
dies.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 20 Jul 2014 23:04:15 -0700, Jeff Liebermann
wrote:

On Mon, 21 Jul 2014 01:19:49 -0400, micky
wrote:

Has anyone here ever noticed that some functions on a tv, dvdr, or vcr
can be performed when the remote control batteries are starting to get
weak, but others can't?

TV remotes use PWM (pulse width modulation). As the battery dies, the
functions that require wide pulses, where the LED is lit almost
continuously, start to fail first. Meanwhile, short pulses continue
to work.

Ah, great. So my observation was probably correctt.

You might take an ordinary digital camera, and point it at the remote
control. You'll probably see it flashing away merrily initially, and
then slowly fade away as the button is held down. I don't think you
can see the PWM effect I mentioned with the camera, but if you take a
photo detector diode, and monitor the output on an oscilloscope, I
think you might see the wider waveforms fall apart as the battery
dies.

Thanks.

"TV remotes use PWM (pulse width modulation)"

I wouldn't call it that. Yes it is pulses and they are of differing timing, but it is like a pulse train. Usually there is a common sequence in the beginning that IDs the remote to the unit. Then comes the command.

I think PWN implies someting a bit different.

That doesn't make you wrong because some of the commands will have the thing lit longer and use a bit more current.