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.)
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.
Ah, great. So my observation was probably correctt.
Thanks.
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.
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