On a sunny day (Fri, 20 Jan 2023 12:27:54 +0000) it happened Clive Arthur snipped-for-privacy@nowaytoday.co.uk> wrote in <tqe1cb$22781$ snipped-for-privacy@dont-email.me:
You could use these in the rear window:
That is true in mains application. A pocket light working from
3 AA's have the leds in parallel. There is a series resistor, possibly to a group of leds. A single led failing has no consequences. The failure modes are dropping from two meters on a concrete flour, and the switch.
It would be fun to connect a photodetector to an amp and headphones and listen to the light in our world, indoors and out. I might do that.
I did that that with a coil and mag fields when I was a kid. It would be different now.
Right, I guess they don't bother me the same way. I'll if I notice any flicker more often in my peripheral vision now that you mention it.
...and leaking batteries.
It'll maybe need to be an amp with a logarithmic gain if you're going to use it both indoors and out, the dynamic range between lighting in an average office and out doors at noontime on a sunny day is like 90 dB.
The visible spectrum covers about an octave, so translate the light frequencies into audio frequencies.
(Not sure how you'd do that.)
I used a solar cell taped to the face of an oscilloscope to demodulate an AM radio signal in high school. I did this because I realized, with a slow scan rate, the brightness would be related to the area the signal occupied on the screen, meaning the amplitude of the signal. It worked! But my electronics instructor thought it had to be the solar cell acting as a diode that was demodulating the waveform. I later realized he had no idea what was going on with that circuit.
Don't think it could be a direct conversion, but using three photodectors like the eye does, you can get an idea of the color and select a frequency to play based on that.
I knew someone with a cochlear implant. She knew a bit about how it worked. I think she said it had only 16 electrodes, yet she could hear music well enough to enjoy it. That impressed me. Imagine how different it could be with 256 electrodes. Music is such a rich medium!
Just use a photo diode, without parallel resistor, and AC-couple it to an amplifier. The logarithmic response is provided by the forward biased diode itself. E.g. 10% modulation, at whatever light intensity, will provide the same AC voltage.
Arie
Just use a photo diode, without parallel resistor, and AC-couple it to an amplifier. The logarithmic response is provided by the forward biased diode itself. E.g. 10% modulation, at whatever light intensity, will provide the same AC voltage.
Arie
We's only want to hear the AC component of modulated lights. A bit of optics, even a cardboard tube, would allow aiming and help reject ambient DC light.
Gain is cheap.
The problem with 'white' LEDs is the degradation of the phosphor with high currents. Running the LED at Imax and the light output will drop significantly after a few hundred or a thousand hours. Running at Imax/2 or even Imax/3 and the light output may be strong after claimed
30000 hours. The efficiency (in lm/W) is also better for the lower current.Reputable LED manufacturers specify the light characteristics well below maximum allowed Imax current, often at Imax/2 or Imax/3 so with IMax=1 A, the characteristics are specified at 350 mA.
Of course, this requires two or three times the number of LEDs to get the same light output and hence the lamp is more expensive, but this extends the usable life time with more than 3 times, thus being more economical in the long run.
If the phosphor were responsible, you'd expect the light output to get bluer and bluer as the lamp aged, which I don't think it does.
The phosphor/fluor is inorganic, so it doesn't degrade the way organic dyes do.
Cheers
Phil Hobbs
RGB detectors could work for a single tone, but I was hoping for polyphony. Simply divide the light frequencies by 2^39 or 2^40. Jan could probably do it with a PIC.
I just remembered - my great niece has a toy Xylophone with a single octave and the notes are coloured like a rainbow.
Yeah, they have a special instruction on the PIC for that, but it takes 2^39 cycles. Probably added just for Jan, knowing how many of the devices he uses.
LOL, maybe it will sound from the light beams. But isn't each note on a xylophone binary, 1/0? I would think you'd want an analog device.
If you really did that, (not impossible with three sensors, the human eye does it) it would probably sound a lot like noise, unless you had a way to present the sounds in at least 2D. An eye with no spacial distinction wouldn't be very useful, to anyone smarter than planaria.
What sort of processing can turn three receptors, RGB, into a spectrum of color? It might take more than a PIC, just sayin...
An octave or two output is eight to 24 distinct frequencies, not just three. There are linear-array sensors that make a spectrum breakdown for visible light easy with prism or grating, and worst-case the translation to sound from light would just be a 24x24 matrix operating on a 24-element light sensor 'vector'. A DSP processor could handle it fine; slight bonus for using multiple high-Q filters on the 24-element output-with-modulation.
I'm talking about sensing the color of light. The human eye uses three wavelength specific sensors to respond to various spectra of light frequencies.
I don't know why you talk about 24 distinct frequencies. The human ear can distinguish much finer resolution in frequency than that!
If you used an array of wavelength specific light sensors, there would be no need for a matrix. Each one would correspond to a wavelength of sound. That would only require a single output channel and it would not require a DSP to handle the processing. An Arduino could do it.
But, mapping that to a sonic output, there's a polyphonic opportunty. Consider the light is actually a complete spectrum (to be mapped to a multiplicity of notes, to make a 'chord').
The idea was to use a non-high-fidelity sonic range, like the two-or-three octave range of telephony, and the diatonic scale, 8 full notes spanning an octave... Visible light (400 to 700 nm) is less than an octave, some modest frequency-gain in the range seemed appropriate.
Or, you could pump energy into a tuning fork array (similar to a music box) and no computation is necessary at all, just a power-of-light dependence for multiple oscillators' amplitudes.
Yes, and color is not a 1D phenomenon.
That's my point. There's a lot more than 8 notes in a music octave. The diatonic scale has 12 notes and musicians often bend those notes. Other scales use even more notes.
Power of light? You've lost me.
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