Optoelectronics question

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Interesting. The power this will maximally give would be about

The advantage of the MPP is that you get the maximum power.

And if one would use one of those 200 uW/Mhz microprocessors, 2 of these opto-couples in parallel would do the trick.

Interesting thought, although the free-wheeling diode (also 0.6 V) would dissipate about 50% of the power if my intuition doesn't fool me.

joe

I strung a bunch of those together to try and make a ~100V supply. It was ok, but only as strong (current wise) as it's weakest link.

If you look at the numbers you might assume 10-15 photodiodes in series, and so ~1% of the LED current is captured.

George H.

One bad apple will destroy the whole chain.

Define "equal" please.

Is it possible to use a photo transistor as a compact solar cell? How's it work (other than "pretty good" or "real bad")....

Don't have any experience with that.

Yes, but the output will be really tiny.

On Thu, 28 Jan 2016 08:22:01 -0800, John Larkin Gave us:

Probably get more from a resistor bolometer package.

Except that resistors don't generate power like solar cells do.

Den torsdag den 28. januar 2016 kl. 17.12.36 UTC+1 skrev bitrex:

-Lasse

Not if it only has two leads. You can think of a phototransistor as being a normal NPN with a very small photodiode connected from base to collector. (It's actually the collector depletion region that does most of the photodetecting.)

If the base lead is brought out, you can get the photocurrent by connecting C and B to the external circuit, but you'll be very disappointed by how much you get.

If all you have is C and E, then there's a reverse-biased junction in series with the photocurrent, so you don't get any out. Putting the transistor in normal bias lets it work, of course.

Cheers

Phil Hobbs

The worst cell defines the maximum string current, so the best interest is to illuminate the cells evenly.

Nice, thanks for the explanation.

Do they make really tiny solar cells, then? Say, not much larger than the diameter of the LED. Probably not much demand for that.

Circuit would need to be very compact.

Yeah.... they are called photodiodes. :^)

George H.

On Thu, 28 Jan 2016 13:23:43 -0800 (PST), George Herold Gave us:

Chop, chop, old chap.

:-(((((((

That's what's inside a PV optocoupler, or inside an SSR.

What about a PIN photodiode? Area is about 1 cm^2 (or should that be pF^2 :)

joe

Yeah, BPW34 off eBay.

Beware of Electronic Goldmine "FPT 5086 Photodiode (Pkg of 4)" which is actually a phototransistor. I think "FPT" means "Fairchild PT"

seems kind of expensive. when 30mmx30mm is less than a buck.