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Phototransistors

A project log for Low-resolution scanner for cheap data input

Or "let's revive the idea of the punched cards" for our kids' delight, but without the holes

Yann Guidon / YGDESYann Guidon / YGDES 08/02/2017 at 22:242 Comments

@jaromir.sukuba sent me some KPX80

http://www.teslakatalog.cz/KPX81.html

The title of datasheet reads: "silicon planar phototransistor NPN, for photoeletric sensors of punch tapes or positional sensors".

The pitch is 2.54mm, not 2.5, but it's still good for a 5mm pitch.

The remaining question is : what is the spectral response and what type of light should I use ?

The only mention I find is a 2400°C temperature, which might be understood as "warm white"... Some incandescent light would do, it seems. This begs tests !

Discussions

jaromir.sukuba wrote 08/08/2017 at 19:38 point

I suppose the spectral characteristics (did you just assume my spectrum???) is more-less the same as for all modern phototransistors in clear package,, just like https://www.vishay.com/docs/81532/bpw96.pdf so peak around 800nm, with steeper roll-off on longer wavelength and more-less nothing above 1100nm, and somehow less steep roll-off under 800nm, covering all visible spectrum. Your best bet is IR LED, red LED will do the job too.

That 2400°C temperature mentioned is indeed incandescent bulb, used as testing source, for 1PP75 (not your case) and 2856°C for KPX80 respectively. But that's the source they used for characterization, the phototransistor alone has its spectral response given by silicon itself.

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Yann Guidon / YGDES wrote 08/08/2017 at 21:20 point

Thanks !

Yes, red LEDs will be great.

And for parity generation I have some 74HC280 :-)

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