Comments on: Photo interrupters explained

By: Borgar

Borgar — Tue, 03 Nov 2009 02:00:13 +0000

wow, im so glad i found this, i’va had a couple of these laying around only to frustrate me

but after reading this and a few minuttes trying i got it working

thanks

By: Richard

Richard — Tue, 14 Jul 2009 07:50:53 +0000

With a few of them, and a bit of printed acetate, you can make a rotary encoder that’ll tell you the absolute position of a shaft… might be a cheaper way of getting some positional feedback on all manner of projects if you’ve got the photo-interrupters already lying around?

http://en.wikipedia.org/wiki/Rotary_encoder#Optical_Absolute_Encoders

offers a few clues for anybody who’s not done it before – one challenge might be to figure out allowing for the physical offsets between the interrupters as it may not be possible to stack them in a straight line.

By: Roly

Roly — Tue, 14 Jul 2009 05:04:13 +0000

Googling “photo interrupter” produces 20,000+ hits, many leading to data sheets that are far more informative, e.g.;

http://www.jaycar.com.au/products_uploaded/ZD1901.pdf

and 20+ devices at;

http://parts.digikey.com/1/parts-kws/photo-interrupter

@36chambers – oh the complexity! How about replacing the whole lot with a couple of light dependent resistors (LDR’s) a.k.a cadmium sulfide (CdS) cells, as *direct* light controlled cross-faders? These are as cheap as dirt but can also be found in appliances such as auto-dimming alarm clocks and night lights.

http://www.doctronics.co.uk/ldr_sensors.htm

By: 36chambers

36chambers — Mon, 13 Jul 2009 20:55:14 +0000

Gnuz, reverse engineered the DJ Focus OPtical Fader for Skratch DJ mixers, which is baysically just 2 photo interrupters on either side. When the fader is all the way to either side, the sound from that channel is cut off.

[img]http://img379.imageshack.us/img379/7991/diyopticalfaderpcb5qg.png[/img]

This is compatible with all mixers accepting a 50K ohm fader.

More Details here;
http://www.diyaudio.com/forums/showthread.php?s=&threadid=63585

By: Josh

Josh — Mon, 13 Jul 2009 17:19:25 +0000

@farthead… not all photointerrupters have part numbers stamped on them.

@moogle… a good place to start would be to learn how led’s and transistors work. led’s have a forward voltage drop of approx. 1.7 volts. the other side would be the transistor side.

By: Lyle Hazelwood

Lyle Hazelwood — Mon, 13 Jul 2009 16:09:01 +0000

“I have a box full of 1000X of a part like these but are both pointing out.I can’t figure out how to use them though.”

Yours are intended to see a reflective surface.
a bit of shiny silver tape and you’ll be watching the world go by.

By: farthead

farthead — Mon, 13 Jul 2009 13:22:51 +0000

@Tachikoma you’re joking right? I can buy them all day long.

Digikey, Jameco, most of the surplus places have them. They are ultra easy to source.

By: farthead

farthead — Mon, 13 Jul 2009 13:21:27 +0000

@moogle, there is a very secret thing on the internet called “google” if you go there and type in the super-dooper secret numbers on the side of the device you can get the “Templars secret decoder” that is called a “data-sheet” to give you the holy pinout and example circuit if you are lucky and holy enough.

Or you can learn electronics and how to use a multimeter and pin out a Phototransisitor, or transistor..

It’s a secret site, I got from the super secret google… SHH Dont SPEAK IT”S NAME!

http://www.electronics-radio.com/articles/test-methods/meters/multimeter-diode-transistor-test.php

very few people know abut this, so dont tell anyone!

By: googfan

googfan — Mon, 13 Jul 2009 03:16:15 +0000

they are just leds and phototransistors right?

updated my site. Check it out!!! got a villrad cascade now.

By: cynic

cynic — Sun, 12 Jul 2009 22:08:05 +0000

Fantastic, I just found a few of these in my bits box today and was thinking of testing them out. Printers are full of them.

By: pc486

pc486 — Sun, 12 Jul 2009 21:02:18 +0000

There are more kinds of photo interrupters than what was listed in the article. You’ll also find them as “optical switches.”

The type covered under the article is a very simple and inexpensive type of photo interrupter. The thing to watch out on these types is that they are more analog than digital. Hook this type to a Schmitt trigger (74HC14 will work) if you are having trouble getting clean output.

Some photo interrupters include conditioning and other features. I just picked up some OPB460s (http://www.farnell.com/datasheets/89728.pdf). These include an on-board Schmitt trigger and open collector output with integrated 10k pull-up (OPB461 omits this pull-up).

By: Brian

Brian — Sun, 12 Jul 2009 19:09:10 +0000

@24601: You can find the emitters and detectors in old ball mice, but unless it’s a *really* old mouse, they will be soldered directly to the PCB and not in a nice little enclosure like the one pictured. I’m not saying the individual components aren’t useful, but you have to do more mechanical work yourself to actually mount the separate emitter and detector, etc.

Better sources are devices like printers and scanners where they’re used as limit stops; you’re more likely to find them as nice, easily reusable packages.

By: Jake of All Trades

Jake of All Trades — Sun, 12 Jul 2009 18:41:20 +0000

I have a big photo-interrupter hooked up to my PC o-scope, making a quite handy tachometer for measuring fan speeds and clock pendulum timing. Hurray for tools made from junk!

By: andrew

andrew — Sun, 12 Jul 2009 17:26:50 +0000

@24601: i believe so, I think i still have a few kicking around too.

By: 24601

24601 — Sun, 12 Jul 2009 17:24:41 +0000

can’t you get small versions of these from old “ball” mice?