i had tons of theese from various scrap electronics thanks for this now i have some use for them

Posted at 8:00 am on Jul 12th, 2009 by jason

Good place to find stuff like this is from old photocopier machines. You can even find several hall effect sensors if you’re lucky. Having said that, it is trivial to build an opto-coupler/interrupter yourself (if pre-built ones are hard for source).

Posted at 8:52 am on Jul 12th, 2009 by Tachikoma

“to source”, rather.

Posted at 8:53 am on Jul 12th, 2009 by Tachikoma

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.
The photo transistor has 3 pins on it???
I have already toasted 8 of them trying to figure it out.

any ideas?

Posted at 10:02 am on Jul 12th, 2009 by The Moogle

moogle: Phototransistors are still transistors — they still have a base, collector, and emitter. It’s just that incoming photons act as virtual base current. If you want an light blocked -> high output, you’ll want to hook up the phototransistor as Vcc – Resistor – Collector ; Emitter – Gnd

Posted at 10:16 am on Jul 12th, 2009 by rj

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

Posted at 10:24 am on Jul 12th, 2009 by 24601

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

Posted at 10:26 am on Jul 12th, 2009 by andrew

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!

Posted at 11:41 am on Jul 12th, 2009 by Jake of All Trades

@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.

Posted at 12:09 pm on Jul 12th, 2009 by Brian

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).

Posted at 2:02 pm on Jul 12th, 2009 by pc486

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.

Posted at 3:08 pm on Jul 12th, 2009 by cynic

they are just leds and phototransistors right?

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

Posted at 8:16 pm on Jul 12th, 2009 by googfan

@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!

Posted at 6:21 am on Jul 13th, 2009 by farthead

@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.

Posted at 6:22 am on Jul 13th, 2009 by farthead

“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.

Posted at 9:09 am on Jul 13th, 2009 by Lyle Hazelwood

@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.

Posted at 10:19 am on Jul 13th, 2009 by Josh

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

Posted at 1:55 pm on Jul 13th, 2009 by 36chambers

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

Posted at 10:04 pm on Jul 13th, 2009 by Roly

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.

Posted at 12:50 am on Jul 14th, 2009 by Richard

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

Posted at 7:00 pm on Nov 2nd, 2009 by Borgar