Go Down

Topic: IR Phototransistor pinout/hookup question (Read 15365 times) previous topic - next topic

OldSteve

It makes no difference the color of the case of the LED - only the receiver. You want it to appear black, because that is an IR pass/visible block filter.

liudr, are wet erase black markers transparent to IR?

I would just buy an IR phototransistor. If it doesn't have a black casing, it isn't only IR.
Many with clear cases are sold as IR photo-transistors, as in the link in post #10. Just not intended for use in the open.

And none of this explains why his circuit doesn't work in the dark.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

DaveEvans

OP: You said you "verified polarity of the emitter and the detector."  How did you do that for the detector? 

FWIW, this guy found that "The Radioshack IR pairs are somewhat confusing, in that the IR LED and the detector kind of have "backwards" pins. On the IR LED the long pin is the positive side, whereas on the detector the short pin is the positive side (it was labeled as the "collector" on the diagram on the back of the package I got.)"


Also, it might help if you post the emitter and detector specs that are on the Radio Shack package (or just post a pic of the package).

OldSteve

OP: You said you "verified polarity of the emitter and the detector."  How did you do that for the detector? 

FWIW, this guy found that "The Radioshack IR pairs are somewhat confusing, in that the IR LED and the detector kind of have "backwards" pins. On the IR LED the long pin is the positive side, whereas on the detector the short pin is the positive side (it was labeled as the "collector" on the diagram on the back of the package I got.)"

Also, it might help if you post the emitter and detector specs that are on the Radio Shack package (or just post a pic of the package).
Yep, on my similar IR photo-transistor the short leg is the collector, long leg is the emitter. (Opposite to an IR or normal LED, on which the long leg is always the anode and short leg the cathode.)

With mine, that was clearly shown on the specs, though. Those specs are shown under "Description" in this link:- IR Phototransistor
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

DaveEvans

Radio Shack story:   :)

Three years ago or so I bought an IR emitter and detector, p/n 276-0142, from Radio Shack and the detector was a photo-transistor.   Then a year later I bought another pair, with exactly the same part number, and the detector was a photo-diode (or so the package said - I haven't tested it or used it)! 

These days, I stick to Vishay, Osram, etc.

OldSteve

#19
Nov 19, 2015, 09:17 am Last Edit: Nov 19, 2015, 09:20 am by OldSteve
These days, I stick to Vishay, Osram, etc.
That's probably the best plan. The 38kHz demodulating receivers that I'm using are Vishay. (TSOP4838)
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

liuzengqiang

Wet erase markers work. I have a POV display with clear IR transistor painted with a black wet eraser.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

polymorph

Cool! Good to know.

You have to be specific when you say "paint it black". I was in a conversation with a friend about black lights, and some guy sitting nearby impatiently said "why don't you just paint regular bulbs black? A can of black paint is only $5!" and said it like we were idiots.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

interestingfellow

Thank you for all the info. SOrry I haven't been back. I'm way busy with work right now, and this arduino stuff is in support of my rc habit, so it get's second seat when .  Actually, my heli is broke and i'm trying to build the tach so I can give it a proper diagnosis when switching out components.

Anyway, here's the product package for the set i'm using (I left it high res on purpose, sorry for the inconvenience)

I'll report back if I figure it out.

Thanks, again!

OldSteve

Your pic didn't upload. Too big maybe?
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

interestingfellow

Yes, it was too big, and then I exceeded my post count or whatever...bleh. Here it is.

raschemmel

#25
Nov 21, 2015, 09:47 pm Last Edit: Nov 21, 2015, 09:51 pm by raschemmel

Quote
Yes, it was too big, and then I exceeded my post count or whatever...bleh. Here it is. 
Open the photo with Paint, select "Resize" (upper left corner), type in 50 (%) where you see the "100", click the Floppy Disk symbol SAVE button, and then your photo should be small enough to upload.


Quote
If a bit of reading were all it took for anyone to understand anything, then colleges, teachers, tutors, and forums would all be very unnecessary.
Quote
Often, that's true, but in this case all you had to do was google "phototransistor circuit" or similar. Still, not to worry, you know how they work now. (Didn't mean to sound rude, but my patience gets stretched a little sometimes.  
Now if you could just google "How to draw a schematic..."

FYI, the most expedient method used here on the forum if you don't have ExpressSCH is to simply draw a schematic on a sheet of printer paper using black ink pen , take a photo and upload it.
It is much faster than uploading photos of you circuit. If you have the schematic and you think you miswired it the circuit photo would be useful , but uploading circuit photos because you don't know how to draw a schematic just takes more time.

runaway_pancake

"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

OldSteve

#27
Nov 22, 2015, 12:00 am Last Edit: Nov 22, 2015, 12:18 am by OldSteve
It's not a photo-transistor - it's just a photo-diode, with bad labelling on the pins.
nowhere on that package does it say "photo-transistor", (it does say "photodiode"), although for some obscure reason they've seen fit to label the pins "C", "E", instead of "A", "K".
Didn't you notice there was no photo-transistor symbol on the pack, only two diode symbols?
The "Vf=1.2V" also gives it away. :D
And the flat side is the cathode, as with all diodes. (Ignore the "C" "E" pin labels - they're wrong!)
So, before more time is wasted on this, and before you buy any more parts not suited to your purpose, what's the intended final purpose of the IR LED/IR detector? Remote-control, obstacle avoidance, etc ?
Chances are you'd be better off with a demodulating receiver anyway.

I just went back and re-read your initial post. You're making an optical tacho. So you do want a photo-transistor. You still need to buy one, a 'real' photo-transistor. :)

Here's that package label, cropped to show what's important:-


Also see DaveEvans' reply #18.
(I accidentally partly cut it off when editing, but the part number is 276-0142, same as Dave's.)
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

runaway_pancake

It's not a photo-transistor - it's just a photo-diode, with bad labelling on the pins.

Well then, here's another version of that same pair, different package and set of device details, that should really frost your cookies --



276-142 vs 276-0142
The "detector" has a phototransistor symbol and transistor "specs", but its leads are labeled "A" and "C".
[There's an irrelevant depiction of an optocoupler, or whatever, too (Holy TMI, Batman!) - but the package has two discrete components.]

"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

OldSteve

#29
Nov 22, 2015, 12:50 am Last Edit: Nov 22, 2015, 12:57 am by OldSteve
Well then, here's another version of that same pair, different package and set of device details, that should really frost your cookies --



276-142 vs 276-0142
The "detector" has a phototransistor symbol and transistor "specs", but its leads are labeled "A" and "C".
[There's an irrelevant depiction of an optocoupler, or whatever, too (Holy TMI, Batman!) - but the package has two discrete components.]
That must be the old package that Dave Evans referred to in his post. And yeah, what a f@#$up of a label.
Incidentally, I did a Radio Shack search for the clear-lense photo-transistor the other day, and got an "Out-of-stock" result.

All of this is a good argument for buying from decent suppliers who know what they're doing. Obviously, Radio Shack is not one of those. :D

Edit: Silicon Infrared Phototransistor

Edit2: Sparkfun - Optical Detector / Phototransistor - QRD1114

Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Go Up