Go Down

Topic: IR Phototransistor pinout/hookup question (Read 15366 times) previous topic - next topic

raschemmel

I've used the circuit described in this article before

raschemmel

Quote
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. 
Maybe so , but they survived more than 75 years but couldn't survive the internet.

OldSteve

Maybe so , but they survived more than 75 years but couldn't survive the internet.
Yeah. They used to be better, I believe, but lost out when they tried to compete with the cheap Chinese stuff I guess.
They were over here in OZ too, but I haven't seen a Radio Shack for many years now.
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.

OldSteve

I've used the circuit described in this article before
While he could do that and use the photo-diode, it's probably better to just buy a 'real' photo-transistor.
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

I am an old campaigner and I love a good campaign.

So, here, my "Detector" (as D.U.T.) findings --



I have the IR emitter pretty close to the detector, 0.1 inches or so.
I do have a light on, so that I can see what I'm doing, which influences the results a tad.
Uninterrupted, unobstructed, there is 0.8V at Vout and 1.4V when I interrupt, or obstruct, the optical path between.
If I place translucent material between (esd mylar bag, old pink anti-static bag), Vout varies with the material's transmissibility.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

OldSteve

#35
Nov 22, 2015, 04:13 am Last Edit: Nov 22, 2015, 04:15 am by OldSteve Reason: Correcting my apalling typing
I am an old campaigner and I love a good campaign.

So, here, my "Detector" (as D.U.T.) findings --

I have the IR emitter pretty close to the detector, 0.1 inches or so.
I do have a light on, so that I can see what I'm doing, which influences the results a tad.
Uninterrupted, unobstructed, there is 0.8V at Vout and 1.4V when I interrupt, or obstruct, the optical path between.
If I place translucent material between (esd mylar bag, old pink anti-static bag), Vout varies with the material's transmissibility.
In the dark, I imagine the collector would go much closer to the 5V rail. (When the beam is interrupted.)
I'm surprised that the output doesn't go closer to 0V than 0.8V with them that close together though.

How hard are you driving the emitter? 100mA?
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

In the dark, I imagine the collector would go much closer to the 5V rail. (When the beam is interrupted.)
I'm surprised that the output doesn't go closer to 0V than 0.8V with them that close together though.

How hard are you driving the emitter? 100mA?
I'm only running about 20mA through the emitter. (The "spec card" states 40mA max for this.)
Changing the Vout pullup to 1kohm: obstructed Vout = 3.9V (also dark, under an old 35mm film holder) and unobstructed = 2.3V
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

OldSteve

#37
Nov 22, 2015, 05:35 am Last Edit: Nov 22, 2015, 05:36 am by OldSteve
I'm only running about 20mA through the emitter. (The "spec card" states 40mA max for this.)
Changing the Vout pullup to 1kohm: obstructed Vout = 3.9V (also dark, under an old 35mm film holder) and unobstructed = 2.3V
You'd get better results with a high-power IR LED. Mine are rated for 100mA continuous, 1A peak. (Everlight IR333-A)
I'm running a 25% duty-cycle, (38kHz), in my current project and driving the IR LED at 375mA, (10 ohm series resistor, 5V supply). Modulated at 1kHz. Great range.
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

You'd get better results with a high-power IR LED.
Likely so, but perhaps somebody else.
My interest is only bringing clarity to the subject at hand.
Over the years they probably used several devices presenting these pairs.
My pack was pretty old. The "blister" had yellowed as well as the phototransistor encapsulant, but I opened it up for the sake of Science - to shed some badly needed light on this matter.

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

OldSteve

Likely so, but perhaps somebody else.
My interest is only bringing clarity to the subject at hand.
Over the years they probably used several devices presenting these pairs.
My pack was pretty old. The "blister" had yellowed as well as the phototransistor encapsulant, but I opened it up for the sake of Science - to shed some badly needed light on this matter.
I think that light was shed when it was realised that 'interestingfellow' really had a photo-diode, not a photo-transistor.
There wasn't actually a need for you to show the performance of your photo-transistor and low-power IR LED.
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

#40
Nov 22, 2015, 04:02 pm Last Edit: Nov 22, 2015, 04:17 pm by interestingfellow
Well, that makes me feel better; I was making a mistake, just not the one I thought.

Thanks, agian, y'all!

(and, no, I didn't notice the lack of transistor symbol, but I won't anymore* ;D )

runaway_pancake

I think that light was shed when it was realised that 'interestingfellow' really had a photo-diode, not a photo-transistor.
There wasn't actually a need for you to show the performance of your photo-transistor and low-power IR LED.
You like to be a real wiseguy.  
"Realized" by whom?  You?  So what?

The OP has no interest in experimentation, nothing is conforming to his preconceptions. And you want to speculate endlessly, from your conceit of authority, based on nothing more than how you figure things ought to be - this part you like, that part you don't, so you make up the rest.
The RadioShack package that the OP's using has a phototransistor, albeit mismarked, but you can persist contrariwise all you like. The only authority here is the data and if the OP could be pulled away from playing with his toys, his admitted primary concern, and actually participate in his subject - then we might have more data.

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

OldSteve

The RadioShack package that the OP's using has a phototransistor, albeit mismarked, but you can persist contrariwise all you like.
Did you bother to read Dave Evans' post, #18?

And no need to get personal.
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

Did you bother to read Dave Evans' post, #18?

Yes, as a matter of fact.
How critically did you read it?
Did you catch the part where he basically didn't know for certain?
"and the detector was a photo-diode (or so the package said - I haven't tested it or used it)! "
In both cases (the OP's and mine) there are mismarkings.  So, we fill our boots and do some intelligent experimenting.
Or just bin the lot.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

OldSteve

#44
Nov 22, 2015, 04:18 pm Last Edit: Nov 22, 2015, 04:27 pm by OldSteve
Well, that makes me feel better; I was making a mistake, just not the one I thought.

So what could I do with the set I have? Or rather, a typical intended purpose?

Thanks, agian, y'all!

(and, no, I didn't notice the lack of transistor symbol, but I won't anymore* ;D )
According to the label, and Dave Evans in post #18, (Edit: concession to 'Runaway Pancake's last post.) it's most likely a photo-diode and not a photo-transistor. I think that's pretty clear, despite what someone else thinks. That's no doubt why it wouldn't work for you, when connected as a phototransistor.

You could make use of it, but you'd get much better performance from a photo-transistor.
There are some photodiode circuits here, but they require additional components to be really useful:-
Photodiode Circuits

For your optical tacho, it would really be best if you could get a phototransistor. (Unless you do feel like adding a transistor or op-amp to the photodiode for experiment.)
Either way, let us know how you go. :)

Edit: You could set up a test circuit, I guess, just to verify exactly what it is. Just copy the photodiode/transistor circuit from the Google image search link I posted. This one or similar:-
http://farm9.staticflickr.com/8378/8455949720_0ccc37ff2b.jpg
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