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Topic: IR Phototransistor pinout/hookup question (Read 15773 times) previous topic - next topic

runaway_pancake

I think what I showed in #26 is the way to go (despite "phototransitor" (sic).
Have you tried that, exactly?
[I won't guaranty that "digital-worthy" performance can be had from these components alone.]
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

be80be

#46
Nov 22, 2015, 06:24 pm Last Edit: Nov 22, 2015, 06:26 pm by be80be
This is kind of sad the whole problem here is not knowing what the op has forsure.
But be it a photodiode or a phototransistor they both will work for caching the blinks of a ir led.  Even a red led will work.
Quote
A phototransistor is "A junction transistor which responds to incident light by generating and amplifying an electric current. "
A photodiode is "A semiconductor diode which generates a potential difference or changes its electrical resistance when illuminated. "

Now here are some more expanded explanations.

 A phototransistor is a photosensible semiconductor device comprising three electrodes. Light or ultraviolet light activates this bipolar junction transistor.
Illumination of the base generates carriers which supply the base signal while the base electrode is left floating.The emitter junction constitutes a diode , and transistor action amplifies the incident light inducing the signal current.

A photodiode is a semiconductor diode which gives an important photocurrent under illumination.
One type of photodiode uses a p-n reverse biased junction operated below the breakdown voltage. Excess charge carriers or electron hole pairs are generated by photoconductivity with exposition to electromagnetic radiation.Carriers usually recombine quickly , but the ones produced near or in the depletion layer of the junction can cross the junction and give a photocurrent which is superimposed on the small reverse saturation current.
Photodiodes allow the manufacture of devices with a depletion width convenient for best sensitivity and frequency response.
Using a led is good for some things but heres a little wirte up from makezine http://makezine.com/projects/make-36-boards/how-to-use-leds-to-detect-light/

be80be

Runaway Pancake post #26 is the best start at getting this to work the only problem is hooking the IR whatever the OP has right.
If it's a diode it conducts only when light hits it and backward you still get nothing
I would set it up like that and shine IR light on it and test output nothing then swap it's pins around one way it's going to work.
If it doesn't throw it in the trash  and get new one.
Oh and post 26 works for me with radio shacks bagged set.

interestingfellow

I don't have time to try it right now but as soon as I can, I will.
I know I have some 2n7000s with me but I'm not sure about BC547's...

Thank you all again.

runaway_pancake

I found a guy on ebay who had these (276-0142) for sale.  I ordered two packages.
I expected them to be the same.  As fortune would have it - they aren't, exactly.
And who's surprised?

From the front, same label, looks like the same components.



But, on the back - Differences!


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

interestingfellow

I gave up on that dern radiocrack crap. I managed to go home for the holiday, went ahead and pulled out my parts bin, and salvaged some proper printer emiter/phototransistor pairs.  I have 2 pair.  So far, I have verified that my 16x2 lcd works, and have since moved on to testing the phototransistor.

I'll report back, sirs.

DaveEvans

I found a guy on ebay who had these (276-0142) for sale.  I ordered two packages.

From the front, same label, looks like the same components.

But, on the back - Differences!

Anybody want to continue the "conversation"?
Yup - looks like my first and second packages.  My first one had a phototransistor and the detector in my 2nd one really is a photodiode (I checked recently).

be80be

You all do know there are two types of photodiodes Photovoltaics and Photoconductors. And for what most people ask to do the photodiode would be better than a phototransistor. They turn on faster nS where as phototransistors take mS to turn on.

runaway_pancake

Yes, the devices in my two packs tested as photodiodes. A voltage develops across them when they're exposed to light (more light, more volts), that's how to tell.
And the circuit in Reply #26 is a good one. I think that it is improved with the addition of a diode on the output, to block a negative voltage there when it's heavily illuminated (so to say.)  I was running 60mA or so through the IRED - with the devices coupled dome-to-dome.
At the pullup to cathode junction the voltage was 5V 'dark' and -0.5V with IR, through the diode that was 4.6V 'dark' and -0.1V with IR.
They have a susceptibility to visible light which may effect the test results. I used an old film plastic film holder as a shroud.

I like data.

[@be80be - I think you mean that there are two ways to use photodiodes.]
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

be80be

#54
Dec 02, 2015, 02:30 am Last Edit: Dec 02, 2015, 02:52 am by be80be
Nope there are two types for real they look the same but don't work the same so you really have three kinds to deal with from radio shack a real phototransistor and Photovoltaics and Photoconductors.

You can even use a red led as a Photovoltaics.
Quote
Photodiodes are semiconductors that produce current flow when they absorb light. In application, there are two types of photodiodes: 1) photovoltaics and 2) photoconductors.Photovoltaics work like solar cells (in fact they are the same). When light shines on the photodiode, a voltage is created across it, causing current to flow.
Photoconductors are reverse-biased photodiodes. When light shines on the photodiode, the resistance to the reverse-bias decreases. By measuring the current through the photodiode, you can detect the intensity of light.
Quote
Comparison

Frequency Response
Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds)
Gain
Phototransistors have a higher gain. Photodiodes require an amplifier to use.
Temperature Response
Photodiodes vary less with temperature
Applications

Optocoupler
Optocouplers are used in electronics-sensitive applications. For example, you may use this in a mobile robot application to separate the microcontroller circuitry (low voltage/power) from the motor driver circuitry (high voltage/power).


Well I guess as I think about it you could say there's two kinds or two ways to use a photodiode
But there are photodiodes made to be used just one way and as by product it could work both ways I don't have both of them anymore But one made  current and one didn't.
But the red led makes about 480mA with the IR light at about a haft inch away.

runaway_pancake

#55
Dec 02, 2015, 02:45 am Last Edit: Dec 02, 2015, 02:48 am by Runaway Pancake Reason: add pdf link
be80be,
I don't know what source you're quoting, but there are two modes of operation for any photodiode:
photoconductive mode and photovoltaic mode
I have attached a PDF from OSI Optoelectronics that all interested should find very informative.

> > > Here's a link -- http://www.osioptoelectronics.com/application-notes/AN-Photodiode-Parameters-and-Characteristics.pdf
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

be80be

#56
Dec 02, 2015, 03:14 am Last Edit: Dec 02, 2015, 03:24 am by be80be
References

Fairchild Semiconductor
But I'm talking about real life too back in I think 1986 I got some phototransistors and they had photodiodes two one bag showed how to use as Photovoltaic and worked great just as the bag said the other said it was Photoconductor and it did work to output any current more like a diode that switched with light you could read the resistance change with light. 

runaway_pancake

#57
Dec 02, 2015, 03:41 am Last Edit: Dec 02, 2015, 03:45 am by Runaway Pancake
Photoconductor and it did work to output any current more like a diode that switched with light you could read the resistance change with light.  
Resistance, you say - then they (the contents of that bag) must have been photocells (a/k/a light dependent resistors, LDRs, photoresistors).
You didn't download the AppNote.

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

be80be

You all with the bags that you don't no what your getting I stated a fact the resistance changes in a photodiode
that's use as Photoconductor  which is how the thing was labeled period.
And one is labeled to be  Photovoltaic and they showed how to use them as such period.
I sure I know whats what don't think you'll find any post by me anywhere how to use a phototransistor or a photodiode. And I no what LDR is don't see that looking like a diode in anyways shape or forum.

And I posted quote from    http://hades.mech.northwestern.edu/index.php/Photodiodes_and_Phototransistors
I don't really care if there is one or ten types is this not about someone getting a phototransistor an it being a photodiode and it didn't work as planed this is why there's 3 types in 3 bags and each works differently.
And I'm sure they mixed and matched the bags LOL then printed your parts may be different.

be80be

Does this look like a IR led or Photodiode I don't see it LOL

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