Can opto-couplers be opened up to be light activated? (ie used for their phototransistor)

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Triode

Well-Known Member
Is there a reasonable way to open up an optocoupler to be light activated? Or is that a extremely delicate operation to attempt?

My son's snap circuits kit has a broken phototransistor. It uses it for several of the projects where light pulses make a tone from a speaker, or a fiber optic cable triggers a motor. It's fun stuff. But his phototransistor got broken off, and the leads snapped off inside so I can't seem to get a wire onto them. I don't have any phototransistors that work with visible light on me, it's just not a component I've had much occasion to use. But I have a ton of optocouplers with NPN phototransistors inside. If not I can put one in my next parts order, but this would get it working soon, and it's been a favorite activity of his while all the playgrounds are closed. Snap circuits have been sort of the science part of his home schooling lately.

Thanks!
 
Basically you want a Photo Transistor. You will need to know whether it is a PNP or NPN. But why cannibalize an opto coupler? Why not buy a PT?
Can we have some photos of the Zone 0?
 
Depends on what facilities you've available... I would have though that if you held it firmly-but-gently in a vise and filed flat down from the top with a fine-ish file you might be able to expose the transistor. If you've a bench grinder available, hold it in a pair of pliers, against the toolrest, and try the same.
Got to be worth a go if you've got optos to spare.

Don't forget to post us some pictures!
 
Get a low power transistor with the type of your preference with metallic encapsulation.

File the top carefully (that means, with patience) and you could get a useful PT. Clean the white goo inside, if any, and you are in business.

Did that with 2N2222, 2N3711 and even with a 2N3055.
 
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Clipping the seam with some micro-side cutters also works. The metal hat lifts right off.

My micro-side cutters were never the same but the students were really impressed with a DIY phototransistor.
 

You were many years too late

The classic example was the OC71 - which was a black painted glass encapsulated germanium transistor.

It was also available as a phototransistor, cunning called the OCP71, at a greatly inflated price.

Needless to say, it didn't take long until enterprising people found that simply scrapping the paint off an OC71 gave you an OCP71 for a fraction of the price.

As a result of this Mullard (the manufacturer) starting using opaque grease inside the standard OC71's.
 
I remember that when I had a early transistor radio to fix, the owner's asked curiously why the volume went up when he opened the back of the radio,
A couple of OC71's used with the paint flaking off answered the question.!
Max.
 
atferrari said:
Get a low power transistor with the type of your preferente with metalic encapsulation.

File the top carefully (that means, with patience) and you could get a useful PT. Clean the white goo inside, if any, and you are in business.
Click to expand...
Just tried it out of curiosity - a BC477 from my misc semiconductors box, RS branded.

It works, no "goo" to clean and a very obvious switch-on effect when exposed to moderately bright light (changing from no reading to 60K on my meter). It would probably need to feed the base of another transistor to function as a serious switch, but definitely a functional phototransistor.

 
gophert said:
Don't fool yourself, @atferrari knowingly brought forward a vintage solution so I don't think it would be possible to be "many years too late". I think YOU just needed to feel smart today - another case of "Nigel-splaining".
Click to expand...

I would say that it is more like a variation of a theme.
ATF suggested opening a metal can
NG suggested scraping the paint from a glass/plastic case.

And all this lead to another case of "gophert-splaining".


Ay up, thes' nowt as queer as folk, tha' noz.

JimB
 
well that didn't work, his kit uses visible light and these gates are all IR.

I do think I have some metal can NPN transistors around, and probably a few hundred in plastic cases. I'll give that a try.

And as for why I'm doing this, well I did order some but this is very educational and I think it's great how my son is into these electronic kits. He's7, if he has to wait a week he may lose interest.
 

You proposed that clear plastic cans and metal cans both hold a photo active semiconductor but claim the concept is somehow completely different In each case. However, my point was, atferrari could not be late for proposing a vintage solution. Do you agree with Nigel that atferrari was "many years too late" with his suggestion as Nigel accused? Or did you completely misunderstand my post?
 
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You can pop the case on a TO-3 package with a vise. Squeeze near the solid end. I remember doing the photo-transistor thing with a HeNe laser.
 
KeepItSimpleStupid said:
You can pop the case on a TO-3 package with a vise. Squeeze near the solid end. I remember doing the photo-transistor thing with a HeNe laser.
Click to expand...
I just gave that a try, there's a type that I have about 200 of that are NPN and the right current rating for his kit. It popped and exposed the die, but in this case it didn't work anymore. I probably cracked it. But with them being worth a few cents each I can afford to give it a few tries.
 
gophert said:
Do you agree with Nigel that @atferrari was "many years too late" with his suggestion as Nigel accused?
Click to expand...
I'd paraphrase it as "It's hardly a new idea".

(And sorry, but you seem to just be picky and argumentative for the sake of it. It's bit like people that jump on a typo or spelling mistake and ignore the main topic in an answer).
 
rjenkinsgb said:
I'd paraphrase it as "It's hardly a new idea".

(And sorry, but you seem to just be picky and argumentative for the sake of it. It's bit like people that jump on a typo or spelling mistake and ignore the main topic in an answer).
Click to expand...

It seems to be his only reason for been here?, perhaps he should get a life?.
 

May I just say I absolutely love the 'hinged' top
 
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