Identifying Photosensitive/emiting components

[joao felix]

Greetings,

I have this piece of a Slide Projector circuit with 2 components designated as LDI and LRI. Searching the WWW yielded no result.

The closest I got for the LDI is a Laser Diode, because it seems to me that it has that cup-like structure on the middle from where the laser is projected (or is this structure also common to LightED?):

(The pictures are in my 2nd post)

Regarding the component identifyed with LRI, I'm having a hard time believing it can be a LDResistor because of its 3 leads and double serpentine metal filament (right beneath the lens). Additionally, all the pictures of LDResistors I found on the WWW exhibit only 1 of these serpentine filaments. Is it a Phototransistor?

(The pictures are in my 2nd post)

Maybe its just because I'm a newbie to Electronics, but this is making me crazy. Shouldn't there be a standard in designating electronic components? If these are properly identifyed, it's strange that surfing the web provided me with no definitions for LDI nor LRI.

Well, don't mind my grumping; any help is much appreciated.

PS: there are no other markings or attemps of identification on or close to these components, in the circuit.

 

[joao felix]

I guess my ability to display the pictures is rather crude.

I hope that sending them as attachments will work fine.

BRgrds

 

[Reloadron]

LR1 looks to be a LDR (light Dependent Resistor) or commonly called a photocell assuming it is a two lead device. I doubt it has failed as the few I have seen fail had burned sensor elements visible and that one looks fine. If a two lead device place an ohmeter across it and expose to light and dark and see what the ohmeter does.

LD1 looks to be an everyday LED with a clear case.

Those are my guesses anyway.

Ron

 

[MikeMl]

I second Ron's analysis.

 

[joao felix]

Thank you for your feedback. An update on this:

I just finished to assemble the simple circuit tester in Electronics Club site (I have no multimeter yet...) and went on to test the LDI. Although It emmits no visible light, there's is current flowing through it.

Regarding the other component, I want to believe it is something other than a LDR It has 3 leads and the way the double serpentine (beneath the lens) is positioned relative to the "heads/contacts" of those leads reminds me of the EBC trio on a transistor. I'll try to find something on Alldatasheet, maybe.

Many Thanks!

 

[Reloadron]

Three leads, then it is a photo transistor. I didn't pick up in the picture that it had 3 leads. The base can likely be used or omitted as light acts on the base. As to the other it still looks like an LED to me, though I can't understand how a LED (or any light source) could emit light sans current, be it visible or IR light. What makes you think there is no current flow through the device?

Ron

 

[Mr RB]

A lot of those old '70s devices used an MEL12 phototransistor. They were known for being unstable (I've replaced quite a few over the years).

 

[joao felix]

Thank you so much for your continued support on this.

Regarding Reloadron: I mentioned that there is current flowing through the component because I tested it with a simple continuity tester, wich lights a red LED. There is current flowing through the LED, but no visible light is emitted, that's why I suspect it to be infrared.

Just out of curiosity, if anyone knows about Slide Projectors and how this phototransistor/(supose IR emitting)LED circuit works, please tell!

Grazie