Infos about a weird vintage led (or something (?))

Thread Starter

BulbChangeExpert

Joined Mar 26, 2016
54
i had this unidentified light bulb since several:rolleyes: years, it has a diameter of 5mm(ish), i really don't know anything about it (if it's a led or whatever, how to power it...) i took it from a TV of the '60-'70 (likely), they where two, at the times i broke one of em to see what's inside and that whiteish stuff is some sort of silicone semiliquid gel, the envelope is glass, there's that weird little bar into the gel that looks like a semiconductor (?)

(i powerd it... with a dmm in diode test nothing happens, i gradually powered it trought a resistor and nothing more than 30uA flows in both directions even if i apply 24V directlyo_ODSCF5428.JPG )
 

Thread Starter

BulbChangeExpert

Joined Mar 26, 2016
54
thanks... you are probably right, this explains both the 30uA thing, the shape and the fact that it was placed in a visible place, i have to investigate the light response, however i didn't remove any paint
 

Tonyr1084

Joined Sep 24, 2015
4,711
Quick suggestion: If it's an infra-red emitter use your cell phone camera to detect the light. In fact, using a cell phone camera is how I determine whether a TV IR Remote is functioning or not. True, you can't distinguish cycles or pulses, but you WILL get a visual representation on the cell phone screen if the LED is lighting up or not.

This is a case of using the cell phone as a diagnostic tool.

IF, as DodgyDave suggests "it's an IR receiver" then using a scope and a TV remote should trigger it. You WILL have to design a circuit to supply a power source and the IR Receiver to switch it on - either way you'll know for sure what it is. Judging from the picture, I think DodgyDave is probably right.
 

Thread Starter

BulbChangeExpert

Joined Mar 26, 2016
54
Its a photo diode, for infrared remote control signals.
mhhh.. they where two, if i remember well they where the same (looking at em).... maybe one is used for light adaptation and the other... well... maybe as IR receiver... but the TV was from an era that remotes where not experimented yet (maybe)

Quick suggestion: If it's an infra-red emitter use your cell phone camera to detect the light. In fact, using a cell phone camera is how I determine whether a TV IR Remote is functioning or not. True, you can't distinguish cycles or pulses, but you WILL get a visual representation on the cell phone screen if the LED is lighting up or not.

This is a case of using the cell phone as a diagnostic tool.

IF, as DodgyDave suggests "it's an IR receiver" then using a scope and a TV remote should trigger it. You WILL have to design a circuit to supply a power source and the IR Receiver to switch it on - either way you'll know for sure what it is. Judging from the picture, I think DodgyDave is probably right.
it was INTO the TV, i hadn't any remote (the tv was already broken (of course:D))
also i know that IR receivers are extremely sensitive devices that work no good with leads so long on the IR diode
but i have plenty of IR LEDs so exciting it won't be so hard

i'll update you all this evening (italy time zone:rolleyes:)
 

GopherT

Joined Nov 23, 2012
8,012
thanks... you are probably right, this explains both the 30uA thing, the shape and the fact that it was placed in a visible place, i have to investigate the light response, however i didn't remove any paint
With only micro amps of current low, It could be a phototransistor (no external base pin access) or photodiode for an automatic gain control (if there was access to some lamp or tube light source).

On the other hand, it could have been an IR emitter if you tested it without current limiting and fried it to make a open circuit.
 
I really doubt it's a photoelectric device of any kind.

1. You wouldn't put a milky gel into a photoelectric device because that will just decrease the light falling on it.

2. Why would there be TWO of them if it were a remote-control photo receptor or an ambient light compensator?

3. A big bar of something between two electrodes doesn't translate into any photoelectric device I've ever seen.

I think it's most likely a thermistor of some kind, like a "rod" thermistor, and the gel is a heat-conductive grease.

Thermistor_5df879e0ebb2d0329bf3e594e0a0766c2118cfef.jpg thermistor_3.jpg Thermistor_302254_gallery_53f713689ab37_gif_fa_rszd.jpg
 

Thread Starter

BulbChangeExpert

Joined Mar 26, 2016
54
, it could have been an IR emitter if you tested it without current limiting and fried it to make a open circuit.
actually i don't remember if i powered it properly at the times i scavanged it:D but i've read that the BPW34 operates up to 60V

It's surprising just how many devices can be made to operate as IR emitters:).
like anything that is hot?:)

I think it's most likely a thermistor of some kind, View attachment 103244 View attachment 103245 View attachment 103246
no... it was placed at a (semi)visible spot on the TV;)... infact

it's a very nice photodiode:p, a visible spectrum type
right now i don't know how it's possible that it conducts in both directions, but i somehow obtained its response to different light colors
they are....
-110 uA -wood's black light
-230 uA -royal blue
-1300 uA -green
-880 uA -red
-1500 uA -cool white
i loaded it with a 9V batt and a 1k resistor, i used some 5mm clear leds for all the tests exept the black light that is a CFL 26W (face to face the led at 1cm, black light at 10cm)
of course there's the fact that different led colors emit different amount of light, i didn't tested with IR because it's obviously a visible spectrum one, i also suppose it's not a phototransistor

likely it was used for CRT luminosity vs ambient compensation (quite common)
 
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