help me for detecting device number or code

Thread Starter

milani1387

Joined Nov 23, 2014
13
help me for detecting device number or code
pic1


pic2


pic3


Hello
It seems that it is a thermistor
When I place in front of the fire resistance of the sensor was reduced and decreases.......

I've got this sensor from a pcb circuit.........
That
Application of Circuit is detecting hot metal ..............


please help me for detect code or number or Specifications and part number????

what is the type of sensor????

thrmistor?? or uv?? infrared ??? rtd ???? or????

please help me

thanks
milani.
 

MaxHeadRoom

Joined Jul 18, 2013
26,229
I remember the old Mullard OC71 germanium transistor, I had someone bring me an old transistor radio that used them, he was puzzled about the change in volume when he opened the back of the radio.
I noticed some of the black paint they covered them with had flaked off causing the change in gain when exposed to light!!;)
Max.
 

Thread Starter

milani1387

Joined Nov 23, 2014
13
it have 2 pin and in normal mode the Resistance is infinite....
when place infront of the fire ... it rsistance deacreas to 100 kohm
 

MaxHeadRoom

Joined Jul 18, 2013
26,229
Was it in range of the heated metal?
You could place a 1k resistor in series and use a 9v battery to detect a change in current (voltage across the resistor) when subjected to both heat and/or light, an ordinary ohms range may not offer enough current to fwd bias it.
Max.
 

Thread Starter

milani1387

Joined Nov 23, 2014
13
Was the 3rd lead used in the circuit? or did it fracture since when in use?
Max.
no...
3rd lead did not used in the circuit..... it is cutted
....
all part of the pcb ... it have two op-amp .. a pnp transistor and a lm317 ,

lm311p ... mc1458 op amp
lm317 regulator
and some resistance and capacitor....

it logical output drive whit pnp tr.....
when sensor see a hot metal or a falme it detecte and it logic output switch to zero
 

MaxHeadRoom

Joined Jul 18, 2013
26,229
So it could be a thermal device or if it detects the color emitted we could be back to the light detector, try the test I mentioned it should confirm it , are you looking for a modern sub or trying to find the original #, the one you have still seems to work as you describe it?
Max.
 

ian field

Joined Oct 27, 2012
6,536
in this picture shows it pcb symbols...
please help me for detecting pcb symbol???
Those 2 arrows pointing at the symbol suggest an LDR - but I'm not too sure about the arrow heads enclosed within the symbol.

The glass encapsulated device looks to be constructed like a germanium transistor - the different coloured sleeves on the leads support the idea of a polarised component, the cropped 3rd lead wouldn't be out of place on a photo-transistor.

Others have made references to the OCP71 as being similar, and the OC71 which is usually painted black to keep light out - you can scrape the black paint off, but Mullard protected sales of the OCP71 by introducing blobbing the OC71 crystal with opaque silicone grease.

Germanium transistors of any kind are getting hard to find, you could try an LDR - but not if a fast response time is needed, there are various silicon transistors available, the most common type looks like a 5mm LED with slightly tinted encapsulation.
 

Thread Starter

milani1387

Joined Nov 23, 2014
13
So it could be a thermal device or if it detects the color emitted we could be back to the light detector, try the test I mentioned it should confirm it , are you looking for a modern sub or trying to find the original #, the one you have still seems to work as you describe it?
Max.
hi
plaese help me for finding modern sensor
i want a sensor that senseing hot metal or flame .............
plaese introduce me a sensor ,...............
 

Thread Starter

milani1387

Joined Nov 23, 2014
13
Those 2 arrows pointing at the symbol suggest an LDR - but I'm not too sure about the arrow heads enclosed within the symbol.

The glass encapsulated device looks to be constructed like a germanium transistor - the different coloured sleeves on the leads support the idea of a polarised component, the cropped 3rd lead wouldn't be out of place on a photo-transistor.

Others have made references to the OCP71 as being similar, and the OC71 which is usually painted black to keep light out - you can scrape the black paint off, but Mullard protected sales of the OCP71 by introducing blobbing the OC71 crystal with opaque silicone grease.

Germanium transistors of any kind are getting hard to find, you could try an LDR - but not if a fast response time is needed, there are various silicon transistors available, the most common type looks like a 5mm LED with slightly tinted encapsulation.
i want a sensor with hi response from detecting hot metal or flame ...
ldr sensing light .... and not Thermal resistance .... and Immediate damaging....
i want a sensor that sensing hotmetal or flame ...Have a high thermal resistance ... and not sensing light noise from lamp or Lighting environment ....
i think that it sens infrared or uv from hotmetal or flame or fire...........
Is it true?
plaese introduce me a sensor .......

thanks....

b.milani.
 

ian field

Joined Oct 27, 2012
6,536
That construction looks pretty typical of a diffused alloy germanium transistor.

The European glass encapsulated types are pretty scarce, and Mullard started using opaque silicone grease on the crystal to protect sales of the OCP71.

There might be a few old germanium TO5 can 2N types left on the surplus market, you can file the top off the can and seal the crystal with clear epoxy - but you might find yourself bidding against guitar fuzz-face builders.
 
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