help !! photo cell sensor

Thread Starter

feesoo

Joined Mar 3, 2007
4
i have photo cell sensor that contains transmitter (IR LED) and receiver (transistor) i want full design for the signal conditioning unit ,,i have buit many forms but still cannot work .
 

beenthere

Joined Apr 20, 2004
15,819
If you are lucky, the emitter and detector sides are marked E & D, and should also have polarity marks. Otherwise, you wil need the spec sheet from the manufacturer.

The emitter will need between 20 and 50 milliamps current. Chooes a resistor based on the voltage applied. The detector always runs common-emitter, so put the - to ground. IR photons don't carry much energy, so make the collector resistor fairly large. You can adjust for sensitivity by observing the transistor switching - when the collector resistor is too small, the output can no longer go to ground with full illumination.

The signal out is not capable of driving anything without amplification or buffering. Use a FET like a 2N7000 or a high input resistance op amp like an OP27.
 

beenthere

Joined Apr 20, 2004
15,819
I have no idea what specific device you are trying to use. But, the manufacturer will provide a data sheet which will almost certainly illustrate a typical circuit using that device.
 
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