phototransistor Light sensor using Photo Transistor

Posted on Feb 6, 2014

A circuit which utilizes a photo-transistor to make a light sensitive switch that is when there is no light in room, the led connected to the photo-transistor lights up and when there is light in room, the led connected to Phototransistor turns off Any schematic or circuit diagram would be really helpful. Here is my Implementation on breadboard. Please tell me if this is correct. I tried to

phototransistor Light sensor using Photo Transistor
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make the two lines in parallel. I suspect my connectionof base of the transistor with resistor is wrong, correct me if I am wrong. SORRY I DID NOT HAVE ANY OTHER SOFTWARE TO SHOW MY IMPLEMENTATION SO PLEASE NEVER MIND :). What did you already try and how didn`t it work What resources have you read (vedor app notes, etc. ) and in what way weren`t they clear The Photon Jun 21 `12 at 15:44 PhotoTransistor has 3 legs, emitter, base, collector, where as it has two and the resulting circuit picture doesn`t have phototransistor, it has 2 leg led type sensor Umer Farooq Jun 21 `12 at 16:04 @UmerFarooq, Phototransistors normally have 2 legs, Emitter and collector. Carriers are not injected through the base connection but instead from the light shining there. Is it possible that your phototransistor gives you a base connection to allow you to bias the transistor and then use the light to increase on top of a DC large signal Bias I have used Phototransistors before with only 2 pins multiple times. Kortuk™ Jun 21 `12 at 16:07 EDIT - the breadboard circuit you have added looks correct (though it`s hard to read. ) so go ahead and try it. If it doesn`t work let us know. Maybe change the resistor to 2k or larger if you are worried about blowing the LED. Just to note this circuit will work fine, although Steven`s suggestion is "preferable" in general. I would maybe not change things till you have it working. The reason the circuit is...

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