Go Down

Topic: LED as Sensor ?in reverse or forward bias?? (Read 1 time) previous topic - next topic


Jun 20, 2013, 09:01 am Last Edit: Jun 20, 2013, 09:09 am by devendra Reason: 1
I read some post related to this and what I got is LED can generate small photo current when you throw light towards it.
I also tried with LM358(Op-Amp),I connected in reverse bias and got same result.

But my question is when I connected LED Anode to BC547 Base and cathode to GND(as shown in attached file),
I mean in forward bias it worked!and it was able to switch LED on (not fully but ther is "some" light) which is connected to collector?

i mean to use LED as sensor it should work in reverse bias?they why it worked with BC547 in forward bias?please tell me I am very curious to know about this.. :smiley-mr-green:


The LED can make a positive current when connected in forward bias. If it is reversed, it will provide a negative current. The forward bias, as shown in the schematic, is the correct bias to turn on the npn transistor using photocurrent.
I am going to get going.


MITSUBISHI has very nice paper about Very Low-Cost Sensing and Communication Using Bidirectional LEDs



Very neat paper, thanks for sharing. I just might integrate a simple LED communication interface on a project I'm working on.

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131