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How to make a photo diode detect light? Answered

Can anyone help me to know how can a photo diode detect a light. What I mean is the light sensing circuit which will close the circuit when it detects light. Please help, I do not know anything about photo diodes.
And one more thing, is there a circuit not using transistors for the light detecting circuit? And what difference would it make if it's forward or reversed biased?
Here is the circuit I made. Please tell me if there is something wrong with it



Best Answer 6 years ago

Never run leds in parallel -- each led needs its own current limiting resistor, or minute differences between the different paralleled diodes will cause one to take more current causing a runaway failure.

Use a transistor if you can - they're cheap and easy to calculate.


3 years ago

how can i make a light detecting diode for use a speaker ?

So for anyone who searches and wants to know, you can use a photodiode as a switch. you need a transistor to attach it to the base of the transistor. and the collector to the pos while the emitter to the neg which will act as a switch for the photodiode. when light hits the diode, the voltage created will forward bias the transistor and current flows through. simple.

is a photo diode an IR led?


The 10K resistor ain't going to let more than 0.5mA through it whatever you do, so the LED will never light.

A "photodiode" is NOT a photoswitch - you need a phototransistor, or a transistor and a photodiode to do what you want to do.

You want the photodiode to "trip" the base of a transistor that is handling the power for the LEDs.


Depends on which picture you mean on my screen there isn't a big yellow box so i don't know can you capture a picture a show us.

Pages of them here


what is the large yellow rectangle in the first picture??? tnx for the link