can anyone help me in "light-listener" project

[antoine magdi]

light-listener

hello everyone, i'm working on the project of "light-listener" , i reached to the attached schematics, can anyone discuss how the circuits operates (in detail plz), because i can't understand where is the source of sound and many other points....
THNX IN ADVANCE

 

[srhoar]

A light listener is nothing more than an AM radio. Instead of radio waves it uses light waves.

It is also nothing more than a simple microphone amplifier but instead of a microphone it uses a light sensor.

Your voice on the diaphram of the mic causes movment which is converted to a current and amplified by the circuit.

A light strike a photo reciever which converts it to a current which is amplified by the circuit.

Thie circuit is set up as a current amplifier which in turn is amplified to drive the speaker.

Hope this helps.

Red

Added after 4 minutes:

A quick way to test it is to cut the bottom off a paper cup, and tape tin foil (aluminum foil) to cover the hole. Shine a flash light (electric torch) on the foil and bounce it to the light reciever. Then talk or hum into the cup and you will hear the sounds coming out of the recievers speaker.

Red

 

[antoine magdi]

ya it helped me thnx... but i still have some questions

1)in the first one the (lm358) is an current to voltage converter, so the current from the photo diode is converted to voltage and amplified by the (lm386) ?
2)which circuit is better and why?

 

[srhoar]

Both circuits are pretty much the same. They both convert light to a current (photo-diode) then convert it to a voltage , (across the volume pot), then amplify that (LM386).

Which is better? Depends on your specs. You can build the LM386 circuit then try each of the detectors, just break the circuit at the volume pot input.

You can just build the detector portion and feed it into your stereo (tape or phono input)

If you have a mp3 player-amplifier, just feed it into that.

Start off simple, then build up.

If you have a second stereo, remove the speaker cover, carefully place a small mirror on the speakers diaphram, and bounce a flash light off it to your sensor.

If you dont have a mirror, just lay your speaker down, and place a CD on it and bounce light off of it.

You can try different types of detectors, try a Cds cell or a solar panel. You can even try a regular LED. (They work in reverse also)

Red

Added after 13 minutes:

Just came across this for a different reason, but knew it would apply.

https://www.i-fiberoptics.com/pdf/IF-OVL20.pdf

Check out near the bottom and you will see the circuit.

Note: On figure 12. D1 does not light IF-D92. D1 is just a LED that shows that the circuit has power. It is confusing since on the drawing they look like they go together.

Red