Hello, I'm new to this forum; in the early 90's I helped build several electronics projects for my children school projects. One which i'v been searching is a "light meter with an infra-red eye and a small speaker", you could HEAR the captured light intensity spectrum rather than to measure it's intensity. It was so good it would capture a lighting bug's light wave and also my micro wave spectrum, all this from a small booklet sold at Radio Shack stores in the late 80's. Is there anyone in our electronics world that can help me out??, thank you, Michael C.

 

Does this look familiar? There's a few light activated/sensitive op-amp based circuits using a CdS photoresistor but they don't quite meet your description?

 

I have a Mims notebook and two RS transistor books that I was given while in the hospital in the 80s.

Thought I could put my hands on them. All I found was an older RS tube book.

Could be in the attic or lost in a move. I'll keep looking.

 

You're almost certainly referring to one of the many books by Forrest M. Mims III. Optical sensing is one of the areas he excels in.

http://www.amazon.com/gp/aw/s/ref=mw_dp_a_s?k=Forrest M. Mims III

http://www.forrestmims.org/publications.html

 

Since this wasn't feedback or a suggestion for AAC I've moved it to a better location.

 

Radio Shack also used to sell a "solar cell experimenter's handbook" kit that included such circuits.

 

thanks for the quote: I too LOVE Texas.

 

This is pretty crude but it should get you started: You can merely put a Cadmiumdisulphide cell, a speaker and a battery in series and see how that goes. For more sensitivity, you can increase the voltage a little or switch to an earphone.

 

thanks, that just might work for now; Usage of the headphone idea opens up another small project possibility for creating a "high impedance microphone" by adding the carbon core of a dry cell, you'll be able to hear the foot steps of almost any bug out there..thanks again...cafemiguel

 

I have a Mims notebook and two RS transistor books that I was given while in the hospital in the 80s.

Thought I could put my hands on them. All I found was an older RS tube book.

Could be in the attic or lost in a move. I'll keep looking.

Got in the attic today!

 

Saw this post and finally got around to digging into my old RadioShack Mims books. I believe the circuit you are looking for is called the Light Listener and can be found in the Science book. It uses a phototransistor to feed a 741 op-amp and then a 386 amp to a speaker.

RadioShack has now merged the small books into larger ones. I believe said circuit can be found in this book currently available at RadioShack.

If I wasn't for the possibility of some sort of copyright infringement, I'd scan and post the circuit. If you don't want to buy the book, I don't think there would be any harm in me redrawing the circuit though - just let me know.

Also found most of the circuit posted here - it omits the op-amp though.