I was sitting in communication class today and had an ah ha moment. We were going over the different type of am transmitters... i have my transmitter working using transformer AA battery and led and aux jack... My problem is the receiver! I am trying to use a photo resister and an LM 382 and cant get it to work... any ideas of what the circuit would look like... I have tried several different Caps and got it to work for a minute but it was amplified enough... just any ideas and just thoughts would help!!!

 

I ... got it to work for a minute...

Here's a thought - do again what you did for that minute!

Your photo resistor may be awfully slow - check its specs. A schematic would help the pros here diagnose your problem.

 

Thanks will do... new to this what programs are good for making schematics?

 

You can use Visio for the basic picture. Or even Paint if you got the time.

 

Ones you know. But really, even a decent photo or scan of a hand-drawn sketch goes a long way.

If you really want to get serious about apps for drawing (and/or simulating) schematics, there are several threads on the topic in these forums. Eagle comes up often but there are other choices. I use a vector drawing program (Freehand, Intaglio are examples) because I've been using it for years and move quickly in it. But it's not dedicated to drawing schematics so I don't recommend that path unless, like me, you already know how to use a drawing app.

 

I use MS Paint with this library of symbols.
I got them from Bill Marsden.

 

By "photo resister", we take it to mean a cadmium sulphide cell. As Wayneh said CDs cells are very slow and depending upon the actual cell, might filter out too much high frequency content. Its an easy way to prove your concept (which has been adequately proven many times). A photo transistor with an optical diffuser in front of it would give results similar to a CDs cell, but with much better frequency response.

 

The schematic capture function of LTspice (a free simulator from Linear Technology) works for me.

 

Thanks will do... new to this what programs are good for making schematics?

When I started doing schematics I used a mixture of clay and a dark pigment encased in a wooden holder. I used this to make marking on processed wood pulp.

There is even a "delete" function on the marking instrument. It's typically pink.

 

I might as well mention one of my first projects as a kid was to make what I called an "optical transistor." I used one output form my stereo to drive a LED which was next to a photo resistor. The resistor went back into the stereo on the other channel so I could hear the output.

No modulation, just base band. Sounded good at the time.