Audible Light Probe

This Instructable is known as the Audible Light Probe and was designed by Forest Mimms III and was first shown in his mini notebook. I laid out the circuit into an easy-to;make, no-solder kit that anyone between the ages of 9 and 99 can make and enjoy

2n3906 transistor

2n3904 transistor

.1uF capacitor

photoresistor

AA battery holder

AA battery

5 tight springs

8 ohm speaker

a small cardboard box

First poke small holes into your cardboard box about 1" apart. Two springs on the top row and three on the bottom row. The key is to make sure you have space for the 3-terminal device, the transistor, to fit between three springs. Label the springs as shown in the picture. Screw the small tightly wound springs into the box so your project resembles the first picture.

First we are going to install the 2n3906 transistor. The transistor has three terminals, the emitter (E), the base (B), and the collector (C) which are identified in the picture when the flat side is held up. Slightly bend a spring and make sure that the transistor is tightly held. Connect E to 2, B to 4, and C to 3

Next we are going to add the 2n3204. This transistor has the same pinout as the other transistor. E to 1, B to 5 and C to 4

Next add the .1uF capacitor. One terminal to 5 and the other to 3

Now for the photoresistor. One terminal to 5 and the other to 2

Now for the 8 ohm speaker. My speaker has a red and black lead, however it does not matter which terminal you use. Connect one terminal to 1 and the other to 3

Insert the battery into the battery holder. Ensure that the (+) lead is red and the (-) lead is black. Connect the red (+) to 2 and the black (-) to 1

Once power is connected you should hear a tone. If your light conditions are too bright you might meed to cover the photoresistor with a piece of tape or your finger. The frequency of the tone will increase as more light hits the photoresistor. Enjoy.