Here's a fun
project to make with the
555 chip. It can be built as a stand alone circuit or you can put it
inside a doll, toy or whatever!
Here's how it works. When it's
turned on, the 555 astable oscillators are activated. One will produce
a high pitch squeal through the speaker and the other will blink the
LED about twice per second. When you shield the photo cells
light, the frequency of the sound will decrease and the LED will blink
slower. If you arrange the photo cells so that they are near the LED,
some of the light from the LED will be reflected off whatever is
shielding the photo cell. The photo cell will react to the light and
raise the frequency while the LED is on, then go back to where
was when the LED is off. See the video below for a demonstration.
I encourage you to try building other circuits with the 555. It's a
very versatile chip with many applications.
Have fun and keep on making stuff!