project to make with the
Here's how it works. When it's
turned on by pressing SW1, the 555 astable oscillator is activated. It will produce
a tone through the speaker that can be varied in pitch
the distance between the LED and the photo cell. The photo cell is
mounted at one end of a 1/4" diameter tube which shields it from 99% of
the light. The LED is mounted on a piece of music wire and inserted
into the tube. You change pitch by simply moving the wire in and out.
Move it inwards and get a higher frequency tone. Move it outwards and
the tone goes down in frequency. You can build the device as I have
shown in the pictures and video, or get creative and come up with
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!
2 - 100 Ohm ohm
resistors 1 - Photo Cell also call Light Dependent Resistor (LDR)
1 - 2.2 mF Electrolytic
1 - 100 mF Electrolytic capacitor
1 - Bright white LED
1 - LM555 8 pin DIP timer chip
1 - Small speaker
1 - Momentary push button switch
1 - 9 volt battery
1 - 9 volt battery clip
1 - small perf board to mount components on
Hook up wire
5" length of music wire or large paper clip.