This small-but-mighty pocket synthesizer can be used to play that tune that is stuck in your head on-the-go, scare away unwanted animals, or to annoy the heck out of your friends and family. The tone is a square wave and depending on what value of the potentiometer you use you can achieve a 6 octave range. Secured in an Altoids mint tin, this device is truly pocket-sized. Lets get started!
1x push button switch
1x 100 ohm resistor
1x 220 ohm resistor
1x NE555 timer chip
1x mini speaker
1x 1uf-100uf capacitor
1x 2.2uf capacitor
1x 9v battery and clip
1x bright white or blue LED
Some perfboard, solder, soldering iron, and wire
Step 1: The Basics
So how does this thing work? When it comes down to it, it is an astable 555 timer circuit. The LED is placed so that it shines on the photocell. Depending on the strength of the LED, the photocell sends a frequency to the speaker which then emits a sound. The LED is dimmed and brightened by the potentiometer which in turn varies the frequency that comes out of the speaker. A capacitor takes out the DC which comes from the output pin (pin 3) of the NE555 chip which then runs to the speaker. The other end of the speaker is grounded. Now that you know how it works, you are ready to build it!
Step 2: The Schematic
A few things to remember:
The photocell value doesn't matter, just use one that can get enough light.
I tried using a 4.7uf capacitor in place of the 100uf capacitor and it worked fine. My point is that this is a flexible circuit. Don't be afraid to substitute parts to find what works best for you.
I would use a 2.2uf capacitor for the 1uf-10uf capacitor.
The speaker doesn't have to be 16 ohms, but it works the best.
PLEASE use a bright LED. It will make your life so much easier (and give the synthesizer the best sound).
Build this on a breadboard before you put it on perfboard.
Step 3: Put It Together!
Not much to say here, just put it on a perfboard and into the mint tin! Make sure you face the LED to the photocell so you can get a good sound. If you have any questions, please leave a comment. This is my first instructable so please try to hold your punches. Have fun!