Step 3: The Voltage Regulator
To power the 555, you can use the Snap Circuits B5 block (it is also called a 9 volt Holder and Switch). The advantage to using this block is you can connect a standard 9 volt battery to the block and it will deliver a reliable 5 volts to the 555 through the L7805 voltage regulator circuit (see circuit schematic). The B5 also has two 5 volt outputs--one to power the Theremin and one that you can use to power another device. HINT: since the output of the 555 in Astable mode is a square wave you could use the output for Pulse Width Modulation (PWM) to control a device such as a motor.