Let’s start with the breadboard. Breadboards are great tools for prototyping circuits. You can plug components right into the holes without having to solder them. Let’s look at how they work…

In the breadboard above, all the holes in the green rows are connected and all the holes in the blue rows are connected. Let’s call the long rows on the sides “buses”. The buses run perpendicular to the rows and they bring power (+) and ground (-) up and down your breadboard. The middle grey space between the blue and green rows breaks the connection between the blue and green sections. It is also conveniently the perfect size for placing an IC chip across that middle gap. Let’s start by placing our Hex Schmitt IC on the breadboard like this…

Also, add two wires between the positive and negative rails on either side of the board. This will allow us to connect power to one side of the breadboard and be able to access it on both sides. Note the subtle notch in the chip and be sure to point that to the left. The numbers don’t really matter and they might get confusing if people have different types of breadboards, just focus on the general orientation for now. This particular IC chip is a 6 voice hex inverter circuit. The pinouts for the chip are as follows…

Starting at the notch, the pin directly left of the notch is pin 1, and the numbering continues in a horseshow end with pin 14 at the right side of the notch. This numbering system is true for most ICs. Looking at the pinouts above, note which pins are pairs (1&2, 3&4, etc). Each of these pairs will create one our synthesis voices. Pin 14 (+) is the power pin, where we give the chip power, and Pin 7 (-) is the ground pin, which connects to ground. Let’s add power and ground to our chip…

Next we’ll add a 10K resistor, a small capacitor, and a photocell to complete one voice of our synthesizer. All three of these components work together to produce the tone. The capacitor is a component that periodically stores and discharges electrons which triggers the IC to switch between high and low states. The size of the capacitor determines the range of frequencies for that voice of the synthesizer. The photoresistor changes the rate at which the capacitor charges, and will be how you dynamically change the frequency of the square wave (within the range set by the capacitor). The fixed 10K resistor conditions the output signal to send to an amplifier or powered speaker. Add the 10K resistor, small capacitor, and a photocell as pictured below using pins 1&2 on the IC to give us plenty of room…

In order to hear the tone we need to add power to our bread board and add an output jack that allows us to connect our circuit to a powered speaker. In the circuit above, I’ve also added a button between the 10k resistor and the speaker — the tone will only play when the button is depressed. Once you’ve added those components, connect a 1/4″ cable between a powered speaker and the output jack and cover your ears.
We just went through a breadboard diagram for this synthesizer circuit, but if things get more complicated, we might need another method for describing a circuit. Enter the dreaded/loved circuit schematic!

This is the exact same circuit as above, but in a modified schematic form (click to enlarge).
In the next sections we will look at adding voices and volume control.