SQUARE WAVE GENERATOR

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here is the schematic for my first finished signal generator! I am really excited to finish my first project within a single month! I learned LOTS of things with this project!

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

COMPONENTS LIST:

9v Battery
SPST Switch (On/Off Switch)
SPDT Switch (Settings Switch)
MOM (ON) Switch (Push to Make)
IC1 - 7805 5v Regulator
IC2 - 40106 Hex Inverter
C1 - 0.1uF Capacitor
R1 - 100K Potentiometer
R2 - 100K Potentiometer
R3 - 10K Resistor
Output - 1/4" Audio Connector




HERES MY FIRST RECORDING WITH THE NEW SIGNAL GENERATOR!

SWITCHES

SWITCHES give you control of your device. They dont need any power to operate, so you can place them anywhere in your circuit to control where the power goes. These are some basic symbols of types of switches we will be using in our circuits. They have their own vocabulary of terms to describe how they work.

The most basic is the ON/OFF SWITCH. These are placed near the positive charge to cut off power at the source. ON creates a CLOSED CIRCUIT and OFF creates an OPEN CIRCUIT.


PUSH TO MAKE SWITCH is a button. When it is pressed down it closes the circuit, when released the circuit becomes open and the power turns off. It is called a MOMENTARY SWITCH. A button like this is used to make doorbells.





PUSH TO BREAK SWITCH does the opposite, when pressed it opens the circuit, when released it closes the circuit. It is also a MOMENTARY SWITCH. We are going to use one of these to create a silence button on the output of the oscillator, this way we can silence the speaker while switching to another frequency. This will give the oscillator a much wider range of uses when we are making music!



A MULTI WAY SWITCH can switch between different settings, on the oscillator it will be a knob. We are going to use one of these eventually to switch between different types of waves (sine wave, square wave, and triangle wave) and also to switch between different frequency ranges (100, 1K, 100K).





.

INVERTER (IC)

INVERTERS are a type of integrated circuit, so they are abbreviated IC even though they have a different symbol. An inverter is also called a LOGIC GATE because it uses a simple logic program to invert the signal coming into it. If the signal coming in is 0, it changes it to 1, if the signal coming in is 1, it changes it to 0. If you connect the output to the input, you have a rapid oscillation between the two values!

.

GROUND

GROUND represents a point of 0v. In larger circuits it is the actual ground, but on our projects it's just the negative battery wire. This symbol shows up because its easier to write this than produce a wire going to the negative battery wire on schematic. Even if they are disconnected in the drawing, they are all actually connected together when building your circuit.

INTEGRATED CIRCUITS (IC)

INTEGRATED CIRCUITS (IC) are miniature electronic circuits. They are housed inside a DUAL INLINE PACKAGE (DIP) which has pins linked to the chip inside. The pins are numbered counter clockwise from the top left, and the top can be discovered by looking for the half circle indentation on the component. These are really sensitive, and if you are soldering you need to use a DUAL INLINE SOCKET (DIL SOCKET). Its basically another plastic component with pins to solder to the board and pin holders that you can just push the IC into when you are finished.

Sometimes there are other labels on the DIP besides number. These do not effect the numbering system, so they replace the number and the pin count remains the same. So if pin 1 was labeled VDD, pin 2 would still be pin 2, not pin 1. Here are some common alternates:

VDD - positive supply
VSS - ground or negative supply
GND - ground or negative supply

ICs are designed to be placed over the cooling area on the breadboard, connecting columns E and F together. This is a photo of the Hex Inverter IC used in the first project.

DIODES (D) + LIGHT EMITING DIODES (LED)

DIODES (D) are components that allow electric current to flow in only one direction, the direction of the arrow on the schematic. The forward direction is the ANODE (A) and the reverse direction is called the CATHODE (K). They have to be connected the right way around or they clearly wont work, but an actual diode has a line signifying the anode on one end to make this easier.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

LIGHT EMITTING DIODES (LED) are type of diode which emits light when electric current passes through them. They are awesome! There are two wires that hang off every LED, the longer one is the anode and the shorter one is the cathode. Like any diode, they have to be connected in the right direction in order to work. LEDs need to have the correct amount of voltage running through them or they burn out. A standard red LED uses 2.0V and .02mA.

To work out what type of resistor to use in your circuit, use this variation on Ohm's Law:

R = (V_S - V_F) / I

• V_S= Supply Voltage
• V_F= LED Voltage

So if the supply voltage (V_S) is 9V in our circuit, and we are using a single red LED which uses 2V (V_F) and needs 20mA (I) we would need a 350 ohm resistor.

• (9V - 2V) / 0.020A = 7V / 0.020A = 350 ohms

It's better to overestimate resistance rather then underestimate and blow your LED, so use the nearest standard value which is higher. In this case, that would be 390 ohms. Don't forget that resistors have a tolerance value, so use that to fall within the range you need!
.

OHM'S LAW (V = I x R)

This formula is going to be super important as we try to build our own circuits and need to determine the correct component for our schematic:

VOLTAGE (V) = CURRENT (I) x RESISTANCE (R)

• V= I x R
• I = V / R
• R= V / I

VOLTAGE is expressed in VOLTS
CURRENT is expressed in AMPS*
RESISTANCE is expressed in OHMS

• volts = amps x ohms
• amps = volts / ohms
• ohms = volts / amps

A trick I learned to remember this formula is to think of each letter as an animal (vulture, iguana, rabbit). The vulture is flying above, and the iguana and the rabbit are below.

• To the Vulture, the Iguana and Rabbit are at the same level. (V=I x R)
• To the Iguana, the Vulture is above the Rabbit. (I = V / R)
• To the Rabbit, the Vulture is above the Iguana. (R = V / I)

*mA = MILLAMP = 1/1000 amp = .001 amp

RESISTORS (R)

RESISTORS obstruct the flow of electric current. They have no polarity (+/-) and can be connected either way in a circuit, so you can't really mess them up. For most of my projects, they are used to control the pitch of the oscillator. The resistance value is measured in ohms. The tolerance is the degree of sway from the value listed. Electronics aren't perfect.

You can identify the resistance and tolerance value from the color bands on the side of a resistor. The first band represents the first digit of the number, the second band represents the second digit, the third band represents the multipler, and the forth band is the tolerance value. For example, a resistor whose first band is yellow, second band is violet, third band is orange, and last band is gold would have a value of 47K with a tolerance of +/-5%.

1. FIRST DIGIT
2. SECOND DIGIT
3. THE MULTIPLIER
4. THE TOLERANCE

Here is a chart I made which explains what each color means. The colors are arranged chromatically, with darker colors having the lowest value and lighter colors have the highest value. Metallic colors go into decimals, with gold being the best, and silver being second.
















Resistors come in really strange values because they work within the tolerance percent ranges, because of the these ranges there isn't a need to make every value of resistor. There are two different series of resistors, but they both repeat in multiples of 10 for higher values.

The E6 series has six values : 10, 15, 22, 33, 47, 68
The resistors from this series all have a 20% tolerance value.
The values go up roughly 50% between each increasing value.

The E12 series has twelve values : 10, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
The resistors from this series all have a 10% tolerance value.
The values go up in smaller increments in this series to compensate for the lower %.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is the symbol for another kind of resistor, a variable resistor or POTENTIOMETER. Really, this is just a knob that you can turn to change the amount of resistance going through a circuit. Different types of potentiometers have different ranges, but they are rated according to the maximum potential value.

.

CAPACITORS (C)

CAPACITORS store electric charge and filter circuits. They come in lots of different shapes and sizes. We will be using unpolarized capacitors for our projects, which are less than 1uF and can be connected either way.

CAPACITANCE is a capacitors ability to store charge, measured in farads (F). Usually very small amounts of farads are used, micorfarads (uF), nanofarads(nF), and picofarads(pF).

1F=1,000,000uF

1uF=1000nF

1nF=1000pF

Capacitors are labeled in several different ways. The larger polarized capacitors (greater than 1uF) have the capacitance written on them. Unpolarized capacitors use a number code:

1. FIRST DIGIT
2. SECOND DIGIT
3. NUMBER OF ZEROS TO GIVE CAPACITANCE IN pF
4. TOLERANCE (J, K or M for ±5%, ±10% and ±20%)

If there is a K, there is no multiplication, that is the actual value of pF. So a capacitor that says "10K" would be 10,000pF. The K can also be used in place of the decimal without changing meaning, so 1K5 would be 1.5KpF or 1500pF. The example of 104M is 0.1uF. (100,000pF = 100nF =0.1uF)
.

BREADBOARDS

A BREADBOARD is a solderless, reuseable construction base for an electronic circuit. It has a metal plate behind it that connects everything, be sure it's attached or it won't work properly. Breadboards are awesome for testing your own circuits without burning yourself with a soldering iron! Although you can still burn yourself on the parts if you aren't careful!

There are 2 types of strips on a breadboard:

TERMINAL STRIPS - main area for components, are connected in rows of 5, and are handily numbered.

BUS STRIPS - provide power to the components, and contain 2 separate columns, supply voltage is marked with a red line, ground is marked with blue or black line

The gap in the middle is called the COOLING AREA. Even in a small circuit, some of the parts get hot, and it's important that they have air flow underneath them.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This illustrates how the breadboard is connected:

SCHEMATICS

SCHEMATICS are a map of an electronic circuit. They are generally read from left to right, top to bottom, with diagram following the flow of energy through the circuit starting from the battery and flowing towards the output, which will be a speaker for our projects. Since we are going to be reading a lot of schematics, it's important to understand how to read them. Im going to redraw most of the schematics I find on the internet (and eventually draw my own schematics) to keep them consistent with how I best understand how to read them.

The various components on a schematic are labeled in the order that the current flows through them. For example, the first resistor passed will be labeled R1, the second will be R2. Every schematic has a COMPONENTS LIST to go with the schematic. This is the detailed list of parts (and shopping list!) that functions as a schematic key explaining what each component is.

Here are a few basic symbols that will be included in every schematics for my project:

This symbol represents the battery. My eventual goal is to have my oscillator powered from a 9V battery adapter, but for many of the earlier projects I will be using an actual 9V battery. The positive wire from the battery clip is red, the negative wire from the battery clip is black.

Wires are represented by straight lines. Wires may overlap on the schematics, but they are only connected if a dot is placed over the crossing point.



This symbol represents the speaker or output signal. On some of the schematics Ive been finding, they just write output, but this is confusing since every electronic component has two wires (a positive and a negative) and I want to know where the other wire goes. It usually goes in the ground. My eventual goal is to have a 1/4" output from every device, so I can connect it to an amplifier, but since I am constrained by what I know in the beginning, my early outputs are a 3.5mm audio connector, or 1/8" output.

FIRST PROJECT

This is my first attempt to create an oscillator, using a schematic that I found at hackaday.com .

ITEM LIST:

IC1 - 7805 5V Voltage Regulator
IC2 - 40106 Hex Inverter
R2 - 100K Potentiometer
C1 - 0.1uF Capacitor
9V Battery Clip
9V Battery
3.5mm Audio Connector





I built it on a solderless breadboard and sent the output signal into my keyboard amp. The finished oscillator sounded like this : listen here

Although it looks simple, it took me forever to figure out how this works. Where the schematics says IC2P, the ground from the IC2 is connected, as well as the ground from the audio connector. What also took forever to figure out was that the Voltage Regular has the three wires arranged positive, negative, ground and not positive, ground, negative as I expected.

I also dont quite understand the 7 and 14 behind the VSS and VDD. The ground on the IC2 comes from the 7 pin, but the supply comes from the 8 pin, not 14. The oscillator actually makes a different sound when connected to different pins between 8-14. Does anyone know why this is? I don't see how it changes the resistance.

THE PURPOSE OF THIS JOURNAL

This journal is a record of my attempts to learn how to build a signal generator. I hope that this journal will help me learn, and that my mistakes may help others in their trials while learning electronics. Comments are encouraged, if you can see that something is clearly wrong or could be made better, please let me know!
.