Once we have learned what electricity is and how to manipulate it to flow around a circuit. The next thing we need to know is what components can we use in our circuit, how do they work and what are their functions. For this tutorial although extensive, it will only focus on the basic components commonly used such as passive components like resistors, actuators like DC motors and sensors alike.
Conductor and Insulators
The first electrical component we will look at is the most basic part and is required in a circuit for current to flow. A conductor is usually a piece of wire (jump cables) or metal that is used to connect different electrical components in a circuit. Not all conductors have the same conductance, remember in the previous tutorial we mentioned that conductance is simply the inverse of resistance so in other words the easier it is for current to flow the better the conductance. Here are some commonly used conducting materials in order of the highest conductance; Silver, Copper, Gold, Aluminium, and Carbon steel.
An insulator, on the other hand, is a poor conductor, in other words, it has a very high resistance such that for all practical purposes we can safely assume electricity does not flow through it. We use insulators a lot in electronics, for example, most electrical wires are covered in plastic for safety purposes, imagine the conducting wires of your kettle were exposed, what is the probability that you will get electrocuted? It is very likely that you will touch the wires while using the kettle and that will be very dangerous. So we use insulators to shield conductors or to prevent our circuit from the flow of current to other things that are not intended to have an electric current. Some of the most used insulators are polymers such as Teflon (PTFE), Polyethylene terephthalate (PET), you will notice most electrical devices such as phones, computers, fridges, tv’s will be covered by some sort of polymer (or plastic) to insulate the internal circuits. Other commonly known insulators are; Wood, Air, Rubber and Glass.
There are 3 primary ways in which people create electrical circuits depending on the application. The first one is just to use conducting wires to connect electrical components, this is fairly easy but not stable. Imagine connecting a battery to a switch and a light bulb, it’s a fairly simple circuit but just using wires alone makes the circuit untidy, unstable and quite big. What we ultimately want is a robust circuit, that is small and efficient like the circuit inside your phone. If you were to use jumper wires to connect all the electrical components inside your phone, the circuit would be bigger than the actual phone. To solve the problem we use Breadboards and Printed Circuit Boards (PCB) to create our circuits. Printed circuits are the ideal way to build circuits because they are small, agile and can easily be replicated for production, this is why they are commonly used in almost all electrical devices including your phone and laptop. The problem with PCB is that they are expensive and time-consuming especially if you are still at prototyping circuit, imagine you solder 30 electrical components in your board then you realize that you need an extra resistor, or you put the components in the wrong orientation, you will have to un-solder your parts or completely scrap the PCB, imagine the time you will waste if you had to do that 10 to 20 times?
An easier way to build circuits while you are still learning or testing your product is to use a Breadboard. A Breadboard comes with easy to connect nodes, conducting wire already soldered and all you have to do is place your components on one of the nodes of the Breadboard. The nice thing about a Breadboard is that you can easily connect and remove components, unlike a PCB where the connection is permanent, this is why Breadboard is so popular for prototyping.
Breadboards are arranged in such a way that each of the nodes in the same row is connected with one conducting wire. Also, each of the rows is not connected to each other. At the far end, you have one two-columns of nodes, the nodes of each column are connected but the two columns are separated. Generally, Breadboards come with two sides which are exactly the same but separated in the middle. The breadboard also has numbering for each node on the Breadboard as can be seen from the image above.
A switch in electronics is an electronic component that can change states in a circuit by closing a circuit or opening it. A simple example will be a light bulb when you switch it on, you are essentially closing the circuit by allowing current to flow, if you open the circuit the current does not flow hence the light bulb does not switch on. There are many different types of switches, the ones we will focus on are mechanical switches.
Single Pole Single Throw Switch (SPST)
This is the common switch found in circuits, it is a single pole meaning it can only control one power circuit, and it a single throw because it can only be switched to one state of the current. This switch allows you to have an open or closed-loop circuit by making a single contact on the circuit.
Single Pole Double Throw Switch (SPDT)
This switch is similar to the SPST switch but the only difference is that it has a double throw, meaning that it can switch two current states, for example, if you have two light bulbs, you can switch between the two off them, if one is off the other one is on and vice versa. Generally, this switch will have three terminals one input, and two outputs.
Push Button Switch
This switch is a momentary switch with a spring mechanism that can cycle between two states and usually starts in a state of being off. This switch is also a single-pole switch but the only difference is that the circuit is only closed when the switch is pressured (button pushed down) and once you let go the circuit becomes open. A good example will be a remote controller, when you turn up the volume you don’t press once and the volume goes up continuously, it will only go up as long as you hold down the button.
This switch has a lever mechanism that can physically be moved to switch between states, they can either be SPST, SPDT and many other variations of switches.
A resistor is a passive electronic component that is used to limit current in a circuit. The resistor is measured in Ohm’s and there is usually a manufacturing tolerance of each resistor that corresponds to how closely resistor is to the specified tolerance. The higher the tolerance the most expensive the resistor will be but also, the more accurate the value will be for the resistor. Resistors also have a unique way of reading their value based on the color bands on them. They usually come in 3 bands, 4 bands, 5 bands, and 6 bands color configuration, for this tutorial we will refer to the 5 color band resistors.
Resistor color bands
The first color band is for the 1st significant digit.
The second color band is for the 2nd significant digit.
The third color band is for the 3rd significant digit.
The value for each color is shown on the figure below
The second last color band is the multiplier
The last color band is the tolerance.
Tolerance is about how close the value is to the one specified by the manufacturer if the tolerance of 10% it means the resistor can potentially be off value by a maximum of 10%. Different resistors have different tolerances depending on the accuracy required for your circuit, obviously, the more accurate your resistors are, the more expensive they become.
Let’s have a look at an example of a 5 band resistor. The first band is green (has a value of 5), the second band is blue (has a value of 6), the third band is black (has a value of 0), the fourth band is orange (x1000) and the last band is brown. Based on the first three colors, our significant digits are 560, the multiplier gives a result of 560K Ohms with a tolerance of +-1%.For information on the color, bands read https://www.allaboutcircuits.com/tools/resistor-color-code-calculator/
A capacitor is a passive electrical component that stores energy in the form of electrical charge while creating a voltage across the plates. A capacitor usually has two conducting plates separated by a dielectric (insulator), because of this, in DC applications, no current will flow past a capacitor but instead, it charges up to its supply voltage. Capacitors are measured in capacitance using units of Faraday (F) which is a measure of capacitors’ ability to store electrical charge.
Light-emitting diodes (LED) are semiconductor light sources that light up when current passes through them. LED’s only allows current to flow in one direction, from the anode to the cathode, that is why they usually have two distinguishable wires at their ends. The longer wire is the anode and the shorter wire is the cathode, when used in the circuit they should be connected such that the current flows from the anode to cathode. Another important fact about an LED is that they usually need small currents in order to work, around 10mA, that is why it is important to find out the maximum current rating of an LED before using it, otherwise, it will be damaged.
A DC motor is an electrical device that turns electrical energy into mechanical energy such as rotation using forces produced by magnetic fields. A typical DC motor will have a fixed rotating shaft that outputs torque and speed depending on the input voltage provided. There are different types of DC motors available in the market place and they mostly differ mostly on the internal mechanical design (stator, armature, commutator) of the motor, efficiency and the power delivered. For most of our electronics projects, we will use DC brushed motors because of the cheap, very reliable and simple control of motor speed. More on DC motors read here.
A servo is similar to DC motors in that they convert electrical energy into mechanical energy but the difference with servo motors is that in addition to having a DC motor they usually have a gearbox, a potentiometer, and a control circuit as well. The advantage of using a servo motor instead of a DC motor is that you can precisely control the position of the shaft and also at any given time you can know the position of the shaft using the potentiometer. A servo will also have at least three pins, one for ground, the other for power and the last one is for the control input of the servo.
As the name suggests an ultrasonic sensor uses ultrasonic frequencies (ultrasound waves) from 20kHz upwards for range finding. The working principle of an ultrasonic sensor is quite simple, there is a transmitting part, receiving and processing part. The first part is when the oscillator sends out ultrasonic waves, they hit a reflective object like a wall, they reflect and are received back by the sensor. The time it takes for the waves to reflect back can be easily calculated in the microcontroller unit like an Arduino then processed to calculate the distance the sensor is from the reflecting object. The ultrasonic sensor is useful in applications that need range finding like an obstacle avoidance robot that can move around without bumping into objects. The ultrasonic sensor module or device will usually have four pins, the first one (VCC) is the voltage supply, the second pin is the input pin (TRIG) which is used to initiate the oscillator to send the signal, the third pin is the output pin (ECHO) which receives the signal and will stay on for the period of time it took the wave to come back, the last pin (GND) is the ground.
The most common method of measuring temperature in electronics is to use a thermistor or a thermocouple, a thermistor is made out of material that changes resistance with temperature. However, these sensors are not very useful when they have to be incorporated into a circuit design, they need to be calibrated and need other devices like an ADC in order to get accurate results. For circuit design, Integrated Circuit Temperature sensors are used which range from -55 degrees to 150 degrees celsius and do not require an ADC. The operation principle is still the same, it measures the resistance of the material and gives the resistance value in digital form. A commonly used temperature sensor like the LM35 will typically have 3 pins, voltage supply, ground and output pin which gives out voltage that is linearly proportional to the measured temperature.