A Short Brief

In this meeting we introduced electronic concepts such as voltage, amperage, resistance, power, and Ohm’s law. We also went through a guided lab to figure out rules related to resistors and learned about different electrical components used with IOT (Internet of Things) devices and other electrical systems. The electronics knowledge we taught will be necessary to stay safe, protect your electronics, and design efficient circuits when working with IOT Applications.

Feel free to follow along with the video below or go at your own pace!

What is Electricity?

Conductors vs Insulators

Conductors allow electricity to pass within, meaning that free electrons can move between atoms. They have different resistances to the flow of electrons depending on the type of conductors - superconductors have no resistance. Metals are generally really good conductors.

Insulators don’t allow electricity to pass through, meaning that they resist the movement of electrons between atoms. The reason why lightning travels through air is that if the electrons are strong enough / have enough energy they can change insulators to conductors. Rubbers are generally good insulators.

Charge

You can measure the flow/amounts of electrons with charge. The SI Unit of measurement for charge is a Coulomb which contains 6.24 x 10^18 electrons. Charge is the byproduct of chemical reactions in batteries, heat from nuclear sources or steam, or spinning wind turbine blades. These three examples are similar because they all lead to the movement of electrons, causing them to be charged.

Voltage

Voltage is the stored up energy between two points within a circuit. Its measured in Volts & defined as the amount of potential that leads 1 Joule of energy per Coulomb. This can be thought of through the height of water in a tank - the higher the water level, the more work each unit of water can do. Similarly a higher voltage would mean that each unit of charge has the ability to do more work.

Amperage

Amperage is the amount of charge in a single unit of time. It is defined as 1 Coulomb per second and measured in amps. A way to think about this is the speed of water flow. For example, a high speed of water which is the same pressure of low speed water transfers the same amount of energy, but in a faster time. Similarly, a higher current does the same amount of work as a lower current at the same voltage, but in a much faster time. This could be a potential storage drainer though.

Resistance

The resistance to the flow of electricity is measured in Ohms & is defined to be the resistance that 1 voltage => 1 amp of current. Lesser resistance means a smoother flow, and higher resistance limits the flow.

Ohm’s Law

Ohm’s law states that V = IR, V being voltage in volts, I being the current in amps, and R being the resistance in Ohms. This equation describes the relation of current, voltage, and resistance in conductivity in almost all electrically conductive objects (objects that don’t adhere to this law are known as non-ohmic materials, such as semiconductors)

Circuits

Circuits are full loops that allow the flow of electrons and electricity to be transferred from one place to another. We explored this with our online simulator that showed you how to create circuits. Open circuits (a gap somewhere within your loop) prevent your flow & stop it somewhere, and closed circuits allow the flow.

Example Problem: Which resistor do we need?

Ohm’s law is very useful when putting together electronics and staying safe. Let’s say you have a 9 volt battery. The recommended current for an LED (Light Emitting Diode) is 18 milliAmps (mA) or .018 Amps. What resistor should the circuit use?

Answer:

Using V=IR, we find that R = 500 Ohms. Using a 500 Ohm resistor in our circuit will prevent too much current from entering the LED and damaging it.

Types of Electrical Components

Wires

Wires conduct electricity, and connect together the different electrical components in a circuit, to make sure the energy flows throughout the entire system. The higher the amperage, the bigger the wire needs to be, because all wires have resistance, which will convert the electron flow into heat.

Switches/Buttons

Switches open and close a circuit, and can turn off the flow of electricity. There are two types of switches: momentary and latching. A momentary switch is like a button press, and will release if you let go. Latching switches stay in the position they move to, like a light switch. Within switches, there are different ways they can operate (single pull, single throw)

Voltage Sources

You need a voltage source in a circuit to push electrons through wires. Most common are batteries. Different voltage and different maximum current output. Measured in Amps per hour. Stacking more batteries will increase the voltage. Putting batteries next to each other will increase the current.

Resistor

Resistors provide resistance to the flow of electricity. Made of poor conductors such as carbon, provide different levels of heat resistance. Band code will show how much resistance each resistor will have. Measured in ohms.

Variable Resistors / Potentiometers

Variable resistor: used in volume control, or controlling a light. Works by having a wiper rotate along a resistor strip; the more distance between the wiper and the voltage source, the more resistance there will be.

Adding Resistors

Resistors connected in a series (in a line) vs parallel (electricity flows through at the same time)

Please watch our meeting recording (starting from 18:36 to 28:56) to view some example resistor problems, and see how to use them in an actual circuit!

Resistor Formulas

Total resistance in series: Sum of individual resistances

Total resistance in parallel: add all the reciprocals of resistors, then take the reciprocal of that value.

Capacitors

Capacitors temporarily store a charge on them. The amount of capacitance they have is measured using the formula q=CV, where q is the amount of charge they can store, C is the capacitance and V is the voltage.

Diodes / LEDs

Diodes only allow electricity to flow in 1 direction. They also create a nearly constant voltage drop. LED’s (Light Emitting Diodes) are diodes that produce light.

Transistors

Transistors are used as switches for electrical components. In a transistor, there are 3 connections, Source/Collector, Gate/Base, and Drain/Emitter. A voltage is applied to the source. If another lower voltage than the source is provided to the gate, the voltage applied at the source will be able to flow through to the drain. This means that transistors can be used to control higher currents / voltages. For example, transistors can be used to allow a device that uses 3.3 volt logic to control devices with 5 volt logic.

Integrated Circuits

Integrated circuits are a way of combining multiple electrical components into one, compact piece. Integrated circuits vary in size and complexity and have many different functions

How can we express circuits?

We can express circuit diagrams using symbols. These symbols make it easier for other people to replicate circuits or figure out how they work. There are many different diagram styles and standards, but many of the most basic components will be very similar on all circuit diagrams.

Breadboards

Breadboards make it easy to prototype with electrical components. Many electrical components work directly with breadboards and they allow you to easily connect components and build circuits.without soldering or complex wiring.

Summary

We know we just went over a lot of information but, trust us, it will all be important later on! In the next few meetings, we will be exploring applying these electrical knowledge to create actual IoT devices… stay tuned!