Lab 1 - The Circuit

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School

University of Massachusetts, Amherst *

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Course

152

Subject

Electrical Engineering

Date

Jan 9, 2024

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pdf

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Uploaded by ConstableMoon12743

Lab 1 - The Circuit Overview In this lab you will learn the basic techniques of constructing circuits and making measurements using the iOLab. Since many of the labs you will perform involve electrical circuits, you will need to understand how the iOLab can function as a power supply, a device that applies a voltage to a circuit, and a voltmeter and ammeter , devices that can measure the voltage and current at particular places in the circuit. Let’s begin by defining an electrical circuit . A circuit is literally a loop. An electrical circuit is a loop made of various electrical components like batteries, wires, resistors, light bulbs, capacitors, and diodes. Electrical circuits can comprise multiple loops interconnected in thousands of different ways. Of course it is always best to start with the simplest case of a single circuit. First you will need to connect some wires that come with the Electricity and Magnetism Accessory Pack. The wires are bundled together and you can simply peel the wires apart as needed. The wires typically have a pin end and an alligator clips end: The pin ends connect to the connection points on the iOLab or breadboard. The alligator clips can connect to different circuit elements or connect to each other to make wires longer. Now setup your iOLab device: 1

● Detach the dongle from the iOLab device and connect to a USB port on your computer. ● Launch the iOLab application installed on your computer. The dongle indicator at the top of the application window should be on. ● Check the Analog 7 in the list of Sensors along the left side of the application window. ● Turn on the power of the iOLab device. The remote indicator at the top of the application window should be on. ● Connect a wire to the 3.3V output of the iOLab device. Connect a second wire to the A7 input of the iOLab device. Your iOLab setup should look like this: 7 Part 1 - Breadboard Connections The breadboard has MANY holes and so an attempt to try every pairwise combination would be tedious. Instead of trying every pair of holes, you are asked to apply intelligence to the issue and try enough holes that the pattern of connections has become absolutely certain. Here is a video to show you how to test the breadboard connections. The breadboard in the video may differ from the one you have, BUT the concept of testing the connection is the same. Breadboard Connections ( https://youtu.be/ERCLlfAnSZ4 ) Remember: ● A measurement of 3.3V means the two points you test on the breadboard are connected. The circuit is closed. ● A measurement of 1.5V means the circuit is open and the two points NOT connected. The circuit is NOT closed. 1. Use the image of the breadboard below and draw lines across all holes you have determined to be connected. 2

Once you know which holes in the breadboard are connected to each other and which ones are not, we want to use the breadboard to construct circuits. The advantage of using a breadboard is it is easy to connect circuit elements together without soldering. Part 2 - Voltage and Voltmeters We build all kinds of circuits to do things. In our home and places of work there are lots of circuits to run the electronic devices we use everyday; to light the lights, power computers, TVs, etc. But all of these things need energy. Where does the energy come from? The energy that runs electronics comes from the electrical potential difference or voltage applied to the electronics. To see how that works, let’s look at what a voltage is, or better what the unit of voltage is. A voltage is measured in Volts (V): Right away you should recognize a Joule (J) is the SI unit of energy. A Coulomb (C) is the SI unit of electric charge, so a Volt is the energy per unit charge applied to the circuit. When charges in the circuit have energy, they make the circuit do the things it is supposed to do. The light bulb lights up or the speaker emits sound or music. Now let’s make a very simple circuit with a light emitting diode (LED). Your E&M accessory pack should have two LEDs; one red and one green. Take out the red LED: 3

The LED is polarized, which means it only works when the voltage is applied to it a certain way. Remember voltage is an electrical potential difference between two points in a circuit. If one potential is higher (+) than the other potential (-), then the voltage is positive. Notice on the LED one of the terminal wires is longer than the other. Also notice that at the base on the LED “bulb” is flattened. The longer terminal prefers to be connected in the circuit at the higher potential, while the terminal on the flattened side prefers the lower potential. Construct a circuit using the iOLab, alligator clip wires, breadboard, and red LED. ● Connect the red alligator clip wire between the high side (+) of the LED and 3.3V on the iOLab ● Connect the black alligator clip wire between the low side (-) of the LED and GND on the iOLab. Your circuit should like something like this: 4