Circuits Lab Introduction ENGR 1181 Circuits Lab Introduction Lab 3 Engineering Education Innovation Center

Lab Safety Lab Rules Closed Toed Shoes No food or drink ENGR 1181 Lab Safety Lab Rules Closed Toed Shoes No food or drink Instructor/TA checking before testing Turning off/on Breadboard Checkout Sheet Signed Although it is the third lab, lab rules should be reinforced to help students be safe. Wearing closed toed shoes prevents injuries where pieces of lab equipment may fall onto the floor. Food or drink could potentially cause damage to the electrical equipment or nearby computers. Signing checkout sheets helps to ensure a quick transition between classes and makes the class more enjoyable for everyone. Additionally, it is part of the grade and not having it signed will result in a penalty. Some additional rules that are particular to this lab are listed as well: -An instructor or TA should check their circuit before running it to both ensure that they have done it correctly and should receive accurate data, as well as to avoid any instances where components have been inserted incorrectly (i.e blowing up the LEDs by not putting on a resistor) -The same can be said for turning the breadboard on and off as components are moved or added.

Task 1: Basic Setup (Step 1) Connect 5V power supply to the toggle switch box by plugging in the black wire Next connect the red and black wires originating from the bread board sockets to their appropriate positions as shown: 5 V power supply Notice Red and Black wires connecting from +5V and Ground Posts. Make sure metal part of wires are touching metal posts. Instructor notes: Make sure that all wires are connected as shown and the including two short Orange wires P. 3

Task 1: Basic Setup (Step 2) Connect the red and black probes to their appropriate Digital Multimeter (DMM) connections as shown in the figure below : Turn the DMM dial to the DCV setting to configure it as a voltmeter This is the standard configuration of Leads Created 7/19/10 to incorporate new voltmeter – R.C.Busick Mention the fact that once the AC adapter is plugged in, the upper horizontal row connected through a red wire on the bread board would be @ 5V (positive end) And the lower Horizontal row connected through the black wire would be @ ground. This would be helpful for tasks 3 and 4. P. 4

Converting from Schematic to Physical ENGR 1181 Converting from Schematic to Physical Follow the Diagram Schematic Physical Layout +5 Volts +5 Volts +5 Volts +5 Volts Ground Ground Ground This slide is meant to help students see the connection between the circuit schematic and what it will look like on their breadboards. A good way of explaining it is to start at the red terminal on the board, and the positive end of the battery on the schematic. From there, connections are made between components (the resistor) and back to the battery (also called the ground). Note that it is helpful to have the power source and ground be attached to the horizontal sections, but it can be done several ways. Additionally, reiterate that the resistor and wires span the gaps in order to complete the circuit and avoid a short circuit. Circuit Schematic

Task 3: Series Circuit, (Step 1) Toggle off power to board. Place the nominally valued 200 and 300 Ohm resistors on the Breadboard, as shown in the schematic and in the picture (right). NOTE: Vertical location of resistors is critical. Circuit Schematic 2 By now the students should know how to set the DMM as an ohmmeter and the fact that red wire corresponds to +5V and black corresponds to ground. The picture does not clearly tell where the red and black wires are coming from 3 P. 6

An Equivalent Circuit Different physical circuits can correspond to same logical circuit An example of the same circuit in a different physical layout P. 7

Under side of Bread board Do you now understand the concept of metal strips?

Common Problems Misaligning resistors and wires ENGR 1181 Common Problems Misaligning resistors and wires Not using calculated values for resistances Not adding a resistor within the LED Circuit Miscalculations The most often reason for an incorrect circuit is the misalignment of wires and resistors. This is quite common as it is very easy to believe you have everything hooked up correctly only to find out that a resistor or wire is in the incorrect column Students are asked to determine the value of the resistors as the first step of the lab, and they should use these values for the rest of the calculations. Without a series limiting resistor, the LED will overload and break permanently. Stress that students ought to at least try some of the calculations in class if they have time. The equations are not complicated, but since there are so many of them, it can be difficult to get them started and identify what needs to be found.

More Common Problems The power strip isn’t on Ground the circuit 3) LED are placed backwards (Short lead to ground) 4) Halves of the boards aren’t being bridged 5) Wires are missing from the main 5V power source *Never measure CURRENT using the DMM. The current should always be calculated from measured voltage and resistance values.

Two - Person Teams Perform this lab in teams of 2 people. ENGR 1181 Two - Person Teams Perform this lab in teams of 2 people. If there are only 3 people, all can work together. Record results in provided calculation sheet and perform calculations.

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