Lab 2.4 Arduinos, Resistors, and Circuits

Transcription

1 Lab 2.4 Arduinos, Resistors, and Circuits Objectives: Investigate resistors in series and parallel and Kirchoff s Law through hands-on learning Get experience using an Arduino hat you need: Arduino Kit: (3) 10kΩ resistors, breadboard, RedBoard (or UNO), USB cable, LEDs, jumper wires Multimeter Online orksheet Laptop Task 1. Use an Arduino and Breadboard to Examine Resistors in Series and Parallel Resistor Colorband Chart Use this chart to help you identify your resistors. Breadboard Review Our breadboards have horizontally connected rows, and power rails that run vertically along the sides. Typically the (+) power rail is connected to power in your board and the (-) power rail to ground (GND). Horizontal rows are separated by a ravine, so the left and right side of each row is not connected. Notice the left power rails are not connected to the right power rails. The numbers and letters marked on various rows and columns don t serve any purpose other than to help guide you when building your circuit. Page 1 of 6

2 Resistors in Series Using your breadboard, place one 10kΩ resistor as indicated in the figure and measure with a multimeter. Yes, it should say ~10kΩ. Place another one in similar fashion but with a lead from each resistor connecting electrically through the breadboard and measure again. The meter should now say something close to 20kΩ. Try with a third resistor in series. Record your results. You may notice that the resistance you measure might not be exactly what the resistor says it should be. Resistors have a certain amount of tolerance, which means they can be off by a certain percentage. Thus, you may read 9.8Ω or 10.1kΩ. Resistor Configuration - Series Calculated Resistance Measured Resistance 10 kω 10 kω + 10 kω 10 kω + 10 kω + 10 kω LIGHT UP AN LED Place an LED lightbulb in your breadboard. Use a wire to connect the long leg of your LED to the 5 Volt channel on your Arduino. Use another wire to connect the short leg of your LED to top leg of your top resistor. Use a third wire to connect the bottom leg of the bottom resistor to the GND terminal on your redboard. If you haven t already, plug the usb cable into your Board and the other end into your laptop. Your LED should light up. Move the wire so the circuit is going across just two resistors, or just one resistor and observe the changes in the brightness of the LED. An LED is a Light Emitting Diode. Diodes allow current flow only in one direction. The long lead is the positive side of the device. Most components are diodes with a positive side labeled. ire your circuits properly. Diodes can t be reversed. You need to use a resistance of at least 140 ohms to prevent LEDs from burning up. Page 2 of 6

3 Resistors in Parallel Now try resistors in a parallel configuration. Place one 10kΩ resistor in the breadboard as before. Place a second 10kΩ resistor next to the first, taking care that the leads of each resistor are in electrically connected rows. Calculate what the new value should be (hint: it s going to be 5kΩ). Repeat with 3. Parallel Calculated Resistance Measured Resistance ire your parallel resistors to your LED and record your findings Table 3. Online Concept Questions Adding additional resistors in series increases / decreases brightness of the LED Adding additional resistors in parallel increases / decreases brightness of the LED Page 3 of 6

4 Task 2: Investigate Kirchoff s Laws through Calculations and with your Arduino Use Kirchoff s Laws to Analyze the Circuit Below. Label your voltage loops and label resistors with + and -. I 1 I 3 I 2 Calculated Currents Enter these solutions into the online worksheet I 1 = I 2 = I 3 = After you calculate I 1, I 2, and I 3, build the Circuit on your Arduino (continued on next page) Page 4 of 6

5 Measure I 1, I 2, and I 3. Set the multimeter to ma. To measure current your multimeter needs to be in line with the circuit, acting as a wire in the circuit. You need to cut the circuit and connect one probe to each of the cut ends: Remove the breadboard end of the wire, hold one lead of the multimeter to the wire, and the other lead of the multimeter to the end of the resistor. Measured Currents I 1 = I 2 = I 3 = Compare your measured currents with the calculated currents. If there is any remaining time, work on your team project or build more fun Arduino circuits. Page 5 of 6