Using Your Arduino Breadboard and Multimeter Work in

Using Your Arduino, Breadboard and Multimeter Work in teams of two! ME 120 Fall 2013

Your Multimeter pincer clips – good for working with breadboard wiring probes (push these onto probes) leads Turn knob to select the type of measurement. You will use the multimeter to understand troubleshoot circuits, mostly measuring DC voltage, resistance and DC current.

The Arduino Uno Power can be provided through the USB cable (+5 V from the computer) or externally (7 -12 V supply recommended)

The Sparkfun Redboard (Uno) Power can be provided through the USB cable (+5 V from the computer) or externally (7 -12 V supply recommended)

Measure Vin is the voltage of the power supply. The USB supplies a nominal 5 V (4. 43 V was measured when this photo was taken)

Change power source and measure Vin In this photo, a 7 V DC power supply was plugged into the power jack of the Arduino.

Check Voltage at 5 V Power Pin The on-board voltage regulator maintains the voltage on the 5 V pin at about 5 V The measured voltage is close to 5 V target.

Check Voltage at 3. 3 V Pin The FIDI chip on the Arduino, which helps the microcontroller talk with your computer through the USB cable, also has an on-board voltage regulator that outputs 3. 3 V. If you need less than 5 V for a project, you can use the 3. 3 V pin, Which provides about 3. 3 V. The current draw from the 3 V 3 pin is limited to 50 m. A. max power = V∙I = 3. 3 V∙ 0. 05 A = 0. 165 W = 165 m. W

Select Resistors Find the 330 W and the 10 k. W resistors from your parts kit. color digit black 0 brown 1 red 2 orange 3 yellow 4 green 5 blue 6 violet 7 gray 8 white 9 first digit second digit tolerance gold = ± 5% silver = ± 20% number of zeros Example: 330 W resistor: 3 = orange Add 1 zero to 33 to make 330, so 1 = brown So, 330 = orange, brown Now, find the 10 k. W resistor.

Check Resistance of Resistors

Building a circuit on a breadboard

Voltage Drops Around Closed Loops + - 5 V

Select Resistors Find the 10 k. W and the 330 W resistors from your parts kit. color digit black 0 brown 1 red 2 first digit second digit tolerance gold = ± 5% silver = ± 20% number of zeros orange 3 yellow 4 green 5 blue 6 violet 7 1 = brown 0 = black Add 3 zeros, so 3 = orange gray 8 So, 10 kΩ = brown black orange white 9 Example: 10 k. W resistor Now, find the 330 W resistor. 13

Build the Series Circuit Below 5 V 10 k. W 330 W + - 5 V 330 W 10 k. W + 5 V All of these circuits are the SAME!! - 330 W 14

Compute Voltage Drops Across the Two Resistors Use Ohm’s Law: V=I·R Given R 1 = 10 kΩ R 2 = 330 Ω Vb = 5 V Compute the equivalent resistance Req = _______ Ω Compute the current I = _______ A Compute the voltage drop across R 1 ∆VR 1= _______ V Compute the voltage drop across R 2 ∆VR 2= _______ V Add up the voltage drops across the resistors with the Negative voltage drop (the voltage rise) across the battery ∆VR 1 + ∆VR 2 – ∆Vb = ____ 15

Use Multimeter to Measure Voltages Around Loop 10 k. W (1) Across the 10 kΩ resistor ∆VR 1 = _____ + 5 V - 330 W (2) Across the 330Ω resistor ∆VR 2 = _____ (3) From GND to 5 V pin (same +/– direction that was used across the resistors ∆Vb = ____ (4) Add up the voltages ∆VR 1 + ∆VR 2 – ∆Vb = _______ 16

Compare Measurements to Theory R 1 = 10 k. W DVR 1 = 4. 84 V + Vb=5 V - R 2 = 330 W DVR 2 = 0. 16 V 4. 84 V + 0. 16 V – 5. 01 V = 0. 01 V Pretty close! 17

Kirchoff’s Voltage Law (KVL) Kirchoff’s Voltage Law says that the algebraic sum of voltages around any closed loop in a circuit is zero – we see that this is true for our circuit. It is also true for very complex circuits. R 1 = 10 k. W DV = 4. 84 V + 0. 16 V – 5. 01 V ≈ 0 - DV = 0. 16 V R 2 = 3300 W Notice that the 5 V is DIVIDED between the two resistors, with the larger voltage drop occurring across the larger resistor. 18

Gustav Kirchoff (1824 – 1887) was a German physicist who made fundamental contributions to the understanding of electrical circuits and to the science of emission spectroscopy. He showed that when elements were heated to incandescence, they produce a characteristic signature allowing them to be identified. He wrote the laws for closed electric circuits in 1845 when he was a 21 year-old student. Photo: Library of Congress 19