Using Your Arduino, Breadboard and Multimeter ME 120 Fall 2013 Work in teams of two!
Your Multimeter leads probes pincer clips – good for working with breadboard wiring You will use the multimeter to understand and troubleshoot circuits, mostly measuring DC voltage, resistance and DC current. Turn knob to select the type of measurement. (push these onto probes)
The Arduino Uno Power can be provided through the USB cable (+5V from the computer) or externally (7-12V supply recommended)
The Sparkfun Redboard (Uno) Power can be provided through the USB cable (+5V from the computer) or externally (7-12V supply recommended)
Measure V in Vin is the voltage of the power supply. The USB supplies a nominal 5V (4.43V was measured when this photo was taken)
Change power source and measure Vin In this photo, a 7V DC power supply was plugged into the power jack of the Arduino.
Check Voltage at 5V Power Pin The on-board voltage regulator maintains the voltage on the 5V pin at about 5V The measured voltage is close to 5V target.
Check Voltage at 3.3V 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 3.3V. If you need less than 5V for a project, you can use the 3.3V pin, Which provides about 3.3V. The current draw from the 3V3 pin is limited to 50mA. max power = V∙I = 3.3V∙0.05A = 0.165W = 165mW
Select Resistors Find the 330 and the 10k resistors from your parts kit. Now, find the 10k resistor. Example: 330 resistor: 3 = orange Add 1 zero to 33 to make 330, so 1 = brown So, 330 = orange, orange, brown colordigit black0 brown1 red2 orange3 yellow4 green5 blue6 violet7 gray8 white9 first digit second digit number of zeros tolerance gold = ±5% silver = ±20%
Check Resistance of Resistors
Building a circuit on a breadboard
Voltage Drops Around Closed Loops 5V
Select Resistors Find the 10k and the 330 resistors from your parts kit. Now, find the 330 resistor. Example: 10k resistor 1 = brown 0 = black Add 3 zeros, so 3 = orange So, 10kΩ = brown black orange colordigit black0 brown1 red2 orange3 yellow4 green5 blue6 violet7 gray8 white9 first digit second digit number of zeros tolerance gold = ±5% silver = ±20% 13
Build the Series Circuit Below 14 5V 10k 330 5V k 330 All of these circuits are the SAME!! 5V 10k
Compute Voltage Drops Across the Two Resistors Use Ohm’s Law: V = I · R 15 Given Compute the equivalent resistance Compute the current Compute the voltage drop across R 1 Compute the voltage drop across R 2 R 1 = 10kΩ R 2 = 330 Ω V b = 5V R eq = _______ Ω I = _______ A ∆V R1 = _______ V ∆V R2 = _______ V Add up the voltage drops across the resistors with the Negative voltage drop (the voltage rise) across the battery ∆V R1 + ∆V R2 – ∆V b = ________
Use Multimeter to Measure Voltages Around Loop (3) From GND to 5V pin (same +/– direction that was used across the resistors (1) Across the 10kΩ resistor (2) Across the 330Ω resistor ∆V b = ________ 16 5V k 330 ∆V R1 + ∆V R2 – ∆V b = _______ ∆V R1 = _____ ∆V R2 = _____ (4) Add up the voltages
Compare Measurements to Theory 17 V R2 = 0.16V V R1 = 4.84V V b =5V +-+- R 1 = 10k R 2 = 330 4.84V V – 5.01V = 0.01V Pretty close!
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. Notice that the 5V is DIVIDED between the two resistors, with the larger voltage drop occurring across the larger resistor R 1 = 10k R 2 = 3300 V = 0.16V V = 4.84V 4.84V V – 5.01V ≈ 0
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