Using the Board of Education Breadboard and Your Multimeter ENGR 120 Work in teams of two!

Your Multimeter leads probes pincer clips – good for working with Boe-Bot wiring You will use the multimeter to understand and troubleshoot circuits, mostly measuring DC voltage, resistance and DC current. turn knob to what you would like to measure (push these onto probes)

Measure V in Vin will be the same as your power supply voltage. For the case below, 4 AA batteries are used resulting in approximately 6 V (5.79 V to be more exact). Vin = power supply voltageVss = ground (negative side of battery) Switch to DC Volts

Measure Vdd Vdd will always be around 5V (it is 4.94 V here). A voltage regulator on the Board of Education reduces this voltage from Vin down to ~ 5V. The Boe-Bot operates on 5V DC. Vdd ~ 5VVss = ground (negative side of battery)

Select Resistors Find the 470  and the 10k  resistors from your Boe-Bot kit. Example: 470  resistor: 4 = yellow 7 = violet Add 1 zero to 47 to make 470, so 1 = brown Now, find the 10k  resistor. So, 470 = yellow, violet, brown Diagram from the Parallax Robotics book

set multimeter to measure  R ~ 470  Check Resistance of Resistors

Connecting an LED Electricity can only flow one way through an LED (or any diode). LED = Light Emitting Diode Diagram from the Parallax Robotics book

Building an LED Circuit Vdd = 5V These circuit diagrams are equivalent these holes are “connected” Vdd = LED holes in this direction are not connected Diagram from the Parallax Robotics book

Replace the 470  Resistor with the 10k  Resistor What happens and Why?? ANSWER: The smaller resistor (470  ) provides less resistance to current than the larger resistor (10k  ). Since more current passes through the smaller resistor, more current also passes through the LED making it brighter. What would happen if you forgot to put in a resistor? You would probably burn up your LED.

Connect the Resistor to Pin 12 (P12) ' {$STAMP BS2} ' {$PBASIC 2.5} DO HIGH 12 PAUSE 500 LOW 12 PAUSE 500 LOOP Enter and run the following PBASIC program: Diagram from the Parallax Robotics book

Causes pin 12 to output a constant 5V (Vdd) ' {$STAMP BS2} ' {$PBASIC 2.5} DO HIGH 12 PAUSE 500 LOW 12 PAUSE 500 LOOP How the Program Works infinite loop Causes pin 12 to output a constant 0V (Vss) HIGH = 5V and LOW = 0V (Always!!!!) wait 500 ms Wait 500 ms Diagram from the Parallax Robotics book

Now Experiment on Your Own! (1)Try changing the time to 1.5 seconds on and 1 second off (2)Connect the resistor to pin 8 and change the program to match (3)Blink out SOS in Morse code (dot-dot-dot-dash-dash-dash-dot-dot-dot) a.three short pulses (0.25 seconds each) followed by... b.three long pulses (0.75 second each) followed by... c.three short pulses (0.25 seconds each) followed by... d.a brief pause (1 second) e.repeat a through d using an infinite loop Show your instructor when you have completed exercise (3).

' {$STAMP BS2} ' {$PBASIC 2.5} DO PULSOUT 12, PAUSE 2000 LOOP Enter and run the following PBASIC program: Another Way to Make the LED Blink Causes pin 12 to output a constant 5V for x 2  s =  s = 0.13 s Wait 2000 ms = 2 s Diagram from the Parallax Robotics book

Find the PULSOUT Command Using PBASIC Help Now, you change the program to make the LED blink on for a duration of 0.01 seconds and off for a duration of 0.1 seconds. Show your instructor.

The End