Lab 01
There is a pre-lab that needs to be in advance to prepare for this lab! Instructions on how to make your Github Repo, etc. are there.
For this assignment, you are going to
C) Blink a LED using the Arduino
F) Frankenlight
For the report, make a copy of this wiki page for your own repository, and then delete everything but the headers and the sections between the stars. Write the answers to the questions under the starred sentences. Include snippets of code that explain what you did.
Deliverables are due next Tuesday. Post a link to the wiki page on your main class hub page.
For this lab, we'll be using the Adafruit Metro Mini development board as our hardware platform. This board is a derivative of the Arduino UNO R3.
You should have already have installed the Arduino software on your laptop.
Wire the power rails of your breadboard so that the red rails are connected to the +5V pin of the Metro Mini, and the blue or black rails are connected to the GND pin.
Include a picture of your own breadboard in the report. (We trust you to plug the Metro Mini and wires in properly. This is really practice for including images in your reports.)
a. What color stripes are on a 220 Ohm resistor? With the Arduino unplugged, build the circuit below. You can use any color LED.
If you need a diagram of what this looks like on your board, here's a hint
If your button doesn’t work, check that it’s oriented as shown below. You might need to rotate it by 90 degrees.
A typical pushbutton, when pressed, connects the 2 pins on one side to the 2 pins on the other side. a. What color stripes are on a 220 Ohm resistor?
Connect the Metro Mini to your computer using the USB cable. The green LED on top of the Arduino should light.
Does your LED light? Why not? What do you have to do to light the LED?
b. What do you have to do to light your LED?
(Do not deconstruct what you have set up on your breadboard until you find it necessary! For instance, don't undo the LED and button setup that you did in Part B when you start doing Part C.)
Arduino boards typically come preloaded with a version of the Blink program on it. This code lets its L LED (connected on pin 13) blink as soon as the USB cable starts powering the board. Let us modify that program.
Launch the Arduino application on your computer. It will open to the template of a new empty sketch. Here is what it looks like:
Check out the Blink example code: File->Examples->Basics->Blink.
a. What line(s) of code do you need to change to make the LED blink (like, at all)?
b. What line(s) of code do you need to change to change the rate of blinking?
c. What circuit element would you want to add to protect the board and external LED?
To compile and upload your code, take the following steps (note that 1, 2 should only have to be done once):
- In the Arduino IDE, select the board we are using: Tools -> Board -> Arduino/Genuino UNO
- You may also have to select a communications (or COM) port (Tools -> Port -> Serial Port). The port should be something like
/dev/cu.SLCA_USBtoUART(on MAC)/dev/ttyUSB0(on Linux), orCOM3(on Windows, could be another number). If they are not showing up, make sure you've installed the SiLabs CP210x drivers. - To compile your code, click on the "checkmark" on the upper far left of the Arduino development window.
- To upload compiled code to the Arduino, click on "right arrow" besides the "checkmark."
- When the code is uploaded, the Arduino should automatically start running your new code.
Change the delay parameter to modify blink rate of your LED to make it blink faster.
d. At what delay can you no longer perceive the LED blinking? (And how can you prove to yourself that it is, in fact, still blinking?
Modify the code to make your LED blink your way.
e. Save your new blink code to your lab 1 repository, with a link on the Lab report wiki page.
Now modify the circuit and program so that you can blink an external LED on pin 9.
Make a video of your LED blinking, and add it to your lab submission.
Set up the following circuit, and try making the LED glow brighter and dimmer.
a. Are you able to get the LED to glow the whole turning range of the potentiometer? Why or why not?
The Arduino cannot output an analog voltage, only 0 or 5Vs. So how can we fade an LED using the Arduino?
The fading light is done using pulse width modulation, or PWM. The LED is toggled on and off very quickly: say, 1,000 times per second. Much faster than your eye can follow.
The percentage of time that the LED is on (called the duty cycle) controls its apparent brightness.
Update your circuit so the jumper wire connects to pin 11. (To control an LED using PWM, you have to connect it to one of the pins that supports PWM (not all do!).
Here's a hint diagram if you need it.
On your computer, in the Arduino IDE, open the Fade sketch (File > Examples > 01.Basics > Fade ).
Look at the code.
a. What do you have to modify to make the code control the circuit you've built on your breadboard?
b. What is analogWrite()? How is that different than digitalWrite()?
Now upload your sketch and check that the LED fades on and off. Try changing a few parameters to make your own funky lighting pattern.
For this part of lab, you get to hack apart an existing electronic device.
1. Take apart your electronic device, and, as well as you can, draw a system diagram of what is inside.
a. Is there computation in your device? Where is it? What do you think is happening inside the "computer?"
b. Are there sensors on your device? How do they work? How is the sensed information conveyed to other portions of the device?
c. How is the device powered? Is there any transformation or regulation of the power? How is that done? What voltages are used throughout the system?
d. Is information stored in your device? Where? How?
2. Using your diagram, figure out where a good point would be to hijack your device and implant an LED.
(Alternately, you can hijack a light or other display on the device using an extra button.)
We have perfboards in the lab, which provide a handy way to connect your parts. You may want to make your light using passive components (such as switches, resistors or potentiometers) rather than your microcontroller (also known as a μC), unless you think of a nice way to incorporate the μC into your design without soldering it inside of a light. (You'll need it back for future labs and projects!) If your design does require a μC, perhaps you can run a lead from your breadboard to the main light, although you'll lose portability that way. Clever use of components is encouraged!
Make a video showing off your Frankenlight.
Include any diagrams or photos in your lab write-up.
The best Frankenlight will win course-wide fame and glory.
Super awesome circuit schematics by David Sirkin. Thanks David!