Experiment Guide for the SparkFun Tinker Kit
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D___Run___ Experiment 4: Driving Multiple LEDs
Introduction
Now that you've gotten your LED to blink on and off, it's time to up the stakes a little bit – by connecting six LEDs at once. We'll also give your RedBoard a little test by creating various lighting sequences. This experiment is a great setup to start practicing writing your own programs and getting a feel for the way your RedBoard works.
Along with controlling the LEDs, you’ll learn a few programming tricks that keep your code neat and tidy!
You will need the following parts:
- 1x Breadboard
- 1x SparkFun RedBoard
- 6x LEDs
- 6x 330Ω Resistors
- 7x Jumper Wires
Didn't Get the Tinker Kit?
If you are conducting this experiment and didn't get the Tinker Kit, we suggest using these parts:
Hardware Hookup
Ready to start hooking everything up? Check out the wiring diagram and hookup table below to see how everything is connected.
| Polarized Components | Pay special attention to the component’s markings indicating how to place it on the breadboard. Polarized components can only be connected to a circuit in one direction. |
Wiring Diagram for the Experiment
Open the Sketch
Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit.
You can type out or copy and paste the following code into the Arduino IDE. Hit upload, and see what happens!
language:cpp
/*
SparkFun Tinker Kit
Example sketch 04
MULTIPLE LEDs
Make six LEDs dance. Dance LEDs, dance!
This sketch was written by SparkFun Electronics,
with lots of help from the Arduino community.
This code is completely free for any use.
Visit http://learn.sparkfun.com/products/2 for SIK information.
Visit http://www.arduino.cc to learn more about Arduino.
*/
// To keep track of all the LED pins, we'll use an "array."
// An array lets you store a group of variables, and refer to them
// by their position, or "index." Here we're creating an array of
// six integers, and initializing them to a set of values:
int ledPins[] = {4,5,6,7,8,9};
void setup()
{
//create a local variable to store the index of which pin we want to control
int index;
// For the for() loop below, these are the three statements:
// 1. index = 0; Before starting, make index = 0.
// 2. index <= 5; If index is less or equal to 5, run the following code
// 3. index++ Putting "++" after a variable means "add one to it".
// When the test in statement 2 is finally false, the sketch
// will continue.
// This for() loop will make index = 0, then run the pinMode()
// statement within the brackets. It will then do the same thing
// for index = 2, index = 3, etc. all the way to index = 5.
for(index = 0; index <= 5; index++)
{
pinMode(ledPins[index],OUTPUT);
}
}
void loop()
{
// This loop() calls functions that we've written further below.
// We've disabled some of these by commenting them out (putting
// "//" in front of them). To try different LED displays, remove
// the "//" in front of the ones you'd like to run, and add "//"
// in front of those you don't to comment out (and disable) those
// lines.
// Light up all the LEDs in turn
oneAfterAnotherNoLoop();
// Same as oneAfterAnotherNoLoop, but less typing
//oneAfterAnotherLoop();
// Turn on one LED at a time, scrolling down the line
//oneOnAtATime();
// Light the LEDs middle to the edges
//pingPong();
// Chase lights like you see on signs
//marquee();
// Blink LEDs randomly
//randomLED();
}
/*
oneAfterAnotherNoLoop()
This function will light one LED, delay for delayTime, then light
the next LED, and repeat until all the LEDs are on. It will then
turn them off in the reverse order.
*/
void oneAfterAnotherNoLoop()
{
// time (milliseconds) to pause between LEDs
int delayTime = 100;
// turn all the LEDs on:
digitalWrite(ledPins[0], HIGH); //Turns on LED #0 (pin 4)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[1], HIGH); //Turns on LED #1 (pin 5)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[2], HIGH); //Turns on LED #2 (pin 6)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[3], HIGH); //Turns on LED #3 (pin 7)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[4], HIGH); //Turns on LED #4 (pin 8)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[5], HIGH); //Turns on LED #5 (pin 9)
delay(delayTime); //wait delayTime milliseconds
// turn all the LEDs off:
digitalWrite(ledPins[5], LOW); //Turn off LED #5 (pin 9)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[4], LOW); //Turn off LED #4 (pin 8)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[3], LOW); //Turn off LED #3 (pin 7)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[2], LOW); //Turn off LED #2 (pin 6)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[1], LOW); //Turn off LED #1 (pin 5)
delay(delayTime); //wait delayTime milliseconds
digitalWrite(ledPins[0], LOW); //Turn off LED #0 (pin 4)
delay(delayTime); //wait delayTime milliseconds
}
/*
oneAfterAnotherLoop()
This function does exactly the same thing as oneAfterAnotherNoLoop(),
but it takes advantage of for() loops and the array to do it with
much less typing.
*/
void oneAfterAnotherLoop()
{
int index;
int delayTime = 100; // milliseconds to pause between LEDs
// make this smaller for faster switching
// Turn all the LEDs on:
// This for() loop will step index from 0 to 5
// (putting "++" after a variable means add one to it)
// and will then use digitalWrite() to turn that LED on.
for(index = 0; index <= 5; index++)
{
digitalWrite(ledPins[index], HIGH);
delay(delayTime);
}
// Turn all the LEDs off:
// This for() loop will step index from 5 to 0
// (putting "--" after a variable means subtract one from it)
// and will then use digitalWrite() to turn that LED off.
for(index = 5; index >= 0; index--)
{
digitalWrite(ledPins[index], LOW);
delay(delayTime);
}
}
/*
oneOnAtATime()
This function will step through the LEDs,
lighting only one at at time.
*/
void oneOnAtATime()
{
int index;
int delayTime = 100; // milliseconds to pause between LEDs
// make this smaller for faster switching
// step through the LEDs, from 0 to 5
for(index = 0; index <= 5; index++)
{
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(delayTime); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
}
/*
pingPong()
This function will step through the LEDs,
lighting one at at time in both directions.
*/
void pingPong()
{
int index;
int delayTime = 100; // milliseconds to pause between LEDs
// make this smaller for faster switching
// step through the LEDs, from 0 to 5
for(index = 0; index <= 5; index++)
{
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(delayTime); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
// step through the LEDs, from 5 to 0
for(index = 5; index >= 0; index--)
{
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(delayTime); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
}
/*
marquee()
This function will mimic "chase lights" like those around signs.
*/
void marquee()
{
int index;
int delayTime = 200; // milliseconds to pause between LEDs
// Make this smaller for faster switching
// Step through the first four LEDs
// (We'll light up one in the lower 3 and one in the upper 3)
for(index = 0; index <= 2; index++) // Step from 0 to 3
{
digitalWrite(ledPins[index], HIGH); // Turn a LED on
digitalWrite(ledPins[index+3], HIGH); // Skip four, and turn that LED on
delay(delayTime); // Pause to slow down the sequence
digitalWrite(ledPins[index], LOW); // Turn the LED off
digitalWrite(ledPins[index+3], LOW); // Skip four, and turn that LED off
}
}
/*
randomLED()
This function will turn on random LEDs. Can you modify it so it
also lights them for random times?
*/
void randomLED()
{
int index;
int delayTime;
// The random() function will return a semi-random number each
// time it is called. See http://arduino.cc/en/Reference/Random
// for tips on how to make random() even more random.
index = random(5); // pick a random number between 0 and 5
delayTime = 100;
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(delayTime); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
Code to Note
int ledPins[] = {4,5,6,7,8,9};
When you have to manage a lot of variables, an "array" is a handy way to group them together. Here we're creating an array of integers, called ledPins, with six elements. Each element is referenced by its index. The first element is the index of [0].
digitalWrite(ledPins[0], HIGH);
You refer to the elements in an array by their position. The first element is at position 0, the second is at position 1, etc. You refer to an element using "ledPins[x]" where x is the position. Here we're making digital pin 4 HIGH, since the array element at position 0 is "4."
index = random(5);
Computers like to do the same things each time they run. But sometimes you want to do things randomly, such as simulating the roll of a dice. The random() function is a great way to do this.
See http://arduino.cc/en/reference/random for more information.
What You Should See
This is similar to Experiment 1, but instead of one LED, you should see all the LEDs blink. If they don't, make sure you have assembled the circuit correctly and verified and uploaded the code to your board, or see the Troubleshooting section.
Troubleshooting
Some LEDs Fail to Light
It is easy to insert an LED backward. Check the LEDs that aren't working and ensure they are in the correct orientation.
Operating out of Sequence
With eight wires it's easy to cross a couple. Double check that the first LED is plugged into pin 4 and each pin thereafter.
Starting Fresh
It’s easy to accidentally misplace a wire without noticing. Pulling everything out and starting with a fresh slate is often easier than trying to track down the problem.