Introduction

I bet we all love holidays. Christmas is my favorite holiday of the year. We love Christmas because we get to travel to our hometowns, spend time with loved ones and eat lots of delicious foods…..but what I like about Christmas is the decorations; the colorful ribbons, flowers, balloons and my favorite… the Christmas running lights. With these lights put up in our homes, shops, supermarkets, malls and public places, they are very eye catching and mind blowing as they run around in different patterns.  

Christmas running lights also known as LED chasers are built in such a way that multiple LEDs flash on and off for a period of time, forming different patterns such as scrolling, dimming and when looked carefully, they look like they are chasing each other in one direction.

Now that you know about running lights, where else can we utilize  them for decoration?

In this lesson you will learn:

1. More about LEDs
2. How to connect multiple LEDs
3. Digital loops

Important things to learn

    a)More about LEDs

From UNDA project 1, we learnt how LEDs work and how to connect them. In this project, we will learn how to connect multiple LEDs. 

But first, a bit more about LEDs.

LEDs come in different shapes, colors, sizes and  brightness. The different characteristics allow you to use them for different purposes e.g. How big or small do you want your LEDs to be.

Size

LEDs are available in different sizes. The most common  sizes are 3mm, 5mm, 8mm and 10mm. The size refers to the outside diameter of the LED. 5mm LED is the standard and most common LED. 3mm LED is the smallest and great for  use in small fitting projects while 8mm and 10mm LEDs are best for bright projects.

Shape

LEDs also come in different shapes. Common shapes include flat, dome, cylindrical and round shape. They are used in different applications for different purposes example a dome shaped LED helps reflect light out of the top, the round one reflects light out uniformly while the rectangular shape is great for side viewing.

Colors

Light emitting diodes are available in a wide range of colors. The most common ones being red, orange, green, yellow, blue and white

In this project, we will use the common 5mm round in shape LEDs with different colors that is red, blue, green, orange and clear.  

  b)Connecting multiple LEDs 

Can you recall how to connect a single LED from UNDA project 1

For multiple LEDs, the circuit is a bit different but the same rules apply. To connect our multiple LEDs, we connect each LED to a battery power supply through a resistor as in the diagram below. 

To switch the multiple LEDs ON and OFF repeatedly, we connect the LEDs to multiple pins on the Unda.Make to send on and off instructions. 

What instructions will be sent from the computer?

 For the multiple LEDs to turn on and off, the computer will send instruction to each LED that is;

Turn on red LED 
Wait 
Switch off red LED
wait 
Turn on yellow LED 
Wait 
Switch off yellow LED 
Wait
Switch on blue LED 
Wait
Switch off blue LED 
wait
Continue until LED green is turned on and off then repeats again to red LED 
The instructions can repeat for a number of times or continue endlessly.

And we are lucky, because unlike human beings, a computer never gets tired or bored and can keep doing a certain task no matter how many times you tell it. For us to give a computer instruction, we have to write the instruction in form of a program, however since we do not have the energy for repetitive tasks like a computer, to save us valuable energy and time we use something called a loop.

c. Digital Loops

First, what is a loop?

A loop just like the name suggests is going round and round and when you get to the starting point you go again and again.

When you need to repeat the same instruction again and again, we use a loop. Like in our diagram example below, if you want to give your friends a dance move instruction, you can tell them to repeat for a number of times instead of you repeating the instruction.

In UNDA project 1, we learnt that a computer sends digital instructions of 1’s and 0’s that is ON and OFF. 

Hence, a  digital loop is an ON(1) and OFF(0) instruction that repeats again and again. In our running lights project, the LEDs will turn on and off and repeat again and again.

Quiz