Blink 2 - An S4A (Scratch for Arduino) Project using a Breadboard & an LED

This is version 2 of Blink, where we shall see how to use a solderless breadboard to connect an LED to the Arduino. Learning to use breadboards is very fundamental to building circuits. The S4A (Scratch for Arduino) code we shall use here is exactly the same as in the previous Blink project. And the exact same blink functionality for the LED will be developed, but using a different wiring this time involving a breadboard.

Why use a breadboard? A breadboard is a quick, easy way to prototype a circuit. It allows you to experiment with electronic circuits, build and test them without any soldering. It can be used to build the simplest of circuits to very complex ones. You can read more about breadboards here and here.

Back to Blink2... We shall connect the LED to Pin 13, just as we did in Blink version 1. The S4A code for blinking the LED turns it on and off, with an interval of 1 second, to provide the blinking effect.

Here's the wiring we shall use for Blink2 with the above S4A code:

As you can see from the image, the LED is placed on the breadboard this time, rather than connected directly to the board as in Blink version 1. We use a resistor to connect the positive leg to Pin 13. The negative leg is connected to the GND (Ground) via a jumper wire. (Both jumper wires and resistors come as part of the Arduino kit. You can also buy them in bulk at stores such as Fry's, RadioShack, Amazon, etc.)

Here, we take advantage of the fact that all the components in a row on either side of the ravine on a breadboard are electrically connected. We connect one leg of the resistor to the same row as the positive leg of the LED, and connect the other leg of the resistor to Pin 13. The resistor is used to limit the electric current flowing in to the LED, and to ensure that the LED does not burn out due to direct power from the Arduino. The jumper wire from the Arduino GND (Ground) is connected to the same row as the negative leg of the LED, to complete the circuit. The electric current will flow in to the LED from Pin 13 through the resistor and flow out to the GND (Ground), thus completing the circuit.

Now, click on the green flag on the S4A screen and watch the LED blink...

Blink - Introductory S4A (Scratch for Arduino) Project

Blink is the first project that we shall try on the Arduino board. This is the S4A (Scratch for Arduino) version of the original Blink tutorial on arduino.cc. The aim is to familiarize the students with the board and using the S4A to interact with it. (Detailed setup instructions for S4A can be found on s4a.cat.)

In S4A (Scratch for Arduino), the Arduino board is treated as a Sprite, and appears on the screen as such. You write code for the Arduino, just as you would for any normal Sprite. If you are using multiple boards, you can open up multiple Arduino Sprites.

While working with a new hardware board, 90% of the time, the first step is trying to light up an LED on the board. Not only does it involve the simplest of wirings, but it also provides a visual indication that the connections are fine and that you can communicate with the board. And keeping with the tradition, that's where we shall start too: light an LED connected to the Arduino.

Aim:  

Connect an LED to the Arduino and try to blink it.

 

Materials required:

• Arduino board
• 1 LED
• 1 Resistor, anything between 220 ohm to 1 K ohm
• USB cable connecting the computer to the Arduino

Wiring:

The wiring involved is really simple, and is the same as the Blink example on arduino.cc. As shown below, connect the positive leg (the long leg) of the LED to Digital Pin 13 via the resistor, and the negative leg (the short leg) to the GND (Ground) to complete the circuit. Now connect the Arduino to your computer via the USB cable.

The LED does not require much power to light up, and the Arduino board itself can power it. You do not really need a separate power source such as a battery, for this project. The resistor is used to limit the electric current flowing in to the LED and to ensure that the LED does not burn out due to the direct power from the Arduino. The electricity will flow in to the LED from Digital Pin 13 through the resistor and flow out to the GND (Ground), thus completing the circuit.

The Program on S4A:

The Blink code sets the LED on and off. Here is the code snippet on S4A.

We use an event - "Green Flag Click" - to start the program, just as in the regular version of Scratch. Next, in a "forever loop", we include the instructions to turn the LED on and off, by sending a signal to Digital Pin 13, and then switching it off.

The "digital <NUMBER> on/off" instructions can be found within the "Motion" section of the S4A Instruction Set. The "forever loop", "green flag click" and "wait" instructions can be found in the "Control" section of S4A.

As you can see in the code above, we let the electricity pass to the LED and then switch it off, with a delay of 1 second in between. Why the "wait 1 second" between the instructions? Well, if there is no delay in between, the human eye cannot detect the blinking of the light.

Test:

Now, try clicking the green flag on the screen and watch the LED blink.

You have successfully written your first S4A code, and tested out your Arduino!