The circuit is the basic building block for any electronics project. A circuit includes all of the electronic components required for a task as well as wires or another material which will let the electricity flow between the connected components. Electronic circuits describe a complete and closed loop.
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There are two main parts that make up a circuit: conductive lines and components.What are components? LEDs, transistors, resistors, diodes, and all of the parts that control the flow of electricity or have another function in our circuit. Conductive lines are often metal threads or wires, as metal is a good conductor of electricity.
The Breadboard
Components are often attached to each other on a solderless breadboard. What’s that? A solderless breadboard has rows and columns of metal strips encased in plastic with a grid of holes called tie-points on the top. It allows us to quickly build circuits without having to permanently connect the components (by soldering, for example). Here’s an “x-ray view” of a breadboard.
There is a pattern to how the metal strips are arranged on a breadboard. There are long strips along the left and right of many breadboards that are used to attach power and ground in a circuit. These long columns are called busses. The power bus is marked with a red plus sign, the ground bus with a green, blue or black minus sign.
The rows also have connected tie-points. In the drawing below, the breadboard has many rows of 5 tie-points, on either side of a trench. Each tie-point in a horizontal row as shown below is connected. The rows of tie-points on either side of the trench are NOT connected, each side has a discrete row of 5 points that are connected.
This drawing shows how components are attached on a breadboard; the leads of the components are in the same row of tie-points.
Connecting the breadboard to an Arduino
How do you connect a breadboard to an Arduino to build a circuit? Let’s build a circuit that connects a breadboard with an LED and a resistor to an Arduino.
You will need these parts:
- Arduino Uno
- solderless breadboard
- USB A-B cable
- LED
- 220 Ohm resistor
- jumpers
A note about LEDs
An LED (light emitting diode) has an orientation, or a positive and negative lead. An LED must be placed into a circuit properly, with the positive and negative lead oriented properly. How do you know what is the positive and negative side? The positive side has a longer lead. It is called the anode. The negative lead is shorter and called the anode. Also, the negative side of an LED often has a flatter side at the bulb.
Start building!
Before you start building, make sure your Arduino is not attached to your computer. Never make changes to a circuit when power is attached.
Attach jumpers from the 5V power pin on the Arduino. Your teacher should have some jumpers, they are pieces of wire used to make connections between components. You can make your own jumpers as well, by using 22 gauge hook-up wire and stripping the coating off the ends.
Next attach a jumper from pin 13 on the Arduino to a row of tie-points on the breadboard.
Place one end of a 220 Ohm resistor in the same row of tie-points as the jumper from pin 13, and the other end in a different row of tie-points.
Now let’s place the LED in the breadboard. Put the anode (long leg) of the LED in the same row of tie-points as the resistor. Put the cathode (short leg) of the LED in another row of tie-points.
Finally, place one end of a jumper in the same row of tie-points as the cathode of the LED and the other end in the ground bus. You have just closed the loop and made a circuit.
Now you have built the circuit! Hook up the Arduino to your computer. If you have already downloaded the Blink sketch, your code is loaded on the Arduino, and the LED should start blinking right away. If you haven’t downloaded the Blink sketch, open up the Arduino software. The Blink sketch is at the File Menu > Examples > 01. Basics > Blink.
Further reading/resources
