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Introduction to Electricity

Much of the following text and pictures were copied and slightly modified from http://www.ladyada.net/learn/arduino/lesson3.html under http://creativecommons.org/licenses/by-sa/2.5/ as such, this page is subject to the same license.

Say hello to the solderless breadboard!

Solderless breadboards are an important tool in your quest for electronics mastery. They allow you to make quick circuits, test out ideas before making a more permanent Printed Circuit Board. They're also inexpensive and reusable. You can pick on up at any hobby shop or electronics supply store. They often look like this

Basically, a chunk of plastic with a bunch of holes. However, something special is going on inside the breadboard! Although you can't see it, inside the breadboard are many strips of metal that connect the rows and columns together. The metal strips are springy so that when you poke a wire into the hole, the clips grab onto it.
In the images above you can see how there are two kinds of metal strips. There are short ones that connect 5 row holes at a time, and then there are very long ones that connect 25 (or more!) column holes at a time. The long columns are called rails and the short strips are called rows. Breadboards are almost always made so that they have two sets of 5-hole rows and on either side there are a pair of rails. For example the breadboard on the left has 30 row pairs and 2 sets of double rails on either side. The one on the right is quite small, it has only 17 row pairs and no rails.

Warning!
Distressing as it may sound, solderless breadboards can be very flakey, especially as they age. If you're having problems with your circuit, it could be that the little metal clips on the inside aren't working well. Try poking it with your finger, or moving it to a different section.

Say hello to the resistor!

Make Presents: The Resistor

The resistor is the most basic and also most common electronic part. An electronic gadget, such as an mp3 player has easily a
thousand resistors inside of it!

Resistors have one job to do, and that is to resist the flow of electricity (otherwise known as current). That's why they're called resistors. By resisting current they control where and how fast it flows. One common way of thinking about this is if we were talking about water current, then pipes are like resistors. Thin pipes let less water through (high resistance), thick pipes let a lot of water through (low resistance). With a fire hydrant, you want low resistance. With a water fountain, you'd want high resistance. If you mixed up the two pipe sizes, you wouldnt be able to put out a fire and you'd hurt yourself while trying to get a drink.

Resistance is measured in ohms, often written as the symbol Ω. The bigger the resistance value (in ohms) the more it fights. Most resistors you'll see range between 1 ohm and 1 megaohm (1.0 MΩ). Since the resistive element is inside a ceramic casing, its not possible to tell the resistance of a resistor just by looking at it. You'll have to read it by looking at the colored stripes on the body of the resistor. This is known as the resistor color code, and its a real pain when you first start electronics. Eventually you'll get really good at telling the value of a resistor just by glance but to start off you'll want to use a reference chart. (Or you can use a multimeter to measure the resistance accurately


Remember: Just because the stripes are in a certain order doesn't mean the resistor has a direction! Resistors are the same forward and backwards, it doesnt matter which way they are used.

Say hello to the LED!

We've had some time with the LED already, but lets get to know her a little better. The word LED stands for Light Emitting Diode. The light-emitting part, well, that makes sense. We've used the LED to make a blinking light in on our Arduino board. The LED component turns current into light, much like any sort of light bulb. But what is this mysterious diode?

A diode is basically a one-way street for current. Imagine such a one-way street with a traffic policeman in front. If you want to turn onto the street the wrong way, he will not let you. Likewise the diode simply does not let current go through it the wrong way. Current in a diode can only flow from the positive side to the negative side.

As we mentioned before, its easy to figure out which side of an LED is positive and which one is negative. The positive leg is slightly longer and if you look inside, the chunk of metal is larger on the negative side.

Make Presentes: The LED

Light up my breadboard

We're going to now use the breadboard to light up an LED. You will need a breadboard, an LED and a 330K ohm resistor orange orange brown gold). You'll need 2 jumper wires as well.

Important Note!
While LEDs will not work when placed backwards, you don't have to worry about whether it will be damaged: as long as there is a series resistor of at least 100 ohms next to it, the LED will survive the experience!

However, using an LED without a series resistor is a sure-fire way to kill it! (You'll see a bright flash and it may turn dark)  Always use a resistor! A 1.0K ohm is a good place to start. We'll cover how to figure out the best resistor value later on.

You'll need to use wires to reach the Arduino. Run one wire (red) to the 5V socket on the Arduino. Run the other wire (black) to one of the GND sockets on the Arduino. The colors aren't essential but they will help you remember what the wires are connected to!

Plug in the Arduino, you should see the LED light up. If not, check the following:
  • Is the Arduino plugged in? (look for the little green light on the Arduino as in lesson 0)
  • Is the LED in backwards? Try flipping it around, just in case. This wont damage the LED.
  • Are the parts firmly placed in the breadboard? Loose parts are a common breadboard problem, try jiggling them with a finger and see if it starts working.
  • Is the LED on and its just very dim? Try turning down the lights or looking at it head on: some LEDs are very directional.
  • Is the red wire going into the hole labeled 5V? Is the black wire going into one of the holes labeled GND?
  • Try another LED in case this one is damaged
  • Make sure the parts are as shown in the image above, if you have a wire in one row and the resistor in the other, they aren't connected and it wont work!
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