The Board of Education Shield has a device called a voltage regulator that supplies 5 volts to the sockets labeled 5V. So, 5 V of electrical pressure causes electrons to flow through the circuit electric current , and that current causes the LED to emit light. This makes the voltage the same 0 V at both ends of the circuit. Volts is abbreviated V.
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Ground is abbreviated GND. The term ground originated with electrical systems where this connection is actually a metal rod that has been driven into the ground. Current refers to the rate at which electrons pass through a circuit. If you have a regular breadboard you'll need 2 jumper wires as well. While LEDs will not work when placed backwards, you don't have to worry about whether it will be damaged: 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! We'll cover how to figure out the best resistor value later on. Place the resistor and LED as shown. Make sure the longer leg of the LED is to the right, connected to the resistor. The resistor doesn't have a direction, so it doesnt matter which way it goes in. Click for a high resolution photo if necessary! If you're using a standard breadboard, 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! Hooray, you just built your first circuit! Its quite simple but still worth explaining. Basically you've connected the LED and resistor in series one after the other to a 5V 'battery'.
The positive pin of the LED is connected to the positive terminal of the battery, then the negative pin is connected to a resistor which goes to the negative terminal of the battery. The battery is supplying the current that flows through the LED, making it light up. The positive and negative battey terminals are often called the power supply , as they supply power to our circuit. The positive terminal is called power as thats where current flows from and the negative terminal is called ground , as it is where current flows to.
Lets say you want to "save" this design and send it to a friend to check out and build for herself But a better way is to draw a wiring diagram. Then it wouldn't matter if your camera wasn't very good. A wiring diagram is also known as a schematic. Schematics are the standard method for people to trade information about circuits. Being able to read and write schematics is a key skill! Here is a schematic for a really big project, a Roland TB synthesizer clone.
Powering a series circuit:
Each electronic component has a schematic symbol, which is a simplified drawing of the part. For resistors the symbol looks like this:. LED symbol, positive pin on the left, negative pin on the right. You can see that the resistor symbol is symmetric, just like resistors themselves. The LED symbol, however, has an arrow thing going on.
This is the direction in which current flows. The little arrows that are coming out of the symbol indicate that this is a diode that emits light. Power and Ground symbols. The only thing we need to do now is indicate how the LED and resistor are hooked up and show the 5V and ground connections. Next to symbols, we often write important information like what the resistor value is, what color and size the LED should be, and the voltage associated with the power supply.
A well documented schematic! Before you change your breadboard, make a guess of what will happen: Will the LED stay lit? Will the LED go out? Now make the change to your breadboard:. You will notice that, in fact, the LED has gone out. That is because it is no longer connected to a power source and current is not flowing. If you were very fast at it, you could make the LED blink! Start up the Arduino software again and open up the MyBlink sketch from lesson 2.
If you left it with delay times of 10ms, you may want to modify it so its back to ms on and ms off.
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Upload the sketch to your Arduino. Now change your breadboard wiring so that it matches this schematic.
That is, instead of connecting the resistor to 5V or ground, connect it to the Arduino pin socket labeled You should see the LED turn on and off. Lets look at that code again. We didn't quite explain what digitalWrite does, but now it should be clear: You may want to think about how cool it is for a few moments. The LED isn't be blinking anymore! Go back to the beginning of the sketch and find this line again. This is the line of code that indicates which pin is connected to the LED. Change it so that it is now connected to pin Re-compile and verify the sketch, then send it over the the Arduino.
The LED should now be blinking again.
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Thats because its connected to pin 13 only! OK sure you've had plenty of practice messing around with LEDs. It's time to go full color! Find a red, green and blue LED. You can't tell which one is which until they are lit so just build the circuit and then rearrange them if needed. Red, green and blue LED schematic. In this schematic we will have three LEDs connected to three different pins: Quick quiz What does this sketch do?
Compile and upload the sketch to test your hypothesis. Highlight the text below to see the answer It blinks the two LEDs connected to pins 11 and 12 at the same time. Add the line of code that will create a variable called bluePin. What pin should it be assigned? Examine the schematic above to find out. Add the line of code that will tell the Arduino that bluePin is a digital output. Compile and verify your code. If not use your debugging skills to figure out what is wrong and fix it!
Overview of this week's lab.
Now that you have red, green and blue light, you can start having fun with color mixing. Color mixing is the neat ability that our eyes have to combine different light colors and create a new color. They often look like this Basically, a chunk of plastic with a bunch of holes. Heres how to do it with just diagonal cutters Cut the wire first, using wire cutters Nick the insulation, then pull it off.
To connect rows together, just stick the wire ends without insulation into the square holes!
Now is a good time to practice making jumpers, go forth and make a few 3" long jumpers! There are also website calculators that you may find very handy Remember: Highlight the text below to see the answer Red - Red - Brown - Gold What is the value of this resistor? Highlight the text below to see the answer Ha! Trick question, it is not possible to put a resistor in 'backwards'.
They work either way! Here is a schematic for a really big project, a Roland TB synthesizer clone Each electronic component has a schematic symbol, which is a simplified drawing of the part. For resistors the symbol looks like this: