Hi. I am Dog digger.
I will be showing you the ins and outs and all the details about LEDs. This has taken me a long time to make.
LEDs. They are awesome! They are essential to life today. They are used everywhere and you can get them almost everywhere. You can do so many things with them and I will show you the types and what you can do with them, some projects and more!
Don't forget to comment and vote in the LED contest!
please don't be too critical, I'm only 13 years old
Step 1: History
The technology of LEDs started with electroluminescents. This was experamented in 1907 by a experamenter by the name of H.J Round in Marconi Labs in England. He experamented with a single peice of the element, silicon (which i will explain later) and a cat's whisker detector which consisted of a thin peice of wire that connected to the anode and the base of the semiconductor connected to a cathode. A voltage was applied and light was produced in the form of electro luminescence. however the LED was not fully introduced. The idea was abandoned. In 1961, the first real LED was born. Two Texas instrument experimenters made the first infra-red light produced by a single piece of Gallium arsenide. This is a material that consisted of gallium and arsenic. They received a patent for the LED and they were introduced to the world. The first visible spectrum LED was made in 1962 by Nick Holonyak Jr in GE electronics. Back then LEDs were horribly expensive costing $200 a unit. That was... until 1968. A company by the name of the Monsanto Company first mass-produced these red LED indicators using the Gallium Arsenic that was used before. In that same year, HP also mass produced LEDs with the GaAs (gallium arsenic) that Monsanto supplied them with. Hp used them in their calculators instead of LCD screens. In 1970 Fairchild Optoelectronics ( with the help of Fairchild semiconductor) manufactured the LED for only 5 cents! Using the planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor and innovative packaging, optoelectronics pioneer Thomas Brandt led the team at Fairchild semiconductor and they were successfully producing LEDs for low prices. Later on down the track, companies use different materials other than GaAs and produced different colours. The first High Output blue LED was created by Shuji Nakamura of Nichia Corporation in 1993. He used a combination of different materials to create this LED. Later, the high brightness White LED was made by this same man and he received many awards. Today, you can get almost and LED to suit your needs. LEDs are truly awesome!!
Step 2: Take a Look inside......
Inside the LED you will find a few interesting things. If you have a waterclear casing, you can easily see whats inside. Like you see in the picture, the first thing you will notice is the lead posts. The LED is in a epoxy casing and the lead posts are held secure by the epoxy casing. Then there is the semiconductor assembly. Inside there you will find that there is a reflector cup. This is to direct the light from the semiconductor chip up and out of the casing. The way you can tell the posetive of the LED is if you look carefully inside, you can see the small internal post is the posetive 'Anode' and the bigger internal post is the negative or the 'Cathode'. The semiconductor chip is a peice of silicon crystal with a chemical coating that provides the different colors. In some special LEDs, the have multiple cystal sets and a common cathode or a common anode to create a 'dual' or 'tri' LEDs. Some LEDs have built in flashing circuits to alternate between colors. I like those RGB LEDs (thats what they are called) but they are usualy more expensive than stndard LEDs.
Step 3: The types
In this step I will explain the various types and packages of LEDs. There are so many types it's not funny! I will explain most of the packages available. The most common package is the 5mm round LED. You can get almost all LED colors in this package. There are LEDs that are pretty much the same but are in either a 3mm or 10mm package. These are the most common LEDs you can get. Every one I have talked about above are available almost everywhere. you can get "box" LEDs and they are in a rectangle package. There are a few variations to the round LED e.g it might have special features like a flat top so the LED is basically like a cylinder. There are two types of the LED surface. Diffused and Water clear. A diffused epoxy coating is dull with the colour of the LED and it will not 'throw' the light very well. Water clear LEDs have a transparent lens and are excellent at 'throwing' the light. You will commonly find water clear LEDs in lighting effects and flash lights but I thing that their uses on application are unlimited. Now I'll move on to speciality LEDs.
Step 4: Speciality LEDs- High Power
The first type of specialty LED is the High Power LEDs (HPLED) and they are very special. They drain more power than standard LEDs but they offer high light output. The origional problem is this. People who wanted LEDs to produce lots of light got a lot of standard LEDs and put them in a big LED array. These were very common in flashlights. But when people crammed so many LEDs into one light, problems arose. The first was the problem of size. The head of the flashlight was very big and the light output was not increased that much per LED added. A well known fact is "One 100watt light bulb emits more light than three 33watt light bulbs" . So people developed the High Power LED. It requires special drivers but once you have a driver, they are almost as robust as a standard LED. High Power LEDs require a heatsink because they get warm and if there wasn't a heatsink, the LED would burn out very quickly. These LEDs are popular in flashlights because they are very efficient and they have very high light output for their size. They can be found in many different power ratings and sizes. Once I saw a 60W LED!
Step 5: Bi-LEDs and Tri-LEDs
These special LEDs combine multiple LEDs in one package. These LEDs have either a common anode or a common cathode. Common cathodes are more common. They can be diffused or waterclear. Most Bi-LEDs have red and green LEDs but they are available in different colour combinations. Tri-LEDs are the same thing but with three LEDs built into it. There is not much to say about them. They are pretty simple unless you plan to light them all at once. Then things start to get more complicated. You need to find the individual voltage drop of each LED and you can often find the details on the datasheet. Then you need to calculate the resistor value and I'll explain that later. To find the datasheet ask at the counter at you electronics store at which you bought it. If you recycle one from a circuit board, experiment. Google is also you'r friend.
Step 6: RGB Flashing and flashing LEDs
These are special LEDs. The flashing LEDs are a standard LED but with an integrated flashing circuit. Its sort-of like a strobe. The average flash rate is 2-4htz (times a second). These are useful for warning indicators or just for fun. They are normally available in the same sizes as standard LEDs. My personal favourite, the RGB sequencing LED. These LEDs are special. They are 3 LEDs (red,blue,green) in one package with a built-in colour sequencing circuit. This creates an awesome effect. The circuit sequences between each colour at a rate of about 1htz per colour. Both of the LEDs I have talked about look like standard LEDs.
Step 7: SMD LEDs
SMD LEDs, like any other SMD device, are tiny. SMD (surface mount device) is a category of components that are more compact and they are soldered directly onto the surface of the PCB (printed circuit board). Companies use SMD in their products because they are so small and compact. If you open up a modern phone, there will be barely any through-hole components. SMD LEDs, like standard LEDs, are available in different sizes. 1mm to 4mm but they aren't rated like that. Like most SMD components, they are identified in size numbers. The numbers are determined by Width (inches) multiplied by Length (inches) Ok enough with SMD. These LEDs don't have the epoxy coating so that the light is focused so, the viewing angle is wider. Superflux LEDs are a type of SMD LED and they are commonly found in animated billboard advertising and public transport.
Step 8: Misc LEDs
I have talked about the major LEDs but there are a few others. There are LEDs in Bezels that can run on 12v or a LED lamp instead of a incandescent or a CFL. There are so many variations that would be almost impossible to list
Step 9: LED resistors
This step is simple. Ohm's law was first daunting to me but when you read this step, it will be a walk in the park
If you want to use an LED with anything other than it's rated voltage, you will need a resistor. I'm sure you have heard of these. Resistors limit the current and they are rated in ohms (see ohm's law). To find this, use ohms law. If you think this is too hard, use a online calculator (link here)
VS = Supply Voltage
VL = LED Voltage
I = LED Current
Lets break it down
If I wanted to use a LED with a voltage drop of 2v and a current of 20ma, and I wanted to use a 9v power source, the equation would look like this
So that the resistor we would need would be 350ohms but if that is unavailable, always go up in the resistor value to the nearest value.
Step 10: LEDs in a circuit
Some might think that the symbol for an LED would be the same as an lamp, but that is incorrect. An LED is actually a diode. They only let current flow in one direction. LED stand for Light Emitting Diode. The first picture is a simple circuit diagram for wiring and LED. It's really that simple! Do not connect LEDs in parallel with only one resistor unless they are identical. For a high power LED, you need a special driver board, just like lasers. If you connect them in parallel with their own resistor, that will be fine. If you connect LEDs in series, add all the LED voltages and that will result in the input voltage you will require.
Step 11: Projects
Now I will be showing you some projects you can do with LEDs.
Step 12: LED Throwies! step one
LED throwies are fun and awesome. They are simple and look awesome.
They are simple to make and that is why they are the first project
1. LED. Any with two leads will do
2. 3v Button cell battery
3. electrical tape
4. (optional) neodymium magnet.
Step 13: LED Throwies! step two
Test the LED. Attach the longer lead of the LED (the anode) (positive) to the positive side of the battery. The LED should light up. If it doesn't, swap pins.
Now Wrap the LED and battery with electrical tape.
If you have a magnet, wrap it with tape with the LED and battery
Step 14: LED Throwies! part three
All done! With the magnet, you can toss it at a metal surface and it will stick to it. To use them, toss it around at night. Try and flick it to get a flashing affect. I have added a video but it doesn't the full effect of the LED throwie
Step 15: Project number 2: Sync LED light to music
This is a simple project that allows you to convert a audio signal into light with a transistor.
All you need for this project are four parts:
1. LED. Almost any standard LED will do.
2. Audio jack for input
3. 3v power source. 2x AA batteries would work best
4. Any NPN transistor. I recommend a 2N3904
Step 16: Sound to Light: step 2: The circuit
It doesn't really matter how you make it as long as you follow the schematic but for those who don't understand them i will quickly give you a crash course. The LED is symbolised as the diode with the arrows. The battery is symbolised with the longer and shorter lines and the + sign and the "B". Any power source would be a longer line for positive and a shorter line for negative. The little arrows pointing downwards are the ground symbols.The text "audio in" is self explanatory. I couldn't find a symbol for it. The big thing in the middle is the transistor. The collector, base and emitter is highlighted with image notes. The audio in is connected to the "base" of the transistor. That is normally the middle pin on a transistor. The "emitter" is connected to audio and battery ground. The "collector" is connected the the negative of the LED. Now, Lets start making!
Step 17: Sound to light: step 3: assembly
1. Lets start with the audio jack. Strip the ends and join the left and right (usually the white and red) together. Now tin these connections with solder.
2. Solder the Left and right cable to the base of the transistor. This is the middle lead.
3. Solder the ground to the emitter. This is the 3rd pin.
4. Now solder the Negative (often shorter lead) of the LED to the collector of the transistor. This is the remaining lead.
5. Now solder the positive of the LED to the positive of the power source.
6. Solder the negative of the battery to the circuit's ground.
Step 18: Done!
Plug it in and test it out!
You are done with the sound to light circuit!
This circuit has a lot of potential and it is so compact that it can be put almost anywhere. It is so useful and universal. You can house it almost anywhere! I have put this in a headphone amp (Se that here) and a battery holder and I have used this circuit many times.
Step 19: Ultimate LED guide
I hope this LED guide will help a lot of people and I hope your knowledge has grown!
LEDs are truly awesome and help the world see their awesomeness!
Step 20: Thank you!
Thank you for viewing this LED guide!
Please vote for me in the contest and comment and rate