20 LED Arduino String Made From Lan Cable

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riaancornelius thanks a lot for making the tutorial about charlieplexing i have learned a lot because of you! His instructable can be found over here https://www.instructables.com/id/Controlling-20-Leds-from-5-Arduino-pins-using-Cha/

In this tutorial we are going to make LED Christmas Lighting based on the Arduino prototyping board. The Christmas lighting will be based on 20 LEDs.  This project is going to be both relatively cheap and incredibly awesome. We will be using a technology called Charlieplexing which is frequently used in Arduino based projects. The reason for this is that we do not want to use a pin on the Arduino board for every single LED.

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Step 1: More on Charlieplexing

Charlieplexing is the main part of this project,so let me elaborate on that. Due to a shortage of pins on the Arduino board people came up with several solutions. E.g. multiplexing and charlieplexing, the latter will be used in this case due to limited wires in a LAN cable.
For a LED to work you need current flowing from HIGH to LOW. For example to make LED1 burn PIN1 is HIGH and PIN2 is LOW. However the state of PIN3 could influence this schematic. Therefore in charlieplexing every unused pin goes into what’s called a tri-state, setting this pin as an INPUT. Those have very high impedance therefore very little current will leak out there.
Example: To turn on LED6. PIN1 is LOW, PIN2 is INPUT and PIN3 is HIGH

This technology is not very impressive when only using six LEDs, however when we expand the amount of pins we discover that this system can connect {pins(pins-1) = LEDs} in the case of 5 pins this is 5x4=20 LEDs, exactly the amount we want.

Step 2: Gather Materials

You will need
- A LAN cable
- 20 LEDs in a color of your choice (though keep in mind that they need to be quite bright)
- 6 75& resistors
- Arduino
- USB cable
- Soldering iron
- Knife
- Computer

Step 3:

First of all make sure you know this schematic from top to bottom. Write additional info on it like for example the color of the wire, so you will not connect LEDs to the wrong wires. Finding out afterwards is quite a lot of work.
Indicate on the LAN cable where you want the LEDs to be.Having them at a set distance apart looks quite a lot better than having 15 LEDs on one side and 5 on the other. An alcohol based marker would be best for this, however any indication would do. Start cutting away some of the outer isolation of the LAN cable so you can work with the smaller wires inside.
Then the real constructing will begin. Connect the LEDs to the right cables in the LAN cable, and make sure you use the cathode or - and anode or + (long leg) side of the LEDs appropriately. LED 1 would have the long leg connected to the orange wire and the short leg to the blue wire and so on for the other nineteen LEDs.
When all this is done connect the resistors to the wires and plug the resistors in the Arduino pins 8, 9, 10, 11 and 12.

Step 4: Tips Tricks Mistakes?

Most likely a few mistakes will occur. These tips will help you fix that.
- If you run the test program, and more than one LED turns on, the LED that was supposed to turn on is not connected properly.
- If LEDs turn on in the wrong order.  The LEDs are most likely connected the wrong way around. An easy way to fix this can be found on the website where the sketches are available.

Tips
- Try to find a LAN Cable without shielding
- Take bright LEDs preferably with a wide angle
- Buy a little extra in case you lose some parts
- Get a proper soldering iron.

If any question just contact me! I will try to help you as much as possible!

The current effects are just proof of concepts. I will however try to make more effects as soon as possible. If anyone has any improvements on this projects please do tell

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