In this Instructable, I will be guiding you through the process of hacking and converting a clear, 120mm PWM cooling fan used in common household PCs from a single color LED to individually addressable RGB LEDs. The applications of this hack are not only limited to 120mm cooling fans, but anything your creative mind can fabricate. Accent lighting creates a unique aura, customizing the object you are illuminating and creating a profoundly different perception. In this guide, I will be modifying my computer tower to remove large amounts heat generated by the high performance CPU and GPU, in style. With the use of Texas Instruments' TLC5940 - a 16 channel PWM controller - and use of the finely crafted 5940 Arduino library - embedded design becomes extremely simplified for those of us more hardware inclined hobbyists. Additionally, we can stack TLC5940's in parallel, easily allowing us to add more fans to hack and customize all of the fans in your computer!

This is a really fun, simple, safe, and affordable weekend project. In this project, you will learn how to properly solder and tin wire leads, how to create a secure wire harness with strain relief and a sleek, manageable appearance. You will learn how to wire RGB LEDs, how to adapt common cathode or common anode LED depending on the application and hardware being used. You will learn how to configure the TLC5940 and associated hardware, as well as basic operation from a software perspective. You will finally learn how to install a CPU into a computer system, and what techniques are best for dispelling heat from within your PC tower. Finally, you will take this knowledge and gain the ability to apply accent lighting to any object your heart desires, wow to your family, and show off to your friends with your magical ambiance of mystical colorful lights.

Lets begin:

Experience Level: Beginner to Intermediate
Cost Level: Low
Estimated Build Time: 3 Hours

Parts List:

-Standard 5mm RGB LEDS (common cathode(-) is preferred but not required)
-Wire (22g)
-120mm cooling fan
-Soldering Iron
-x12 3906 General Use Transistors
-Zip Ties or Twist Ties
-Super Glue or Tape
-Arduino Uno
-x1 TLC5940
-x1 2kohm Carbon Film 1/8w (or larger) Resistor
-DC Supply (for more LEDs or higher power LED applications)
-TLC5949 Arduino Library
-USB A to B cable

Step 1: 120mm Fan Preparation

The first step is to prepare the fan to installation of the RGB LEDs we will be replacing with the boring single color provided. For the fan, I used a generic eBay fan - found for 5$ (with free shipping).

They are low in cost, easy to work with, and operate fairly quietly. The LED's are very easy to access, remove, and replace. Many times, when purchasing the fans, it is not mentioned what size the LED is that comes OEM from the manufacturer. My fans particularly came with green 5mm LEDs - voltage drop and current will be somewhere between 2 or 3vdc at 30mA (max).

Luckily, I had 5mm RGB common cathode(-) LEDs laying around from previous projects. They are a terrible quality LED, but they are great for prototyping because they are so affordable. You can find them in bulk on eBay - I believe mine came 10$ for around 100 of them. Sometimes, they can even be found in the "top hat" style -- or wide viewing angle for maximum light dispersion. This is great for because the light is "thrown" around more than the traditional directional LEDs. The top hat style will not fit securely into the LED sockets of the fan, so glue may be needed if you choose wide viewing angle LEDs.

Identify and Remove LEDs

Begin by identifying the four LEDs of your fan, located in each corner. There will be a very thing + (red) and - (black) wire going to each diode (LED) from the PCB.

-Take a small pick, probe, or screwdriver to gently push the LED out of the socket - from the inside of the fan pushing out. Placing the tip of the pointed object, and placing it on the center of the LED and pushing outward. The LED should slight out very easily.

-Repeat this process and remove all 4 LEDs.

-Clip the LEDs off leaving enough lead length to potentially use the leads coming from the fan if we decide. Also leave enough lead length coming off the LEDs to use them if we require them for any future projects: we don't want to be wasteful!

With the single colored LEDs removed, you should have four empty 5mm sockets, one on each corner. These sockets are where we will be placing the RGB LEDs. But, do not place them yet. We have to prepare the LEDs for the install. We don't want to do any soldering in close proximity of the plastic fan. Lets move to the next step and prepare the LEDs and the wire harness.
<p>Thank you for the excelent explenation of what you did with the TLC chip. It inspired me for my project. (Clich&eacute;) Led Stairs</p>

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