Replacing Case Fan LEDs

After deciding on a case for my computer (Antec Nine Hundred Two), I decided that I no longer cared for the color blue in LEDs. Not that colored LEDs on a computer case do a whole lot, but I figured that if my case was going to glow, it wasn’t going to glow some overused color like blue. These days it seems like every case either glows blue, red, or green. Hooray. I require something a little more unique.

Image courtesy of http://www.antec.com/

After some pondering, I decided that orange would be nice. I like orange. And it matches my Logitech G15 keyboard (because nothing screams nerd like matching computer gear). However, after some searching on the Googles and the Neweggs, I discovered that no one sells orange LED fans. That makes me a sad panda. Obviously, the only solution was to bust out the trusty soldering iron and replace all the LEDs myself. Take that Antec.

What You Need

Here is a list of the equipment you will need. The small components (LEDs, resistors, heat shrink) can be obtained from http://www.digikey.com/. These have a part number listed in brackets. Note: If you are just working with the regular TriCool fans, you need 3mm LEDs. If you have an Antec case with one of the massive 200mm fans, then you will need 5mm LEDs as well. Also, I always recommend ordering more than you really need, as LEDs, resistors, and heat shrink tubing are really cheap.

• Antec TriCool Fans (the Big Boy 200mm fan comes from the 900 Two case)
• LEDs
  • 15x 3mm Round Clear Orange LED (601nm wavelength) [754-1250-ND]
  • 4x 5mm Round Clear Orange LED (601nm wavelength) [754-1271-ND]
• Resistors
  • 19x 68Ω 1/8W resistor [CF18JT68R0CT-ND]
• 1/16″ Heat Shrink Tubing [Q2F3X116B-ND]
• Hot glue gun and hot glue
• Soldering iron and solder
• Flux (match to the flux in the solder core)
• Rubbing alcohol
• Small, cheap paintbrush
• Heat gun
• Electrical tape

Design

Right now, we have blue LEDs attached to the central controller in each fan. From my experiments, there is a constant current source that supplies around 20mA to each LED, regardless of the voltage drop across the LED (what this means: it doesn’t matter what color LED we put it. A simple swap would work). However, let’s assume that you are working with a constant voltage source, and you want to replace the blue LED with an orange LED. Normally, we see a 3.4V drop across blue LEDs, and orange LEDs generally see a 2.0V drop. Therefore, we want to lower the voltage drop while maintaining the 20mA current through the LED. If you want to verify this, put a voltage meter across the blue LED when it’s on and read the voltage – it should be around 3.4V.

We want to clip the blue LED out and replace it with an orange LED and a resistor. This will limit the current and drop the voltage to an acceptable level (2.0V, in this case). We will put a resistor in series and calculate the resistor value as follows:

I = 20mA
3.4V = I*R + V_LED
3.4V = (20mA)*R + (2.0V)
R = 70Ω
R =~ 68Ω (closest resistor)

Soldering

I know that many people complain about soldering….but it’s really not that difficult. I promise. There are only two rules when it comes to soldering:

1) Don’t burn yourself.

2) You’re going to burn yourself.

With that in mind, fire up that iron. To help you make the LED swap, I’ve created a step-by-step guide. And because LEDs continue to confuse me, here’s a picture to help you (image courtesy of: http://en.wikipedia.org/wiki/LED_circuit):

1) Mark the + wire on every wire pair running to the blue LEDs (e.g. wrap tape around the wire). This is the wire that connects to the round side of the LED (see pic above).

2) Cut the blue LEDs off as close to the solder joint as possible. Cut the wire and not the LED leads.

3) Strip the wires about 1cm from the cut end.

4) Tin the stripped wire ends

• Apply flux to exposed wire
• Load soldering iron tip with a ball of solder
• Drag solder ball across wire so that the wire absorbs the solder

5) Important: Place ~1cm strip of heat shrink tubing on every wire. If you forget to do this, you will have to carefully wrap each solder joint in electrical tape (not fun).

6) Cut orange LED and resistor leads – leave about 1cm.

7) Bend small hooks into all wire ends, orange LED leads, and resistor leads.

8) Connect the components together:

9) We want to solder the hooks together in the following fashion (image credit: workmanship.nasa.gov):

• Hold soldering iron in one hand and solder in the other. It’s often useful to have a set of “helping hands” to hold the components together.
• Place soldering iron tip on the joint such that the tip touches and heats both the lead and the wire end.
• Feed solder into the joint on the other side (we want the solder to touch the joint, not the iron tip)

10) Important: use the paintbrush and alcohol to clean the flux off all of the joints. Flux will slowly eat away at solder. Even if you’re not using flux, most solder has flux embedded in the core, so you will need to clean anyway (note: if you’re using “no-clean” flux, you can skip this step).

If you’re interested in learning more about good soldering technique: http://www.aaroncake.net/electronics/solder.htm

11) Test the LEDs to make sure you have soldered them properly. Hook the fans up to a 12V power supply (such as the one in your computer), and make sure all the LEDs turn on.

12) Move the heat shrink tubing up so that it covers the joint. Then use a heat gun (a hair dryer will work in a pinch) on the tubing so that it shrinks and wraps around the joint.

Attaching the LEDs to the Fans

1) Run the wire into the grooves on the sides of the fan. This may require a bit of finesse to make sure the wires lay flat.

2) Use a dab of hot glue to secure the wires in place.

3) Now, do your best to carefully bend the LED/resistor set into a shape that conforms around the fan and in such a way that the LED fits snugly into the hole.

4) Use another dab of hot glue to secure the LED in place.

5) Test the fan and LEDs again to make sure everything works.

Finish

Just put everything back together, and bask in the warm orange glow of your new case. As a side note, computers with orange LEDs don’t run as fast as computers with blue LEDs. They just look cooler.