Fri, 02/09/2007 - 02:00

How to add an LED indicator light to your cooling fans

Okay, let me begin with this statement: I know nothing about electronics, so if something works once I'm done, I just start counting days to see how long it will last. *sigh*

Sometimes when I turn on my IceCap fans to cool the tank down, I forget and leave them running. I can't use the Aqua Controller II to turn them on and off because the x-10 technology burns up the DC power supplies. I only have to use them occasionally, but there are nights when I wonder why the tank is down to 79F or less. The IceCap fans are so quiet when running in the lowest mode, I don't hear them. Usually the next day I'll figure it out when the lights are on and I hear them spinning at warp speed.

So, I wanted to add a LED to just give me a clue if they are running. That way when I walk by at 3am, I'd have an indicator to remind me to shut them off if necessary. I asked some DFWMAS members for some help, and Russ talked me through it. Thanks to Russ' help, I have a working LED now. Here are all the pictures.

First of all, let me tell you it is SO easy to blow out an LED, I can't believe it. Russ was helping me ascertain which side was the positive side on a 9v battery (via telephone). Sounds simple, right? It turned on for a split second and that was the end of that $1.49 LED. My fault, since I wasn't using the resistor during the test.

Okay, so here are my parts. The resistors and two LEDs were under $5 from Radio Shack. Take note, I was told to use a 600 Ohm resistor, but they didn't have them so I got 680. I figured the bulb would be a tad dimmer as it wouldn't get as much juice. I was right.

The LEDs weren't 3.3V as recommended either. They were 1.7V, but I was told the more important part was 20mA anyway.

I got out my tools. Soldering iron, heat shrink tubing, etc.

I have a feeling if you leave the soldering iron on the LED too long, you'll send too much heat up the diode's wire and cook it. I tried to work fast, and it was a tad sloppy. Here's the first solder, connecting the 680 Ohm resistor to the positive side of the LED.

Then I connected the other end of the resistor to the positive wire going to the power supply.

Soldering on the other side, quickly yet again.

Quick test.

Next, I used a candle's flame to shrink the tubing over the soldered connections. Just keep it moving over the flame, never too long in one spot.

Once done, I had to drill a hole in the fan bracket to hold the LED in position. This is an older bracket I made a long time ago, back when looks didn't count. The LED is clear, so it is almost invisible in this image, facing directly at the viewer.