Cheap and Cheerful Switched Case Fans




Introduction: Cheap and Cheerful Switched Case Fans

About: I like rabbits

This is how I added 2 extra fans to my computer with nice big illuminated switches using stuff I had lying about. I know you can get 5 1/2 inch bay mounted fan controllers pretty cheap nowadays but I think this is cooler.

Step 1: Why I Did This

You may be wondering why I bothered with this.

Today I was playing musical drives because I have a DVD-R and a HDD that really dont like each other, and I have a pile of CD's to duplicated (all public domain.) So I decided to swap the HDD for an extra optical drive.

When I pulled my computer apart I discovered that pretty much everything was hotter than I would like, especially the HDD's (I have 4) so I decided to shove a spare fan I had into the back of the case, I was too lazy too mount it next to the Hard Drives because it would mean pulling half the components out. When I turned it on the extra fan worked great, but it sounded like a vacuum cleaner and it wasn't really blowing air over the drives like I wanted so I decided to something more elaborate was in order.

Step 2: You Will Need

You will need the following

Some 12v Fans (I got mine from PSU's as they tend to be more powerful)
A 5 1/2 inch Blanking Plate
Some SPST 12v illuminated switches (or just SPST switches) 1 per fan
Hookup wire (must be good for 1/2 amp or so)
Mounting screws / bolts
Molex "Y" connector or female molex connector
Electrical Tape


Wire Strippers
Soldering Iron
Hot Glue Gun (optional)
Drill / Dremel Tool

The switches I used are from maplins which I intended to use for another project that never got started. See the closeup image for the pinout. You can use normal SPST panel mount switches and the wiring will be a bit simpler.

Step 3: Mark and Drill the Blanking Plate

Take your blanking plate and mark where you want your switches. If like my you are going to cut the holes using a dremel style tool I suggest you draw on a circle of the required size before you start drilling. I ran a pencil around the inside of a plastic spacer that came with the switches and then "killed" the line. I had them fairly close so as to leave room for future ghetto mods.

The holes don't have to be too pretty as most panel mounting switches have a nice wide collar when they are fitted and cover up most mistakes.

Step 4: Make the Common Connections

Mount your switches on your blank plate make sure they are all the same way up. Then using some hookup wire connect all the +12v (power) pins together and all the Gnd pins together and leave a little tail on each so we can connect them up in the future. I just twisted my connections at this point.

If you have a 12v supply available at this point you can hook it up an test the switches, they should illuminate in the On position and go dim in the Off position.

If you are using normal SPST switches you will just need to make a common +12v on the back of your switches and then connect all your Gnd wires together later.

Step 5: Extend the Fan Leads

Use hookup wire to make the fan leads a few foot long. If like me you only have orange wire left then make sure you know which lead is which. Your hookup wire must be capable of carrying the full load current of your fans (upto about 1/2 amp.)

My connections are still only twisted at this point.

Step 6: Mod Your Molex Connector

Take your "Y" connector and cut the wires from one of the male ends, leave them nice and long. You want the yellow (12v) and one of the black (Gnd) wires.

After I took this picture I cut the red and other black wire right back and taped the ends so you basicly had a short little F->M lead with 8 of yellow and back wire coming out.

Step 7: Connect Everything Up

Now its time to connect everything together.

Connect the +12v (normally red) from the extended fan lead to the center pin of your switch. If your using normal SPST switches then just connect them to the other side. Repeat for each fan / switch combo.

Now connect All your GND wires from your fans to the GND tail from your switches. If you used normal switches then just connect them all together.

Then connect the yellow wire from your molex connector to the +12v tail on your switches

Finally Connect the black wire from your molex to the GND tail from your switches, or in the case of conventional switches to the collection of fan GND wires.

If you have a 12v supply you can now test your rig, each switch should illuminate and operate a fan independently.

Step 8: Solder and Make Good Your Connections.

Take your soldering iron and solder ALL your joints, take care not to make any shorts when you solder the switch pins.

When you have everything soldered nicely then you _MUST_ tape all your joints with electrical tape, if you don't do this then the first time a +12v connection shorts to anything you will probably fuck your computer, or at least your PSU.

An optional extra step is to hot glue over the connections on the back of the switches just to make extra sure nothing shorts. I do this with pretty much every permanently assembled switch I use because I think its good practice. If your switch has an open assembly then be careful not to get any glue inside because it will probably break it.

Step 9: Make the Cables Nice

This is probably an optional extra but it will make your life a lot easier. I went over the cables with a load of cable ties (you could use electrical tape) and made them nice an neat, grouping together the 2 leads for each fan and making a bit of a snake out of the first 6 of cable so it comes out the bay nicely.

Step 10: Install the Fans

Mount the fans where you want them in the computer. I had to pass everything through an empty 5 1/2 inch bay to get it in. Make sure you rout the leads so they don't interfere with the other components.

I used the short fat little fan screw for 1 fan, but I didn't have any for the other so I used some little bolts that were just long enough to pass through the fan and the chassis. In my box the powerful fan blowers over the CPU / RAM and the quiet fan blows over the HDD's. I had to drill some vent holes in the plastic cover on the front, but most cases I've seen have holes here allready.

Step 11: Finished!

Sit back and enjoy!

I've got a little hand held label printer so I knocked out a pair of labels for mine. The HDD fan is quiet so I leave it on most of the time. The "CPU BOOST" fan (as I've taken to calling it) is noisy so I only us it when I'm doing something like transcoding or burning loads of disks (to keep the optical drives cool)

TBH you would probably have been better off buying a bay mounting fan controller, but I like having big red doom switches on the front of my box. I may get one of them flip top switches and make a reset button.

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    5 Discussions


    10 years ago on Step 2

    Could you use a potentiometer instead of the switches?


    Reply 10 years ago on Introduction

    I'm afraid not mate, well you could but seeing as how a small pot would have an impedance of say 0-10k and the fans are running off several 100mA @ 12v the range of impedance over which the fans would actually spin (say 0 - 100 ohms) would only be a tiny fraction of a turn of the pot. You could rig up a very simple PWM sort of thing using a 555 timer(s) and a pot for a £1 or so's worth of bits. There are plenty of examples of this sort of thing on the net.


    11 years ago on Step 11

    looks like you used some switches from radio shack, in fact, i have one of those illuminated switches, and one of those "doom" flip top switches, i use it in my jeep for the extra trail lights, people that havent ridden with me before always ask, and i tell them its a harpoon gun activator