Here's a simple DIY fan switch. I've seen this technique used in SPCR forums before, so it is in no way an original idea. Given the number of questions about fan controllers, I thought it might be useful for others to see how easy it is to make their own. The whole thing cost me about $5 and took half an hour to make, even with my crude soldering skills. The 12-position switch provides voltages from 12V down to about 3.75V, which should cover most requirements. The diodes used are 1N4004 which are easily available and are rated at 1A, so there is no fear of overloading anything. I think any diode from the 1N400x series would be fine. Positive 12V is applied to the silver wire at the bottom, and the positive terminal of the fan is connected to the red wire which has been soldered to the pole of the switch. Note that the diodes are all facing in the same direction, with positive applied to the anode, which is the end without the silver band on it (important!).

Each diode drops the voltage by about 0.75V, so you can make up whatever combinations you like, eg a simple toggle switch with 6V and 4.5V positions, etc.

If you're just looking for a safe way of getting just under 7V, you can simply join seven diodes in series without the switch, or 6 diodes will give you about 7.5V. The diodes only cost about 5 or 10 cents each.

To all of you who have made something similar, do you guys do anything to protect those leads from touching the case?

I've made a few of these. Once, one of the exposed leads of the diodes touch my case and shorted the PSU and fried my motherboard.

Zalman Fanmate II only costs $5 if purchased seperately. Zalman CPU fans normally comes with one. After turning on Cool'n'Quiet and undervolted my A64 3000+ to 1.1v, I no longer need it for the CPU fan, so I just connect it other fans.

Also, you probably have some onboard fan controllers and you don't even know it. Click the link below to see how to use them with SpeedFan.

http://forums.silentpcreview.com/viewtopic.php?t=24846

I do have some fanmates.

However, these custom made volage controllers are very nice because they are relatively load (current) independant. So I can hook up 4 case fans in parralel etc, and still get predictable results. The Zalman fanmate's ability to control speed and heat generation is dependent on what kind of an you connect to, and if you connect to something that draws a large amount of current, it cannot handle that very well.

I have a server rack cabinet with 4 computers and a total of 15 various fans to control.

Anyways, who else out there are using this type of voltage controllers?

Wow, that's pretty scary looking... as compact and simple to build as it is, I'd personally really prefer to just solder all that to a pre-drilled circuit board instead.

If you're going to have exposed leads you can always try slipping a chunk of heatshrink insulation over the wires before you solder it. Either that or I suppose you could brush on a bit a liquid electrical insulation tape, which you can find in various hardware/auto stores and places that sell wiring stuff for trailers.

I don't think a Fanmate will go as low as this, also you can design the controller to go even lower if necessary. About 2 inches of standard electrical tape will take care of any concerns about shorting. As for it looking scary... well I suppose it does. At the time I made it I didn't have my wire cutters with me, so I couldn't clean it up as nicely as I would have liked. It is, however, very robust. A circuit board would complicate and add expense to what was intended to be a cheap and easy project. While to some it may not look so good, point-to-point wiring is quite commonly used by audio fanatics to minimize signal path lengths, for example.

I've never made anything quite like the above, but if I WERE to make something like it, I'd probably use Liquid Electrical Tape