Introduction

From time to time we receive some of the craziest requests in our [M]ailbox, so goes the tale about a young fellow who wanted to use up to 20 fans inside his computer. Frowning my eyebrows I did not question him further since I know this fellow has an extreme way of living, instead I went on thinking that maybe some of the older ATX PSU's I have around might proof to be of good use. Now few months later I'm ready to share with you the [M]axtreme Fan Controller, nothing but an ordinary ATX PSU.

To start with I was first thinking about using a linear type of power converting; with the LM338 you have a powerful linear regulator which can regulate 12V down to 7V without a problem. It wouldn't be too hard to build since these regulators demand very little extra components, and since the circuit is so small in size it would require less time and research for me to get the extreme fan controller done. Downside there is that when using a huge bunch of fans at 7V would set a large voltage drop over the regulator and thus forcing it to heat up quite a lot. Large current drawn will most likely force me to use 3 maybe 4 of those regulators in parallel and thus making the total circuit not only large but also harder to cool down. Plus, more heatsinks and more components to buy so the costs would increase too.

Next stop was getting one of those Velleman PSU kits, but looking on their site I noticed that they don't seem to be powerful enough for our application.

Then I remembered reading an article that explained how to make your ATX PSU output 24V. Aha, we can modify ATX PSU's right, just look at how OCZ once brought out there famous PowerStream series which allowed volt lines tweaking. I started hunting down the article which comes with a basic circuit description and in no time I saw a solution on how to make on ordinary ATX PSU into a powerful 12~0v fan controller. Between all the other electronics which have been collecting dust in my testing laboratory - aka kitchen - I took one of these noname 300W ATX PSU's I somehow had gathered over the past years, this little fellow was powerful enough and yet small in size compared with linear power supplies of the same rating.



Unfortunately, things didn't really go as easy as first thought. This article will include all the build in safety checks I had to get around, I hope some of you will understand what I'm going to explain here today, if not you still have the possibility to see the results of my experiments.

Before we go into all the technical stuff let me give you one last warning, when modifying ATX power supplies you are working with an electronic device which is at one side connected to the mains. Always be cautions with what you do and if you don't really feel comfortable with what you’re doing then I suggest rather staying away from it and letting a professional do the modifications for you. You can harm yourself pretty easily, use common sense instead!

For this how-to I used an ordinary no-name 300W ATX PSU an older generation. Grey box, nothing fancy, excellent for our modifications to test around with:



Now fasten your seatbelt, this trip will prove to be quite an adventure for most of you ->