Aug 252010
4 Pin PWM Fan

I was looking for something fan-like to move some air around, specifically from under my desk at work as it gets too warm there. It’s nice in winter, but unwanted in summer.

I was looking into this which needed a 50 Euro power control module and of course a propeller. And it would create about 100W output. Cool stuff, but overkill. Of course a simple small fan for 1000 Yen would do the trick, but where is the fun in that.

In the end I found this most simple method: a normal 4 pin PWM controlled fan as computers use them. Needs 12V DC, returns 2 count/revolution and can be controlled via a simple 5V signal. Can be easily controlled by an Arduino, and it can be programmed as I like (faster/slower, depending on time, temperature). Sounds like fun and useful at the same time!

Now let’s see if I can assemble it before it gets winter…

Aug 062010
USL5P - It still lives

I bought one of those some time ago (about 2005). It’s basically a small computer with a funny CPU (SH4, 266 MHz), RAM (64 MB) network (Fast Ethernet) and 5 USB 2.0 ports, 4 buttons, and some LEDs. Inside is a CF card for the OS, and originally you are supposed to connect USB storage devices which are then exported via Samba. Since it was basically a LANTANK with the internal IDE disk(s) replaced with a CF card, it did not take long until it was hacked. All you needed to do was to take out the CF card, modify some files (e.g. set a root password and enable telnet), and put it back. Suddenly you had a cut down accessible Debian. At first I used Gentoo (specifically from here) but when Gentoo broke on my desktop (trying to replace the shared glibc with another, newer and incompatible one on a running system is bad), I jumped to Ubuntu (Kubuntu) on my desktop and and plain Debian (or Ubuntu Server) on my servers.

So some month ago I updated it to the latest Debian release (unstable/unreleased) as the previous installation was from 2007 and updates were no longer available.

Here some pointers where to find useful information about this device and how to configure it to be on Debian sid/squeeze:

/etc/apt/sources.list should contain:

deb unstable main
deb unreleased main
And if anyone wonders why I would use such a slow machine: It runs on 5V, using max 2.2A (and that’s mostly for the USB ports which can draw 0.5A each). It also has no moving parts, it’s really small, and it just works (mostly thanks to Debian’s SH4 port). And it can do anything Linux can do when it comes to networking and USB.
To put some numbers to the “slow”: compiling a recent Linux kernel takes 8h.
A more modern similar machine would be this.