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Rack box project

From CaveLab
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This project was terminated when I moved out of my first apartment.
Rack box 13. April 09

A server rack box filled with electronics and microcontroller modules.


When I was young and single I had a lot of spare time. I lived in a tiny apartment and wanted to build electronic modules for home-automation and whatever really. I just wanted to solder and make circuit boards. So I got myself a server rack box, and started making electronics and microcontroller modules to fill it with.

Pretty much all electronics I built between 2005 and 2010 went into the rack box project. A lot of it was just to supply and monitor voltage levels, temperature, fuses, alarms, etc inside the rack box itself. But it also included a fair amount of home-automation stuff as well; things like lights, heat, intruder alarm etc. The rack box is a 19" standard server rack box, constructed in steel. It was fed 220V to four power supplies inside, providing 5, 12, 13.8 and 24 volts. Without anything special going on the box drew about 13 watts. Power was supplied from the UPS, so it would stay when in the case of a backout.

All fuses, power supplies and modules were monitored and an alarm would sound if anything failed. A lot of the modules inside were used for this purpose alone, and was one of the reasons why I built the thing in the first place. I wanted something to monitor :) The rack box connected to the outside world through four d-sub connectors, but it also had RS232 serial cables going to my computer.

Since the box didn't have any airflow, and a lot of electronics inside it got warm. I built a fan and temperature controller to monitor the temperature, start a fan if it got hot and sound the alarm if it got even hotter.

In case something really bad happened the box also has an emergency shutdown function, that cut the main 220V supply to the system. It could be triggered automatically from inside the box or the status panel, I had a lot of ideas for automatic shutdown in the case of fire or extreme heat, but I never got around to it. The emergency shutdown controller had it's own isolated power supply, connected directly to the UPS.

If anything went wrong a stacklight would flash, and a sound alarm was sounded. This could be pretty annoying, especially at night. That's why the system had a mute function, which turned off all audible alarms. This was automatically enabled at night with a timer.

Since the whole system was connected to a UPS, there wasn't any way to detect a 220V main failure. So for that purpose I had a tiny AC adapter not connected to the UPS power a relay. Using that relay the system was able to detect if it was running on battery (the UPS) or the 220V main.

At the end, as you can see in the image gallery the rack box got really crowded, so I eventually began making stand-alone modules what would be placed outside the box with their own AC adapters and voltage regulators. Their signals still went via control cables back to the rack box though.

The project ended when I moved out of the apartment in 2010, I removed all modules and electronics and got rid of the server rack box. I still have most of the modules, and are rebuilding and reprogramming them for other purposes.



The rack box alone without any alarm, lights etc. has a power consumption of 13 watts. When the stack lights or the interior light is on the power consumption rises to about 20 watts. The rack box is protected with a net filter and a UPS, the UPS prevents the system from going offline if a power loss occurs.


An external 12V power supply is used for detecting total power loss, meaning that the system is running on battery backup (UPS).

Rack status panel

Rack status panel has LEDs for pretty much every situation that can occur in the rack box. Lights, alarms, fan, mute etc. can also be controlled from the panel. Emergency shutdown can both be triggered and reset from Rack status panel. It's made of a desk box with a aluminum front plate, this is stiff and provides and does not bend when buttons are pushed.

The panel is connected to the rack box using three contacts, one 9-, 25- and 37 pins D-sub cable. If one of the cables are disconnected or the fuse burns out the alarm will sound, the panel is monitored by Multi-purpose module 1. Digital emergency interface module is installed inside the Rack status panel and connected to the computer using a DB9 serial cable. All voltages (5, 13.8 and 24) is available via lab plugs. The alarm (Alarm unit) can be activated/deactivated using the key. When the alarm, or away mode is active all LEDs are turned off and none of the buttons work.