Remote control for server power supplies


For the reasons given below (safety and certification), I give up this project. If I ever need such a device, I will try to find a commercially available one instead.


I have several systems in my personal computing center (a noisy room at home, that is), and want to switch them off and back on remotely.

As I also have a terminal server with 16 serial ports in there, I am planning to build a device that has a serial (RS232) interface connected to that terminal server, and a bunch of power outlets on the other side which can be powered on and off through serial commands.

A small microcontroller board, a relay and a nicely crafted firmware for the microcontroller should do the job...

Security features such as powering off all ports in case of a power outage and defaults for all power connectors to "off" to prevent them from running e.g. when I am not at home but a power outage had occurred, must also be implemented.

Safety certification is beyond my financial possibilities, I have now found out (several thousand Euro), so it might be that I give up this project due to insurance problems. There are solutions like this commercially available.



The device will follow a modular design: There is one control module, which is where the serial interface is connected to an input device (such as a computer's serial interface, or a terminal server). To this control module, up to three switching modules can be connected, which is where the power plugs are located and the actual switching takes place. Furthermore, multiple control modules can be connected to each other, then acting as "master" and "slave" modules, where the "master" module is the one with the serial attachment, and the "slave" modules can act as additional switch banks.

User interface

The control module will have a command line based user interface.

First of all, the available power plugs are addressed as RLYxy, where RLY stands for "relay", x is the bank number, y is the plug number per bank.

The user interface asks for commands by displaying a command prompt consisting of a unique identifier of the control module, and a > character, e.g. "pc.A1-001>". Commands are entered as described below, terminated by the return key.

Available commands are:

In these commands, y can be replaced by 0 to address all plugs at one switching module at once. If both x and y are given as 0, all power plugs on all switching modules attached to the control module are addressed.

Commands can either fail or succeed. In case of success, the system prints "ok" before returning to the command prompt mode. In case of failure, it prints "failed:" and an error code, e.g. "failed: E-A001.", and returns to the command prompt, if the error was not fatal.