Measuring power consumption

A recent electricity bill has prompted me to investigate how much power is being used by each device in and around the cabinet in the hope of figuring out what can be replaced to reduce running costs. I’ve had a power monitor from Maplin for a while, but most of the time it’s been monitoring total power consumption of the rack.


  • UPS: ~50W non-charging


  • 24 port 10/100 switch: 25W
  • 4 port 10/100/1000 switch: 18W
  • 5 port 10/100/1000 switch: 8W
  • Router: 3W
  • Modem: 3W


  • Boron (fileserver): 150-190W
  • Aluminium (desktop): 250-295W
  • Barium (HTPC): 66-85W

The audio system components haven’t been measured yet because at the moment they aren’t ready to drive a load and measuring the idle consumption wouldn’t be very meaningful. The amplifiers will be switched off when not in use and won’t be used that much compared to the items listed above.

Based on the data above, I have replaced the 3 switches with 1 switch. I have been investigating replacing boron with a collection of NAS devices for storage and a low-power ITX-based machine for services such as DHCP and DNS. However this is currently quite an expensive option.

Aluminium is a gaming-spec PC so will always consume quite a bit of power, however I’ve got some software under development which should mean that I won’t need to keep it on to download the occaisional torrent – that job could be offloaded to boron or my hosted server.

Barium is only on when I want to watch a DVD, a video or recorded TV from MythTV. It was specced to be quiet and consume as little power as possible with a Core 2 Duo CPU, 1GB DDR2, a passively cooled HDCP-capable VGA/DVI graphics card and a quiet PSU.

I’m going to continue to look at reducing consumption not just in the rack but around the rest of the house.

Serial port problem solved

Thanks to the chip manufacturer of the cheap serial port card, I’ve managed to get some extra serial ports working. If you can’t figure out how to get additional serial ports working, I recommend this guide [ZIP, 792KB] available from the Moschip driver download page. It should be valid for most models of serial cards, and explains how to add more than the standard 4 ports that most linux installs have.

Now that this problem is out of the way I can continue with writing the remote control software for the audio system.

Serial port problem part-way resolved

Having put the 4 port serial card back into boron, the onboard port now works again, so I’ll probably continue with developing the software. The expansion card still doesn’t work though, so I’ve ordered a cheap 2-port card from eBay in the hope that a different card will work.

Before reinstalling the card I upgraded Ubuntu to see if that would help (it didn’t) which brought its own scary moment of the 1TB RAID volume being dead. That too is solved now – the drive letter assignments had changed.

Hitch with the audio system

Today I started development of the software to control the whole-house audio system. It’s written in C# and based on the MiniHttpd project – a small but powerful implementation of a web server in C#.

However, when it came to testing the first bits of code, I’ve envountered a problem. A while ago I bought a 4 port RS232 serial card to go into boron, because the motherboard only has 1 onboard port which isn’t enough for the UPS, the matrix switcher and probably some other things such as connections to network switches.

The new card shows up fine in lspci, seems to be ok when running setserial -gb, but when trying to send or receive data nothing happens. Thinking it might be a conflict with the onboard port, I went into the BIOS and disabled it. Still nothing. So I swapped the card into another machine and re-enabled the onboard port in boron‘s BIOS. Now the onboard port doesn’t work either.

I’m going to contact the manufacturer of the card for some help. But for the onboard port I’m completely stumped. It too shows up in lspci and setserial -gb (though only when running using sudo, which wasn’t necessary before) but any attempts to use the port result in various I/O error messages. I was worried that the new card may have killed the serial communication capabilities of the matrix switcher and the UPS, but I’ve confirmed that at least the matrix switcher still works by connecting it to my test machine, iron.

If anyone thinks they might know what’s getting on, please get in contact via the comments for this post – I would be very greatful for any help.

Successful test of audio over CAT5

I have just successfuly tested transmission of near-line-level audio over the cat5 cables I’ve recently finished installing.

DAB Radio

The amplifiers and matrix switcher have been installed for a while, but until now I’ve not performed any tests of sending audio from one part of the house to the matrix switcher, through the appropriate amplifier and out of the installed speakers.

Green 2m CAT5 cable

I bought some 2m green cat5 cables off of ebay, but rather than use them as normally intended I cut one of them into two equal lengths.

After removing a length of the outer insulation at the cut ends, I attached 2 phono plugs to one length and a stereo 3.5mm jack to the other (with a little help from wikipedia for the correct pinout of the latter).

A multimeter was used to verify that there weren’t any shorts – wire-wrapping the connections was a little fiddly – before I plugged the cables in for testing.

Jack connected to DAB radio

The length with the phono plugs was connected to the matrix switcher and the RJ45 patch panel, and the other length was attached to the headphone output of a DAB radio in the kitchen and one of the 2 ports in that room.

Patch panel connection

The successful test is promising for the completion of this project. I have ordered and bid on 2 more sets of speakers for the dining room and kitchen, and the final amplifier will be ordered soon.

The software needs to be written to control the system, but I could probably do most of that in a weekend. A little more hardware in the form of a touchscreen capable low-power computer and an iPod Touch will be required to run the web-based front-end for the software. Then the system should be complete.

Look out for a video demo of the system once I’m happy with it!

Completing the data wiring


Today I added the final 4 network points – there are now a total of 24 around the house.

The wiring project started about 14 months ago, with the plan to have at least 2 network points in all rooms except the bathroom. The final distribution has ended up as:

  • Living room: 6
  • Dining room: 4
  • Kitchen: 2
  • Pantry: 4
  • Landing: 2
  • Bedroom 1: 4
  • Bedroom 3: 2


Despite considering that 24 ports might be a little excessive, I’ve come to realise that 24 ports isn’t quite enough especially when it comes to distributing analogue audio & video over CAT5 (i.e. not as IP data) since at least one port is required for each A/V combination depending on the quality of the signal desired. The living room should probably have 4 more ports, the kitchen could do with at least 2 more and a couple by the front door would come in useful for security purposes.


I’ve learnt a lot from the experience of doing this wiring, such as how to lift floorboards, that lathe & plaster ceilings are extremely fragile and plastering is nowhere near as easy as it looks.


Running the cables before moving in was certainly a good idea. It would have taken me probably another 12 months otherwise to get to this stage. It’s taken a lot more work than I expected, although the overall time is down to being in a lazy, bored and/or apathetic mood most weekends. I’m glad I did it though – the ports have come in useful for the MythTV system, for the family computer and soon enough the whole-house audio system. I’m also using them to trial some IP video cameras.



Monitoring power via my UPS

I’ve set up a few MRTG config files and some simple shell scripts to graph the available data from my Compaq UPS via Nut. This will give a basic way to monitor the combined power consumption of everything that’s connected to the UPS. Currently this is everything in the rack plus the computer under my desk (and the peripherals on top). If you like graphs, you can see them on this site.

In addition to this method, I also have a plug-in power meter that can be used on individual items. It’s currently plugged into the incoming side of the UPS. For whole house power monitoring, the Wattson looks pretty good, but it’s not exactly cheap.

Fire Protection


For quite a while now I’ve had 2U at the top of the rack consumed by an APW Fire Protection Unit. This clever bit of kit, found by chance on eBay for £15, will extinguish a fire using FM200 gas (with some nitrogen thrown in) when detected by either of it’s two optical smoke detectors.


Until today it hasn’t been plugged in for more than half a second because the alarm appears to be broken inside (or I need to do some sort of configuration which isn’t possible without a manual) and so it was far too noisy to use. The alarm is deafening and certainly does it’s job, but is obviously a little eager to make itself known. Just in case this was an indication that the gas might be released I disconnected the fillament in glass stopper on the end of the canister (later reconnected when I was happy it’s only the alarm that is broken).
To solve the alarm problem I have been forced to snip one of the wires to the sounder so that I can use it. This shouldn’t affect the operation of the unit, though it wont be able to give any audible indication of a fire. There is a visual indicator on the front to back it up. To replace to the audible function I will install a standard household smoke alarm.


I’m just waiting for a backup to complete before I hand over power management to it. In the event of a fire, it will instantly cut power to anything that it feeds, which in this case will be most things that are connected to the UPS. Unfortunately the UPS shutdown functionality isn’t compatible with my UPS since it uses basic status signalling, so if a fire does break out it had best not be in the UPS.

Getting NUT working with a Compaq T2400h


Several months ago I posted some information on the cable to connect a Compaq T2400h to a standard serial port. This weekend I finally got around to trying out the information that I found. I now have the 2.4KVA UPS at the bottom of my rack cabinet talking to my Ubuntu-based fileserver, boron.

The first step was to create the cable. This requires a 9 pin female ‘D’ connector and a matching male connector. For the cable I used an offcut of CAT5, though normally serial cables do not use twisted pair (usually just parallel wires).





The software part is done using NUT, for which there is a package included in the Ubuntu distribution. This software talks to the UPS, monitors it’s status and allows other computers to check the status. The monitoring applications are then responsible for shutting down the computers attached to the UPS should power fail and the battery become critical. So far this is just boron and my Windows machine, aluminium. The latter uses WinNUT to shut down Windows when needed.

There were a few problems getting NUT to work with Ubuntu. First off, the package doesnt put any configuration files in the /etc/nut path, so I had to go hunt for the examples and copy then modify them. The next problem was with permissions for the serial port. For testing purposes I tried running the protocol module as root, but this introduced different permissions problems. The solution was to add the ‘nut’ user to the ‘dialout’ group, which is one group that has access to the serial ports. To my relief this got everything working.

These are the parameters that I can access over the serial connection:

simon@boron:~$ upsc compaq@boron
battery.charge: 97.22
battery.runtime: 1620.000
battery.voltage: 0055.50
battery.voltage.nominal: 0048.00 upscode2
driver.parameter.input_timeout: 5
driver.parameter.manufacturer: Compaq
driver.parameter.port: /dev/ttyS0
driver.parameter.use_pre_lf: yes
driver.version: 2.0.5
driver.version.internal: 0.84
input.voltage: 0244.50
input.voltage.maximum: 0276.00
input.voltage.minimim: 0162.00
input.voltage.nominal: 0230.00
output.current: 0001.95
output.frequency: 0050.00
output.voltage: 0215.10
ups.delay.reboot: 000
ups.delay.shutdown: 000
ups.load: 21.875
ups.mfr: Compaq
ups.model: UPS 2400 VA FW -0023
ups.power.nominal: 2300.000
ups.serial: E########
ups.status: OL TRIM

These are the resources that I used to get the UPS/NUT combo working: