Carbon diet

It is called "Mountain top removal"

def: Mountain Top Removal

February 2006

I don't approve of people destroying Appalachia so we can heat our houses with electricity from coal-fired power plants. So I am putting myself on a low carbon diet.

Conservation begins with data collection

I have to establish a baseline of our current energy use. I will need to log electrical use and temperatures over a period of time.

My house uses gas (and optionally, wood) for heat. It has an electric stove and water heater. Only the antique gas/wood central furnace uses gas.

I can monitor its run time by monitoring the electrical circuits running to it. I don't have a good way to measure actual gas used other than gas meter readings. I suppose I could read the meter once a day and log it...

I can install a data logger and current taps at the main breaker panel to get readings on the whole house.

Current taps

I happen to have a couple split-core current sensors left over from my halcyon days at Coactive Networks. They are Magnelab Model File:Sct-0750.pdf-100 and they say "100A to .333v Full Range". I bet that means that when 100 amps runs through the cable, it puts out 1/3 volt DC.

From the datasheet, it puts out .066 volts at 20% or 20A in this case.

This is good for whole house. You put one around each cable coming into the breaker panel. 100A is a bit much for other applications though. I would like something in the 15 amp range (one circuit breaker)

You can buy direct from the factory; they are $46 each. If you don't need the split core feature you can get sensors in the $30 range.

Other sources

CR Magnetics

Digikey Search catalog for Current Transducer or Current Sensor

Data loggers

What do I connect my sensors to? A logger records information which can later be transferred to a desktop computer typically via serial port for analysis. Using a logger to buffer data means you don't have to have your computer turned on all the time to log data in real-time. You can leave it plugged in all the time, and just grab data when the computer is powered on.

Onset	Hobo	< $100	sells matched sensors including split core transformers
Pace Scientific	Pocket Logger	$499	expensive but full range of accessories

Remote locations

This won't work if your sensors are located up the street in another building. How can we move the data over a longer distance?

Dialup modem? Sure. Connect an external modem to the serial port and program it to answer the phone. This is fine if you still use modems :-) and have a phone line available at the remote site.

Network connection or WiFi connection - Well now, this could be where the WRT54GS project comes in handy. For around $60 and a little hacking I can connect a WRT54GS access point to the data logger via RS232 serial port, and it can then act as the bridge to the network via either its 5 ethernet ports or its Wifi port. In fact for this tiny app I could probably also just use one of my old USR2450 WiFi modules. They already have serial ports built in.

Measurements using Kill-a-watt

Computers

HP Vectra desktop

• Astec ATX90-3405 SFX/MicroATX power supply [1]
• HP Motherboard
• RAM

(SFX has no -5V supply so is not ISA compatible. 90W is all the spec requires.)

Via EPIA 800

• Astec ATX90 power supply

Board by itself draws 29W with this supply
Adding the CD drive, draws 3W more when drive checks for CD then drops to 29W
Adding the Vectra HD, draws 34W at boot and then drops to 22W, so the CPU must still be doing some work when it is unable to boot.

Spinning down the HD drops it to 19W.

What I'd like to do is load up a CF card with the operating system and have the hard drive hold only data, so when the system is idle the drive spins down.

Old blue ATX case

• Powerman 235W ATX supply with on/off switch
• Pentium Pro 200 Intel Mars motherboard
• Four 72 pin 32MB SIMMS = 128 MB
• No CPU fan (power supply fan directs air directly onto heatsink)
• Tulip network card (est 2W)
• Soundblaster Model CT4180 card (2W)
• Dual port Intel network card (3-4W)
• Dual port SIIG USB 1.0 card (2W)
• Trident video card (ISA) (3W)
• Intel Mars motherboard PIIX chipset
• PS/2 keyboard (no difference on power reading w/o keyboard)
• IDE hard drive: IBM Deskstar 15 GB IBM-DTLA-307015

Boot: 55-60W, peaks to 70W
Idle: 36W
HD spun down: 31W
Stripped down: MB + 128MB RAM + HD = 23 W

Spinning down the hard drive saves 5 watts

Power supply has OFF switch; with the various and sundry network cards installed it burns

PS fan and CPU fan died years ago so I put the high quality fan from a Sun 3 workstation into the supply and dumped the CPU fan. CPU does NOT get hot under normal operation.

CDROM drives

Only needed occasionally; I can leave a drive in the system but unhook power to it.

• Diamond 8X CDROM: 1 W when idle (no disc in drive)