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
Digikey Search catalog for Current Transducer or Current Sensor
AC Line Voltage
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
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)
