"Andrew Mawson" wrote in message
...

"Andy McKenzie" wrote in message
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"Andrew Mawson" wrote in
message
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"Andy Hall" wrote in message
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On 2006-07-26 08:34:18 +0100, "Andrew Mawson"
said:


"Keith D" wrote in message
...
I would like to have a data logger that can track the KWs
being
used
in my
home. I need to know load times/days etc. I have seen a number
of
items that
do this by attaching to the power cable from the consumer unit
and
then
sending this data using RF to a display unit.
(http://www.electrisave.co.uk/) but this does not have a PC
interface so I
cannot use it to log data over a long period of time.
Question: How does this device collect/measure the total
electricity
used?



I have a secondary elctricity meter (that was originally a coin
operated one) that has had the coin mech taken out and a
slotted
LED
sensor put on the disk, which via an optoisolator drives the
interupt
bit of the parallel port. I've been logging electricity (and
water
too) using this method for over 10 years now.

AWEM

Interesting. One interrupt per revolution of the disk?






Yes, and I use a simple RS transducer to give me water rate usage,
though that has to have a 'divide by 100' circuit in series due to
the
rapid rate of revolution. The software (which I wrote) does simple
zone control on my central heating, and also has provision to
monitor
gas, but I've never found a suitable sensor.

AWEM

Could you rig up an optical sensor that looked directly at the
digits on the
companies gas meter. It wouldn't have to actually read the numbers,
it could
just log movement of the last digit (thinking of my gas meter that
has an
'odometer' type display)? Although thinking about it a webcam with
character
recognition could take periodic snapshots of the gas meter

Andy



I held back from that approach as it could scare the pants off meter
readers ! The normal gas meter 'breathes' with a bellows, and can be
distinctly heard. I had indended to make a microphone based system
with filters to pick out it's distinctive sound, but like so many
things never got round to it.

AWEM

If you used a laser mounted on the wall opposite the meter the meter reader
should only notice a small burning sensation if he keeps his head still for
more than a minute!

Andy