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  1. #221
    Quote Originally Posted by Clive S View Post
    Thanks for the feedback. But it also states this

    "Bear in mind though that there is no international standard for stating COPs and therefore each manufacturer will state the maximum COP obtainable for their units under optimum temperature and humidity conditions. In reality you may not therefore always acheive the COP rating stated."

    I have been involved in installing a few heat pumps air source and ground source and I believe that they were in the region of about 3-4 to 1. My next door neighbour has had his gas taken out and put in an air source pump. I am very interested to see the results over time.
    Hi Clive,

    All I can tell you is throughout a season the total kwh used by the heat pump is is about the same or less than the 1hp water pump that is switched on for exactly the same time, I have clamp on current monitors on both going to the main energy logger in the house. The heat pump pulls about 2.9kw max and will bring 60m^3 of water from 18 to 28 degrees in a couple of days. Costs about £1k in electricity to run both per season. I have no experience of them in houses although a friend who has also just rebuilt his house is now relying solely on an air sourced heat pump for house heating with hot water boosted with immersion and tells me he is saving a fortune, but he wasn't on mains gas rather oil delivered by tanker which is expensive.

    What maybe of interest is I had a 10kw pump heating a much smaller 10m^3 above ground pool, this was the older generation pump without the inverter and therefore constant compressor speed / current draw. The electricity cost of running this unit was the same per season as the new pool system, therefore it must have been much less efficient.
    Last edited by devmonkey; 1 Week Ago at 10:23 AM.

  2. #222
    mekanik's Avatar
    Lives in Barrow in Furness, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 9-10 years. Has a total post count of 671. Received thanks 86 times, giving thanks to others 132 times.
    I looked into heat pumps several year ago, obviously ground source is the most efficient but due to my building plot this is not an option, max for air source is in the region of COP 5

  3. #223
    OK.I think I have hijacked this thread and taken it off topic sorry. But thanks for the feed back.
    The more you know, The better you know, How little you know

  4. As I said, the limiting factor on air-sourced reverse-cycle air con for heating is when the outside temperature is so low that the external heat exchanger freezes. In the UK I would expect you'd need some additional heating system for the coldest parts of the year (September to May in Cumbria if I remember correctly). In Perth (The Australian one rather than the original) we had a few occasions when the heat exchanger froze but but not many. A well insulated house obviously makes a big difference. It's been a while, but I think that unit used 4kW of electricity for the equivalent of 14kW of heating.
    Engineering is the art of doing for ten shillings what any fool can do for a pound.

  5. #225
    I have realised something about these sensors. They are colour sensors, and the colour detection is done by layering a grid of colour alternating RGB filters over the individual pixels which are all identical photodiodes (i.e. the pixel is monochrome) in what is called a Bayer pattern. These are laid out to match the human eye's response to colour, with 50% of the pixels green and 25% red and 25% blue. See https://en.wikipedia.org/wiki/Bayer_filter

    Click image for larger version. 

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    This isn't ideal as I'm using a red laser. This means only 25% of the pixels are useful and the sensor will be interpolating the values between 'red' pixels.

    Anyway someone pointed me towards some super crazy people in astrophotography who 'de-bayer' their very expensive DSLR sensors with a toothpick so the sensor becomes monochrome at its native resolution, effectively scratching off this colour filer layer to expose the raw sensor.

    I have just tried this procedure and ruined a webcam sensor (ripped it off the pcb) so I don't recommend it.

    The first casualty of this miss-adventure, don't think it is still worth £7 !
    Click image for larger version. 

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    Last edited by devmonkey; 6 Days Ago at 10:36 PM.

  6. I suspect this is not the greatest limitation on the acuracy of your system. Making the concrete floor of your shed more rigid should be a higher priority.
    Engineering is the art of doing for ten shillings what any fool can do for a pound.

  7. #227
    Quote Originally Posted by Kitwn View Post
    I suspect this is not the greatest limitation on the acuracy of your system. Making the concrete floor of your shed more rigid should be a higher priority.
    You may think that Kit, however I believe the (presumably linear) interpolation on the sensor is messing with my non-linear intensity fitting algorithms. It makes no sense to resolve down to sub-pixel resolution when 75% of the sensor information is estimated (Nyquist would have a fit).

    For example imagine the raw intensity at the peak of our gaussian laser line looks like this:
    100, 100, 101, 101, 100, 100
    Now if this falls under the bayer filter on a green+red filter line arranged as:
    G, R, G, R, G, R, G

    With only red laser light, nearest neighbour linear interpolation would look like this:
    100, 100, 100, 101, 100, 100

    If the bayer filter is offset 1 pixel the other way you would get
    100, 100, 101, 100, 100, 100

    Therefore you have 1 pixel (3um) uncertainty and this is for a green+red filter line. I think is worse for a green+blue filter line where all the information is interpolated, i.e the information rate is zero.

    I have some ideas to detect and strip this out but it is guess work without a datasheet for the camera chip, or maybe just reduce the resolution of the system from 1 pixel to say 4 pixels (6um).

    I have a few RPIs here with cameras which I can get the raw bayer data from and just use the red pixels (can't get the raw data from a webcam), might we worth an experiment but would need entirely new code.

    An alternative would be to use an IR laser as the bayer filter is transparent to IR therefore the sensor will behave as monochrome at full resolution, but then you couldn't see the laser for rough alignment.

    Monochrome usb cameras (that are made without the bayer filter) are expensive as there is no mass demand.
    Last edited by devmonkey; 6 Days Ago at 10:53 AM.

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