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Gina

Beyond the Event Horizon
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Everything posted by Gina

  1. Yes, I remember reading that. I don't think there's any doubt that I can get the humidity low enough. Next thing I'm working on is the cooling. Now where's that 1100D with the cold finger hiding???
  2. With the box sealed and 8 bags of silica gel in it the dewpoint has now reached -10C after 30m. It is still slowly going down so I'm hopeful of reaching -15C in time I think this will be quite sufficient. In my tests a year or two ago I went down to -20C but the noise reduction between -10C and -20C was small. I am now content that I can achieve low enough humidity - next I need to perfect the machanism for replacing the cover glass within the dry box. It may not be necessary to use that many bags - the main point will be to reduce the amount of free air. In that way the amount of moisture in the box after closing the lid will also be reduced.
  3. A small advance on the cover glass replacement mechanism design. A soft sponge pad connects the cover glass to a flat piece of plastic or metal which in turn is attached to the shaft. If I don't have the 3D printer I plan to use a sleeve on the shaft with the flat plate glued to it. If printed in plastic this can be all one piece - a tight fit on the shaft. The pad, placed in the centre of the glass will provide equal pressure all round the edge to ensure it sticks well, allowing for a slight misalignment.
  4. There may be a slim chance of imaging tonight - keeping fingers crossed I shall do my best to try and provide as reliable a method as possible - I realise that others may follow my example and the responsibility this entails
  5. It seems that after an hour the RH has stabilised at around 15% at 20C giving a dewpoint of -7C. I think the limit may be due to the fact that there is currently a gap where the wires to the DHT22 go past the box top seal. I shall have to seal the box before any futher testing to be meaningful.
  6. A bit later and the humidity is getting back to where it was but with a lower temperature.
  7. You may be right but I opened the lid in the living room and changed the air and immediately got RH or 47% at about the same temperature when the lid was back on. I think the silica gel held the temperature.
  8. Not true actually - RH = 74% for air from freezer Living room RH = 43% according to my wal thermometer and humidity meter.
  9. Thought I'd try an experiment so I unplugged the USB lead and put the box and Arduino in the freezer for a while. Then brought it back into the living room and reconnected to the PC. Here are the results for the first 15 minutes. This shows how the dew point depends on temperature as well as humidity.
  10. Oh yes, I think so. However, this is with just two silica gel bags and I shall put as many in as I can. If I can print the parts I can arrange to keep the bags away from the mechanism - barriers with holes in. Here's a screenshot of the serial output with another couple of bags added.
  11. I've set up a drying test with the box, DHT22 T & RH sensor and Arduino. Here's a screenshot of the first few minutes of drying and a photo of the setup.
  12. Here are a couple of screenshots from SketchUp showing the idea. Front side of box removed for clarity. Also, I haven't shown the grommets or the box details. This is just a rough sketch but it is to scale. The arcs show the path of the cover glass as its fitted onto the sensor frame. The shaft shown is a 6mm aluminium rod but I may choose a different size depending on the size of grommets - I have quite a variety. I might use silicone grease on the grommets to aid sealing. I still have to work out how the sensor assembly will be held in the right place and orientation and also the lever on the shaft and attachment to the cover glass. It will be next week (or later) before I'm ready to replace the cover glass on the working sensor, as there's plenty to do before then so I might wait until I get the 3D printer working again. Then I can print parts with just the right dimensions, angles etc.
  13. Yes, I should think so I was thinking of mounting the lever on a smooth shaft going through grommets. With a nice close fit of course to make a seal.
  14. I'm still thinking about the lever - I have some ideas but not decided yet. I may do a SketchUp model. Trouble is SketchUp doesn't cater for a moving model AFAIK. Also, I don't know when I'm going to get the replacement control board for my 3D printer so I may have to build it the hard way. The sort of thing I have in mind is to hold the sensor assembly with the sensor facing slightly downwards so that any dust doesn't settle on it. And the cover glass with the inside face also facing slightly downwards. Then the cover glass swung round and onto the sensor frame once the humidity has dropped sufficiently. We haven't had a fire for a few days now so I'm hoping the dust level indoors is suitably low
  15. Thanks They look similar to the ones in my kit but I've ordered one to see. Shold be here Friday or Saturday.
  16. I think I may have the answer to the glue problem - double sided adhesive tape. Placed around the frame of the sensor. Then the cover glass could be moved into position and gently pushed home onto the sticky tape. Likewise the cover glass can be attached to the lever with double sided adhesive sponge. With the adhesive sponge on the outside of the cover glass any residue can be easily cleaned off.
  17. I've sorted out a clear plastic box that I can use to dry the air round the sensor and apply the cover glass. This will also contain colour changing silica gel bags - of which I have plenty I plan to have a DHT22 digital temperature and humidity sensor also in the box with the cable going through a gland and connected to an Arduino to check the dew point of the air. That way I can be sure the air is dry enough.
  18. I'll try the the epoxy/IPA approach. I saw your post on page 74 and I've ordered those conical tools but the earlier link shows several options and I just wondered which of those you got.
  19. Have you tried using a dry tool on an 1100D sensor? These have a much tougher CFA than earlier models. I tried dry on a 350D sensor (I think) and the CFA came off eventually. I tried dry on the 1100D and even after about 5 mins continuous buffing the sensor was polished and very hot but still a strong green colour - no CFA had come off at all and the buffing tool was still white. Maybe the tools you are using are different, harder perhaps. I have some of the pointed tools mentioned earlier, on order from ebay and I'll see how they work. I can say I was surprised how even the CFA removal was with the paint scratch polishing paste - quite different from what I achieved manually.
  20. Still looking out the bits and pieces to make up the test rig. Can't find the Peltier TEC I was going to use - a 12v 3A one from Farnel and more efficient than the Chinese ones. However, I do have a 3.3v 2A one (TEC1-4902) about 7W I/P power and a 50mm square CPU cooler. I have that setup running now and the cold side has already collected a thick layer of ice
  21. Yes, but then it might run over the frame where the cover glass is going to go. Anyway, time will tell
  22. Back to the debayering... I have had a very very quick go at debayering the 1100D duff sensor with Dremel look-alike and felt buffing tool plus paint scratch repair paste. Here is a photo of the result. When I get the epoxy resin I can practice adding resin to the area around the sensor - see if I can cover the gold wires but keep below of the frame so that a cover glass could go back on when I work on the real job (a working sensor).
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