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Gina

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Everything posted by Gina

  1. Thanks for your reply. No.1 is definitely possible and a good idea once I've built the new enclosure. I thought of No.2 but it's more complicated and the desiccant would want replacing pretty often. No.3 doesn't apply because disassembly is a requirement.
  2. Been watching a science programme on BBC4 which mentioned the Challenger Shuttle accident and the cause, which turned out to be freezing cold weather affecting rubber O rings. Now I wonder if frost was the reason my ASC seals failed. Bathroom sealant is used at room temperature and not designed for large temperature range, particularly cold.
  3. Looks like you could run your whole household off those!!!
  4. Camera housing base - thermally insulates the camera from the waterblock. Square hole takes the Peltier TEC.
  5. Camera housing for thermal insulation. Shown in transparent blue.
  6. The new design will use the 4" dome to give enough room for the dew heater resistors. With the outer casing being sealed there is no need to seal the camera housing - just provide thermal insulation.
  7. Just realised I have the answer all along - I have water cooling and the waterblock can cool the RPi as well as the hot side of the TEC. At first I thought of an aluminium box for the RPi but then I realised that would stop the WiFi from working I can put the RPi below the camera and cool air from the waterblock can descend onto the RPi by convection. Now to redesign the enclosure...
  8. Wearing my Heath-Robinson hat, the question of internal temperature could be overcome with a Peltier TEC and inside/outside heatsinks and fan(s). Cooling the internal air when too hot and warming it when too cool.
  9. It's a cross-section drawing except for the dome. Well, I say "drawing" with tongue in cheek! More a sort of "artist's impression" by a failed artist. The dome isn't over the telescope so no views would be available (or very restricted).
  10. I'll try it - thanks. Ordered a tube. Also ordered some ceramic 5W resistors for the dew heater. I think the seal I made for the cables worked alright but I may put the RPi inside the casing and then I shall only need power, which is easy to seal. I was worried about high summer temperatures (ha ha) with the unit in full sunshine (if we get any) but I think an external shield spaced away from the main body should take care of some solar radiation. It would be open top and bottom so convection can take heat away. Of course, the dome would be in direct sunlight.
  11. Just tested the top of the case that was sealed and found a leak. That part was not as well sealed as the other parts.
  12. Hmm... that's what I thought and it was oozing out everywhere. I wondered if it was actually waterproof.
  13. I think proper O rings or 3D printed TPU sealing rings would be a much better bet than silicone sealant. I need to change hat from botcher to engineer!!
  14. It was failed sealing that caused the problem with desiccant to dry ordinary air. Maybe I should re-examine my sealing method - I relied on silicone bathroom sealant. For the few days during which the casing stayed sealed and the air dry, the ASC worked perfectly with the water cooling. Except it needed a bit more than the 2W dew heater I was using - that is not a problem.
  15. I used DPC between the main beams and six concrete foundation blocks.
  16. Print failed. I'll see what tomorrow brings...
  17. 3D printing the casing. About 3 hours left. Rather than directing all the warm air up and out of the dome, I shall have holes in the base plate and let some escape out the bottom. The idea is to maintain a reasonable airflow over the heatsink fins for best cooling.
  18. -8.5°C and it's been there for a while now. Just added a barrier to restrict the airflow from one side of the cooler to see how much it affects the cooling. Went down a bit more but now on the rise and back to -8.5°C. A bit later -- Seems steady at -7.6°C.
  19. Shut down and powered off and removed the TEC1-12706 leaving just the smaller Peltier TEC running at 12v. Camera temperature has got down to -7.8°C and still slowly going down. Conclusion - the TEC1-12706 is not suitable for this application (though it worked for the dehumidifier). Nowhere near the -20°C I got with water cooling but not bad. Restricting the airflow a bit by directing some up into the dome may reduce the cooling a bit but we'll see.
  20. Running a test with stacked TECs but it's not good! First of all the temperature gradually dropped to around 2°C then rose again to 5°C. With the single 30x30mm TEC it got down to -2°C. Running at 11v and just over 5A. This is very disappointing. Mind you, it is using a lot of power (over 55W) whereas with water cooling the TEC runs on 20W and then there would be some power wanted for a dew heater but I doubt it would want 35W!
  21. Now I need to work out how to vent the warm air to the atmosphere whilst stopping rain coming in when the fan isn't running. I'm thinking a cone to direct the air into the dome via the camera and out round the edge of the dome and an outer cone (maybe the cone shaped top of the casing with a smaller cone inside. With just the 30x30mm TEC and air cooling albeit blown by a fan, I think the cooling may not be enough. I could use a double stacked Peltier TEC cooler using the TEC1-12706. This would take more power than water cooling but provides warm air for dew prevention. If I use water cooling I would need to add a heater which seems daft. Plus the air cooled system might not be much less efficient once dew heating is taken into account.
  22. I may have a new name for my ASC - "An OriGinal All Sky Camera"
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