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  1. #21
    I got my sensors all wired up. Well all but one, I managed to pop one of the digital temp sensors. I will need to order another one. Anyway I ran a test overnight with the sensors in a closed container and logged out the temperatures from all 7 digital sensors and the 4 analog sensors that I can hook up at the same time. Here is the raw temperature readout.

    I then analyzed the data and calculated a new scale and offset that would bring all the sensors into a closer line with the first digital sensor. Here is the corrected data.

    And finally I worked out the difference between the reference sensor and the rest. The analog sensors lag behind the digital ones, probably because of larger thermal mass. That is why the error grows so large during times of fast change (sunrise). When the temperature is stable the error is within 0.2 degrees C. It is even smaller for the digital sensors, I may leave the analog sensors off or use them where direct comparison is not important.

    Last edited by reality_boy; 07-07-2019 at 10:39 PM.

  2. #22
    It has gotten up to 109 F here, very hot indeed! However my test house is holding up well. There are no signs of warping and there is only a slight discoloration on the plastic.

    I did notice that at the hottest time of the day the metal pole is heating up hotter than ambient temperature and radiating heat into the house. I suspect painting the pole white would help. On the flip side in a cold environment painting the pole black probably helps get heat into the house, even on a wooden rocket box. I did not measure this but it was quite warm to the touch, I estimate it was 8 degrees hotter than ambient.

    I have my temp sensors all set up, and I made a mount for my test houses. I just need to put the whole thing up and let it run. One problem is that we are only days away from the monsoons kicking in so we now have heavy cloud cover and should be seeing quite a bit or rain for the next few weeks. I really should have put this all up two weeks ago to catch the high point of summer heat...
    Last edited by reality_boy; 08-25-2019 at 10:22 PM.

  3. #23
    Life got in the way of this project and I have not been able to post here for a while. However I did manage to get some more work done on it. In particular I finished up my experiments using different colors of PLA. I have found that using black PLA and painting the outside white (or brown, as needed for your environment) provides the greatest light blockage. In addition I printed out some sample tubes using different color PLA and painted as needed. Below is a shot of the samples after spending a month in Arizona summer heat (over 115 F at times). You can see that the black PLA deformed just a bit, while the rest remained stable. I also checked by hand to see that the PLA was not softening up and it always felt solid to me. I'm confident that this material will survive the summer in Arizona, and therefor would make a good material for any region.

    I have been turning my attention to new ways to add texture to the interior of the bat house. I experimented with a lattus pattern and was able to optimize this to print in a continuous loop with no infill. However while it is very strong it feels very clunky to me. Next I experimented with the 'fuzzy skin' option in Cura, that adds random offsets to your print to create a rough texture on the wall. That produced a very interesting texture that while not quite rough enough to use without any sort of additional structure is still very promising. I started to go down the path of learning to code macro scripts in Fusion 360 with the idea of being able to selectively apply a fuzzy skin type effect.

    Last edited by reality_boy; 09-02-2019 at 03:21 PM.

  4. #24
    I have been struggling with serious under-extrusion on my Ender 3 for a while now. I tried changing out the extruder, swapping hotends, new PTFE tubing, cleaning the hotend, new nozzle, and changing the print temperatures by a lot, but nothing seemed to work. I suspected the extruder was not producing enough force, but blindly swapping out parts was not giving good results.

    Finally out of desperation I came up with a novel way to measure the force output of the extruder. Basically I pulled the nozzle off the hotend, blocked up the z-axis so it could not move up, and extruded a length of fillament into a scale placed on the bed. From there I can directly measure the extruder force. I combined this test with the new dual drive extruder from Creality and was able to dial in the spring tension to triple the force over the default extruder. That seems to have cleaned up my under extrusion for now. I do think the extruder is only half the issue, the hot end also is poorly designed and tends to clog up.

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