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Propane level monitoring with RD3 hall-effect sensor

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    #31
    Hey guys - I'm trying to accomplish this same thing. I'm trying to build a long life battery powered monitor with a trigboard (~1.5uA deep sleep power draw).

    I'm also wondering how you are driving the gauge to get the test readings in order to setup the voltage scale? I have a bunch of magnets laying around. I'm trying with one of these:

    https://a.co/8yyupGb

    I'm having a hard time reliably turning the dial with the magnet. It seems as though I have to put one end on the opposite side of the gauge's arrow? I'm also wondering if the mag field of these neo magnets is too strong and may affect the readings? Or is that something that shouldn't matter?

    I have what seems like a linear scale from 20-80%, but every time I put the gauge back at a whole number, I get a different reading from the sensor. The values are close, but definitely an error margin in there. Are you just swagging a number after a bunch of readings? Or are your numbers pretty solid? I'm driving a bare 49E with 3.3v. Wondering if the cheap sensor I got from amazon is good. I'll probably order some from digikey to be sure.

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      #32
      Originally posted by mzuniga View Post
      Hi guys and thanks Polarblair. I have made my own sensor using your very useful instructions. Now, I have a question as I'm getting some weird results. From 80% to 50% full tank I get very distinct, almost linear voltages. However starting on 40% the slope changes and I get almost the same voltage for each % change in tank capacity. Can you think of something that might be causing this? I'm using the suggested sensors and hardware. Thanks in advance for any insight. This is how my curve looks like now:

      Click image for larger version

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      What did you use to make your own sensor and how (what is it connected to) to read the output? Thanks in advance for sharing!

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        #33
        I saw strange behaviour too when the hall effect sensor wasn't oriented properly. I initially tested it by holding the sensor to the guage while sat infront of the PC to get live feedback and moved the sensor to a few positions, then rotate the gauge and let gravity move the needle. Check results, reposition and test again. I had the sensor flipped over the wrong way initially which gave wierd results.
        are you using the same sensor I did? Also same remote ready gauge?

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          #34
          Originally posted by Polarblair View Post
          I saw strange behaviour too when the hall effect sensor wasn't oriented properly. I initially tested it by holding the sensor to the guage while sat infront of the PC to get live feedback and moved the sensor to a few positions, then rotate the gauge and let gravity move the needle. Check results, reposition and test again. I had the sensor flipped over the wrong way initially which gave wierd results.
          are you using the same sensor I did? Also same remote ready gauge?
          Got some parts on order to try this. Should the rounded or flat side of the sensor be placed against the remote-ready gauge? What did you use on the PC to view the voltages?
          Awesome project! Thanks to everyone for contributing.

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