Readable Gauges

Discussion in 'The Projects Forum' started by jpanhalt, May 12, 2015.

  1. jpanhalt

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    Jan 18, 2008
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    Recently, I sort of completed a project to read remotely the inclination of an implement on a tractor. I am currently working on a different approach to determine the inclination, but I am also looking for options for the human interface.

    I used a GLCD in the above prototype. It worked, but was difficult to read in all lighting conditions. I need to indicate a "null" or level condition, and assume there are modern electromechanical indicators that do that.

    Can anyone point me to a source? Google turned up a lot of stuff related to homebuilt aircraft, but no generic answers. What I am thinking of is something like an analog CDI or HSI (to use airplane terminology) that I can output my inclination data to.

    Thanks, John
     
  2. strantor

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    Wondering why you don't just go with an analog meter movement since you want analog style readout of an analog value.

    Maybe its because you're dealing with a micro that doesn't have analog output capability? If that's the case, maybe you could convince your micro to speak canbus just well enough to move a needle of a canbus gauge. Those examples aren't cheap but a speedometer or pretty much any gauge harvested from the junkyard from an '08 or newer car will be canbus.

    Or just use a hobby servo and be done with it
     
  3. jpanhalt

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    Analog meters are not out of the question. Converting digital to them can be done with PWM and DAC . My original thought was something like an old fashioned galvanometer.

    I was hoping some modern device with a servo driven the needle would avoid the bounce one sees with such analog meters. I don't want to build the meter, nor do I want to hack a meter from an automobile cluster. I am assuming off-the-shelf items are available and just don't know where to start my search.

    John

    Edit: It seems the type of indicator I am looking for may be called a "steam gauge," which is used in contrast to "glass cockpit."
     
    Last edited: May 12, 2015
  4. mcgyvr

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    jpanhalt likes this.
  5. jpanhalt

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    I think I found some place to start: http://www.cypress.com/?rid=2638 Good discussion of stepper motor gauges. Those trim gauges are basically the type of indicator I am looking for, but a bit more generic.

    Now to find the actual gauge that is relatively blank.

    John
     
  6. strantor

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  7. strantor

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    It is strange to me that nobody seems to sell servo analog gauges. That seems like something sparkfun would sell a ton of. Maybe a niche to be filled there. Does not seem like it should very hard at all to take an analog meter, yank the coil out of it, and replace it with a hobby servo.
     
  8. jpanhalt

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    Thanks for the link. After a little sleep, I think finding the mechanical/stepper part of the gauge will be relatively easy. Maybe something like this:
    upload_2015-5-12_21-38-58.png

    And the electronic part also appears to be pretty much plug'n play (see the links in the Cypress link in my post). The hard part may be finding the right gauge case and faceplate that can be modified for my needs. I am pretty sure that in Cleveland there must be a few shops to do the face printing. If not, I came across some DIY methods for doing the same.

    As is so often the case today, the hardest part is coming up with the proper search terms.

    John
     
  9. strantor

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    For sure you've popped open an analog meter movement? You don't need anything silk-screened or custom made! You can take any old meter, remove one screw and pop the legend plate out, put it in a flatbed scanner. Scan it and you get the dimensions. Use anything more versatile than MSPaint and just draw your own scale over the old one and print! I print them on adhesive backed label paper, and stick it right to the old legend plate. Then trim around the edges with a box cutter. In your mind's eye you're probably picturing something obviously amateur looking, but it's not, I promise. Especially if the meter case has beveled edges. I swear it looks just as professional as the original. I've sold these things to industry clients and I wouldn't have, if there was even a whiff of "less than perfect."

    If it were my project I'd take a panel meter like this, open it up and affix the needle to a servo like this, print a new label for it, and throw it all back together. I don't see why it should need to be any more complicated than that. Your micro can send an instant value directly to it with PWM, no need for keeping track of needle position always (even through power loss), converting value error to generate needed steps movement, building stepper drive circuitry, any other positioning nonsense. And for under $20!
     
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