Home Built Load Cell Based Scale with digital display

Discussion in 'Tow Vehicles, Hitch & Towing' started by popup-flyer, Nov 23, 2021.

  1. popup-flyer

    popup-flyer Active Member

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    After seeing Anthony Hitchins thread on using a load cell and volt meter I was inspired to build a unit that utilizes an Arduino micro controller and load cell amplifier do decode the returned information and display it in the units you want to see.

    An attempt at humor, the box you see the LCD display sticking through that contains the boards is the one that the load cell came in :D

    This is just V 1.0, hastily wired, used wood as a stand and parts shoved in that box for proof of concept.

    To build one you would need an HX 711 amplifier (this is 5 but same price as 1 from spark fun)
    https://www.amazon.com/gp/product/B07MTYT95R/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

    LCD Display:
    https://www.amazon.com/SunFounder-Serial-Module-Display-Arduino/dp/B019K5X53O/ref=sr_1_2_sspa

    an Arduino UNO or leonardo
    https://www.amazon.com/Arduino-A000066-ARDUINO-UNO-R3/dp/B008GRTSV6/ref=sr_1_3
    or
    https://www.amazon.com/Arduino-org-A000057-Arduino-Leonardo-Headers/dp/B008A36R2Y/ref=sr_1_3

    Finally a load cell, this is the one I used which can go up to 2 tons:
    https://www.amazon.com/gp/product/B077YHFCX4/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

    I linked to the proper Arduino controllers but there are knockoffs. I have both, used the knockoffs on this making it a few dollars cheaper so total cost is about $84 before tax when using the "coupon" etc... and not including the wood, wire or steel I had laying around.

    I used a known weight to calibrate it once and it is pretty accurate +/- 1 lb or so which is close enough for trailer weights.

    If there is interest I can write up an https://www.instructables.com/ document.

    Photos of me weighing the tongue on my HW276. I was able to determine how much a full water heater, propane bottles and battery affect my tongue weight last night:

    20211122_165021.jpg
    20211122_165026.jpg

    One thing I will say on this is that "position matters" when placing weight on the load cell. Weight needs to be relatively well centered. What you are fundamentally measuring is the force applied to the metal in the load cell or its "flex". if you go far to one side or the other the weight can change by as much as 20 lbs.

    Because of that I am considering making a 4 load cell version that is combined and displays the combined weight for V 2.0 but it would cost a lot more. I found a 5 ton "pallet scale" on amazon for $500 so the closer the price gets to that... :D
     
    Last edited: Nov 23, 2021
  2. Anthony Hitchings

    Anthony Hitchings Well-Known Member

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    last time that I used my system (Octobner this year) I just put the (same as yours) load cell between the platten on my floor jack and the underside of the axle (axle is below spring) and for placement that works as well as anything it seems - even though it may look "mickey mouse" .

    I do not have a photo of this current setup, becasue my current axle has no perches on its lower surface (my old axle did). And all of my photos were taken for the old axle setup.
     
  3. Anthony Hitchings

    Anthony Hitchings Well-Known Member

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    I have used my system for the tongue, and I find that its easier to use my bathroom scale for the tonge weight.
     
  4. popup-flyer

    popup-flyer Active Member

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    That photo was just below the max weight for the bathroom scale. That was without 1 of the 2 propane tanks. I did that to verify weight accuracy as compared to the bathroom scale. The tongue weight is actually a bit more.

    The wife/kids keep asking what I want for Christmas so I think I will just say another load cell. I can plug them both in to the same controller and already have 4 more signal amps. This way I get weight for both wheels at the same time for single weight value display:D

    I plan to build a second wood "stand" until I get that so I can put both wheels on at the same time for even weighing.
     
    Last edited: Nov 23, 2021
  5. generok

    generok Well-Known Member Gold Supporting Member

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    I appreciate the build and the time you spent. Beyond my patience though.

    Nicely done!
     
  6. WrkrBee

    WrkrBee Un-Supported Member

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    Or you could get a digital bathroom scale and use a beam to keep the load within the scale rating.
     
  7. popup-flyer

    popup-flyer Active Member

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    Yeah I have done that, I didnt really build this to weigh the tongue, but the axle weights. and vehicle axle weights when loaded etc...
     
    Last edited: Nov 24, 2021

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