Stepper motor to build a mineral dispenser. A primer.

Discussion in 'The Projects Forum' started by HBB, Apr 5, 2016.

  1. HBB

    Thread Starter New Member

    Mar 3, 2012
    25
    1
    Hello,

    I am using a manual mineral dispenser system to add Urea and Mineral salts complements in a mill. We prepare our own food for cattle.
    We use it weekly, the mill is a tractor driven 60 HP that grinds corn grain plus dry hay in two separate chambers. A mixer is located below the chambers.
    We add the mineral complement and the urea by hand at the mixer stage.
    We dose by volume.
    Then the mix goes to an elevator that outputs the final product into the feeder where the cattle eats.

    We want to automate this process building two dispensers capable to drive two grilon disks that will be interchangeable. The grilon disks will have about 8 holes each. Perhaps 10, but the idea is still the same. We will build two dispensers, one will be regulated for salt and the other for urea.
    So the motor will have to turn the disks 45 degrees to change to the next dose.
    The size of the holes will let us change the volume dispensed, as well as the time used to turn a 45 degree step.

    I have a modest experience in electronics, I am able to use my old Tectronix 2215 scope and do an acceptable PCB with ExpressPcb.

    This will be my first stepper motor project, but if I succeed, it will be a big step forward for my small ranch.

    I am looking for this advice:

    If you think that a stepper motor solution is suitable or not,
    A primer information project to get inspired

    Thanks very much,
    Kind regards
    Horacio

    Two complements:
    I have already read the stepper motor section of your books. Very clear!
    I am a civil engineer and still fly my Cessna C140 for fun.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
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    You have to determine the torque required to turn the disks, most likely you can introduce some gearing as I assume you do not need rapid operation?
    Max.
     
  3. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    Whatever you do you will want to impliment feedback, either disk position as an absolute or more simply just the location of tbe hole that just emptied.

    With feedback your stepper idea will work but it sounds like a complex solution to a relativly simple problem. Although I may be missing something and mean no offence.

    If you use holes as small as your ingreediance will readily flow into and out-of and then simply count the holes as they drop their loads you can easily vairy the dose.

    A standard small PLC and some sort of motor gearbox and a couple of inductive proxcimity switches is all you need.
    The code would simply drive for 'some' holes and stop when the requisit number had emptied, leaving the last open hole in the discharhe position.
    You would also be well advised to time betwen consecutive ho,es whilst running and raise an alarm if the disk is slow or stopped.
    Two sensors could be used to ensue that they agred with each other within, some small margin, or a sensor fail alarm would be raised.

    Your PLC and potentally a small HMI could even hold recipies, prompting operators for manual dosing and primary ingreediance whilst handling the addatives for you.

    You could even add load cells to weigh the batch and calculate the correct dose, but that is a little more complex and potentially expensive.

    I do this stuff for a living, all be it with hydro turbines not mixers, if you want speciffics, kit recommendations or even somone to write you some code or design the control panel just let me know.
    You are wlcome to advice if I am arround but I think forum rules prevent me from offering any paid help.
    That said it realy isnt hard and if you go with a PLC I know and have software for I would be hapy to get you up to speed so you shouldnt need to pay anyone...

    Regards,
    Al
     
    Last edited: Apr 5, 2016
  4. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,128
    266
    Stepper motors are overkill here, and often fraught with subtle and sometimes nasty problems for the newcomer.

    Sounds like a job for a PLC, geared DC motor and a few sensors, this would be a pragmatic and cost-effective solution
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    Posting the volume and weight of a "dose" would improve the suggestions for dispenser design.
     
  6. HBB

    Thread Starter New Member

    Mar 3, 2012
    25
    1
    Hello,

    Thanks for all the answers.
    The figures for actual production are:

    1. Production: 25 Kg per minute

    2. Dispenser 1
    We use controlled liberation urea in granulated form, and we add this volumes
    40 cubic centimeters that weigh 35 grams
    The dispenser should push 10 doses of this size per minute

    3. Dispenser 2
    We use a pelletized mineral for cattle, and we add this volumes
    75 cubic centimeters that weigh 50 grams
    The dispenser should push 10 doses of this size per minute

    I did an automatic feeder for my dog and I used a windshield motor, geared, taken from an old Peugeot 505, 12 volt.
    It runs nice. I could use a stronger one, for instance from a light truck, with its gearbox.

    If anobody can point me to a PLC reading to start, pls ?
    I never worked with PLC electronics, but seems to be this is the time!

    Thanks again,
    Kind regards,
    Horacio
     
  7. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    PLC... Look at schneider Modicon. The M221 range software is free, for single unit implimentations and has a simulator built into the IDE so 7ou could start learning programming tomorow.
    Kit is solid, well appointed and reasonably priced...

    Wiper motor, now your on track. Internall it just uses a switch which stops it at some point of its rotation, unless its shorted out externally, the start signal. remove the signal and it always stops in the same place.

    I am not sure you would want to use one in an industrial environment wher anything importent is going on but the methodology, with a little extra monitoring is probably what you want to build.

    By the way, why a disk? Think plug valve with a cup as opposed to a fully drilled port.
    esy to manufacture, easy to make different sized dose plugs, easy to drive...

    have a look at Parvalux motor geear boxes... Many types sizes thay will do a few tens of RPM's with huge torque aand low power consumption at 24VDC. you would probably be best with 90 degree worm as opposed to a planetrry unit, if only because they are easier to mount.
    I use them to control spear valves on 100kW turbines driving a needle on 30mm thread into a valve at up to 20 Bar head.

    Happy to give you speciffics / sketches if that will help.
    if you go Schneider I could send a basic project to get you started if you can wait a few days but I would recomend you get a leg up and then have go yoursely it will be mire satisfying and give you the ability to maintain and modify.
    Once you have been shown some basic concepts its relativly easy.

    Can you read a panel wiring diagram? if so you cam program in ladder logic once you get a short primer in addressing and number storage in binary based kit.

    Regards
    Al
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    For what it's worth, you might consider a small augur type delivery system.

    Such a system isn't prone to jamming, can be infinitely adjustable for dosage, and is easy to power with a DC gear motor. Put the augur in a horizontal position in a tube below the hopper and let gravity feed the augur. Pass each grain batch under the augur, and turn the motor on/off as required for each batch.
     
    Evanguy likes this.
  9. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    I Agree, an auga would work well, provided you still measure the rotation and thus displacement of the medium but it is much harder to build and with low dencity material can compress it affecting rate monitoring.
    A partilly empyt inclined augar would fix this buts that is hardly a practical proposal.

    To be fair, given the material, I think a small auga would work well but you would have to validate it at various hopper levels and feed rates.
    There are many ways to go, you could even go linear and drive the thing with pnumatics getting a single dose per stroke.

    The primary reason for suggesting a plug valve type construction was its simplicity and robustness. You could make one with a lathe and a drill press.

    I hope you find a solution that works for you, give me a shout if you need speciffics.
    Al
     
  10. HBB

    Thread Starter New Member

    Mar 3, 2012
    25
    1
    Thanks for all the answers
    I will see in Buenos Aires for PLC prices and specs.

    Kind regards,
    Horacio
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    If you don't have that much I/O look at a PLC based Smart Relay, much cheaper than many PLC's, Many are basically identical and relabled.
    Max.
     
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