Homemade powder trickler Help and suggestions plz

Discussion in 'The Projects Forum' started by Jacob J, Dec 9, 2009.

  1. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Hello

    Look at this piece of equipment:

    http://www.chuckhawks.com/rcbs_chargemaster1500.htm

    It is an expensive piece of reloading equipment and I dont have the money to buy one. Here in Denmark such a "machine" costs around 700 dollars and I thought I might build one myself.

    I have a digital scale, that can weigh in grains, which is the units we reloaders use for measurering the amount of powder we want in a cartridge.

    My idea is:

    Take my digital scale, take a powder trickler like this:

    http://images.cabelas.com/is/image/cabelas/s7_210605_imageset_01?$main-Large$

    Connect it to a little DC motor to it, and then somehow make an circuit that controls when the motor should stop.

    But how can I make such a circuit, that I can connect/hack to my digital scale and stop the DC motor, when the scale reaches a surtain weight?

    The Scale I have is one like this:

    http://www.dealextreme.com/details.dx/sku.15762

    Any ideas?

    Hope you can help me.

    Best regards

    Jacob
     
  2. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Hmm the signal that is displayed on the digital scales display, can I copy/dublicate that signal, so that it sends the signal to the display, but also sends the signal to my circuitboard? Then the circuit I should build would be programmed via an input keyboard with a seperate display.
     
  3. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Here is a little drawing of the unit I would like to build and hook up to the DC motor and the digital scale.

    I forgot that I need one more button, I forgot the start button, so there needs to be 5 buttons.
     
    Last edited: Dec 9, 2009
  4. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    The way I see it, the process will be like this:

    I push each digits button, to get the display on my unit to show the weight I want it to throw. Then I push the start button wich starts the DC motor. The digital scale sends a signal to its display and to the unit, the unit compares the incomming signal from the scale with the one ive pushed in on the units display and when it gets close it slows down the motor and when the scale and the programmed weight is the same, the DC motor stops.

    Sounds easy, but I am not very good at electronics. Ive build a PWM controller for a DC motor, but thats also it.

    But is this hard to build?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Interesting project... I have also considered doing something similar, as I am also a reloader. :)

    I don't currently have an electronic scale though; I have been using an ancient Ohaus model 505 magnetically damped manual scale. I use an ancient Lyman powder throw that dispenses by volume. It's reasonably accurate, except when dispensing very small charges, or when using rather long extruded powders.

    I made my own powder trickler using 1-1/2" PVC pipe made for plumbing, coating the inside with graphite powder to decrease the likelihood of static electricity causing problems.

    I used a piece of 1/4" O.D. stainless steel tubing with a small hole drilled in the middle for the trickler tube, and a matching 1/4" hole at a slight angle through the PVC. The lower end of the home-made trickler is a plugged 1-1/2" to 1/2" reducer fitting, and it is mounted to a standard octagonal electrical box that I had sitting around. I used a small knob designed to control a potentiometer or switch. It works quite well, and I probably spent less than $3 on the parts to build it with.

    It has a distinct advantage over the commercially available models, as I can make the powder reservoir as large as I wish, and I can place an ordinary PVC cap on it to keep it closed up to avoid contamination or spillage in case I am careless enough to knock it over. I would not recommend such a design for use with black powder, however it is perfectly safe for smokeless powders. Black powder is particularly sensitive to shock and static electricity; they are to be avoided at all costs.

    Back to the direct problem at hand:
    I do not currently have one of these scales, although they are quite reasonably priced.

    It may or may not be possible to connect the scale to an external circuit; at the moment it's an unknown. Such devices designed for mass production often have custom ICs designed to reduce the component count to a bare minimum.

    The automatic turn-off at 1 minute intervals is a problem.

    But if these obstacles can be overcome, I would approach it using a microcontroller that would read the scale output, control a stepper motor to rotate the powder trickler, and report the results to a program running on a PC, or otherwise display/report the results.

    The microcontroller program would have to be "smart" enough to slow the step rate of the motor as the charge neared the correct value. It would also need to have the capability to warn the user if the resulting charge was exceeded by more than 1/10 grain, or other lesser limit as appropriate for the caliber and powder being loaded.

    Ball powder could be a problem, as there may be considerable delay between the balls dropping into the hollow shaft of the trickler and exiting the shaft/tube.

    Flake powders such as Bullseye and 700-x may tend to "clump" together, particularly during humid weather.

    Cylindrical powders may also exhibit tendencies to clump together, but not as bad as flake-type powders.

    Anyway, I'm sort of rambling here, but just writing down ideas and concerns out that need to be addressed.

    I picture this happening in several stages:
    1) A starting charge of perhaps 90% of the desired load is placed on the scale.
    2) The trickler starts dispensing powder while the uC (microcontroller) both controls the step rate and monitors the scale.
    3) As the scale output nears the desired weight, the uC slows the step rate of the motor.
    4) When the uC "sees" that the scale is reporting just under the desired weight, the motor is stopped.
    5) If at any time the uC detects that the desired weight is exceeded by 1/10 grain, or other limit set by the user, an unsafe load indication is given.

    An unsafe load can be either over or under weight. A simple scale has no way to determine if a load will be safe for a given cartridge.
     
  6. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Very nice idea with the safety function. Maybe a little speaker could give out a "piiiip".

    I also ment it to have a slow down function and maybe a variable DC speed to compensate for different powder types as I think if it goes slower it will do it more accurate.

    I have no experiance with microcontrollers and how they work or how I would put this project together. I need a person who can tell me wich parts I need and can help me putting it together.

    The idea with the computer is good, but then you would have to make a program and that I think, is a to big challenge for me atm.

    How does the signal look comming from an LCD display? How many wires for each digit and so on?
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Oh, and by the way - if anyone is concerned about safety issues with reloading cartridges, it's me. ;)

    I have been reloading for quite a few years. It is a very safe hobby, if you simply follow the proper procedures.

    If you have ever left a candle burning unattended, you have exposed yourself to much greater danger than a responsible reloader would.
     
  8. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    yes I know, as long as you keep to the reloading data, it cant go wrong.

    Can you tell me how I get further with this project?

    What would you do?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    I was thinking more of LEDs for indications of progress. Something like a yellow LED lit for under weight, a green LED lit for correct weight, and a red LED for over-weight.

    You are basically correct with the slower speed being more accurate. However, as I mentioned in my long and rambling reply above, different powders will have different dispensing characteristics simply due to their dimensions. I only covered three basic powder shapes for nitro-based powders.

    I understand. Keep in mind that this kind of thing will be more of a long-term project rather than something that can be "thrown together" overnight. There are (most certainly!) safety issues involved.
    If you do not have very good soldering skills, that will be something that you can work on in the meantime. Purchase and assemble several electronic kits to improve your skills.

    The computer is not an absolute necessity. However, that is one way to "talk" to the uC. Without an interface to a computer to tell the uC what to do, you will need an input device (such as a keypad) and a display (such as an LCD) so that you can enter commands and know they are understood.

    This is a problem that does not have an answer now. At the moment, I do not have one of these scales. :(

    It will require spending money to obtain one or more of the scales, and then opening it up and probing for signals. It could be a long and complex process.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    It's not quite that simple. Any change in seating depth, primers, powder or powder weight, powder lot, bullet type - and you need to start over at 85%-90%, and work up from there.

    I'm trying. This is not an interactive board. Sometimes it can take days for a reply.

    Be very slow and cautious about this type of project.

    This is not something that can simply be thrown together without lots of thought.

    I have been thinking about this very same type of project for several years, and have not built it yet.
     
  11. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Well I am the type of person who want to buy all the one day and build all together the same day.

    The scale ive linked to is cheap and its free shipping world wide, so I could easily buy one more and open it and maybe hack it myself, but the problem is, how I get the signal to be compared with the put in digits on my unit, so it stops when needed.

    As my drawing shows, I would like 5 buttons, 3 to change the digits (10, 1 and 0,1) and a reset and a start button.

    I would still need to do some sort of programming the microcontroller right? I cant just send in a signal from a push of the button and then it changes the digit on the display?

    What if I hacked the signal from the scale and put it into a controller, then I would have the signal from the digits ive put in on the display on the unit and both signals would be send into another controller and when both signals match it stops the motor. Dont know if controllers work that way, but it is an idea, but okay, then you couldnt make the thing with the motor slowing down when getting near to the right weight.

    Is the schematics hard to make for such a unit? Wich components would be needed for those functions mentioned:

    Input weight to display on the unit
    5 buttons, start, reset and digit adjustment
    Slow down motor speed when getting near the right weight
    Displaying yellow (not enough powder), green and red light(to much powder)
    Make a sound if there is to much powder
    Potentiometer adjustment of motor speed (powder type compensator)

    I am sure a lot of reloaders would be very interested in such a project and if I/we could make some schematics wich would be "easy" and cheap to build, then it would be great. And all the new functions wich we already have embedded to such a system would be nice to have.
     
  12. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Don't typical electronic scales have a significant lag time in settling on the real/final value? My Ohaus 0.01 g scale does (Scout model) does. My guess is that your setting would have to have a built-in lead (i.e., stop at a value just before the desired value), then let it settle, and error out, if the settled value was not within the limits you wanted.

    I am all for reloading. ;)

    John
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    This does not bode well for a reloader. Your enthusiasm is appreciated and acknowledged, but things involving propellants require, by their very nature, a great deal of caution.

    That's just one of the problems.

    So simple, right? In actual practice, it may not be so simple.

    Yes.
    No, sorry. That's wishful thinking.

    That's sort of the idea. Except for the other controller. But slowing down as the correct weight is approached is most appropriate.

    It's not hard to make a schematic. However, making a correct and proper schematic can be a vexing exercise.

    This is a must.
    Random numbers at best at the moment. Interesting concept, though.
    Absolute necessity.
    Indications of weight and progress are definite necessities.
    Make a sound if there is to much powder[/QUOTE]
    Not necessary; if overweight, the green LED would be off and the red LED on. Complications of the design are not necessary and particularly undesirable from a reliability standpoint.
    No, this will have to be built into the program of the uC, and will have to be a "learned behavior" type of thing.

    I'm sure they would be interested.

    I guess I'd better get started, eh? ;)
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    I didn't know you were a reloader. :) You are my friend, John. There are few of us around nowadays.
     
  15. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Well the thing with the speed adjustment isnt hard to make I think.

    Look at my drawing.

    The first output to the motor is the fast/the start speed. You may want to be able to define the speed on that if you have powder thats hard to work with.

    The second outpud to the motor is the slow one, that kicks in when it gets close to the right weight. It would be very nice to control the speed the motor is having when it needs to weigh the last 1/10 gn onto the scale.

    It may be nice with this to be done with a PWM controller, but it is a lot simpler with the to pots and atm I am not so consurned about the power usage of the unit.

    Well SgtWookie, if it isnt to much trouble for you and it isnt hard to make the schematics, then it would be very appreciated if you could come with a little sketch of how the wires would be connected.
     
  16. BMorse

    Senior Member

    Sep 26, 2009
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    how about using a small dc gear motor, (stepper is not necessary, since you don't really care how many steps it takes) and attach an auger type of feeder system to it, this way it would also break down the "clumps" in some powders and it would dispense it evenly....

    [​IMG]

    This company sells small augers for automated powder fillers >> http://www.augermfgspec.com/

    and as for the scale, it is going to be hard to "tap" into the electronics of it, since as sarge stated they are usually made to be cheap, so the main uc for it is probably a black blob on a PCB.....

    Bets way to "tap" into the scale would be to tie directly to the strain gauges and use a uc to determine the weight.....

    My .02
     
  17. gerty

    AAC Fanatic!

    Aug 30, 2007
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    I'm still using my 30 year old RCBS scale, model 5-0-5 I think. After setting the powder thrower on my Dillon, it's not needed again until I change caliber.
    You're right Wookie, there's not as many reloaders as ther used to be.
     
  18. SgtWookie

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    Jul 17, 2007
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    You appear to be considering using a brushed-type DC motor. Even though these can be available in closed units, the commutator rotating against the brushes still emits sparks as connections are made/broken.

    As you already know, any possible sources of ignition must be kept away from the reloading work area. This makes a brushed DC motor unsuitable for use in a project that is designed to meter propellant, which is by its' very nature highly flammable.

    While a resistor can be used to slow a brushed-type DC motor, there is a very substantial loss of torque; the greater the resistor used, the more the torque is reduced. It is extremely difficult to maintain control of a brushed DC motor at low speeds using resistors; the motor will almost always run too fast, or stall completely.

    Stepper motors do not cause such sparks to occur, as they do not have brushes nor commutators. They have two or four field windings, depending upon construction, and many common types of steppers have a fixed magnet in the rotor. Stepper motors also have a very high amount of torque at low speeds, and their speed can be very closely controlled, which makes them an excellent candidate for this type of project.

    Control of a stepper motor via a uC is really quite easy, particularly if the motor is of a unipolar type.

    There are usually five or six wires coming from a unipolar stepper motor. One or two of the wires are the +V supply. The remaining four wires are the "ends" of the four windings. By sinking current from one winding at a time in a certain order, the motor can be made to rotate, or "step" in precise increments.

    A uC connected to a power driver IC such as a ULN2003/ULN2803 Darlington array makes such connections very easy.

    The motor speed/step rate can be controlled very precisely by the uC.

    However, the big problem here is how to get an indication from the scale that the desired weight is approaching?

    I don't have one of these scales.

    Even if I did have one, and could get it apart without destroying it, it would take some time to analyze the signals.
     
  19. SgtWookie

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    Jul 17, 2007
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    I've explained to our OP why I feel that brushed DC motors are not suitable for this. Reloading is a safe hobby, as long as one follows the rules. One of the primary rules is that any source of ignition must be kept away from the reloading area. In my opinion, this precludes the use of brushed DC motors.

    The high stall torque, precise control, and absence of sparks provided by stepper motors makes them very attractive candidates for this project.

    An interesting idea. Propellants used in reloading need to be metered in very small and precise amounts. In larger calibers, such as .30-06, one might use up to 57 grains of powder; and the powder may be rather large and cylindrical, such as IMR-4350. Towards the smaller end of the scale, like for .380 Auto, the charge may be around 2.4 grains of Bullseye powder, which is a very small and fast burning flake-type powder, and the tolerance needs to be held very closely. Bullseye flakes are so small that it would be difficult to measure them. By comparison, the IMR-4350 looks like small telephone poles.

    If one were to use an auger-type trickler, the auger size might need to be changed for various powders being used. It is an interesting idea, and worth pursuing.

    I'm afraid that by going that route, the accuracy of the scale would be destroyed. It undoubtedly has a built-in self-calibration routine that is executed whenever it is powered up. In order to get the same accuracy of the scale (which is quite impressive, by the way) in a uC, the entire routine in the embedded electronics would have to be duiplicated in the uC.

    And we're back to the issue of safety, which involves the reliability of the unit. While these scales seem to be quite accurate, I don't know how long they stay accurate - and if they become inaccurate, do they report the failure?

    If errors are made in the design and construction of a project such as this, there could be very serious consequences, including destruction of a firearm using the reloads, and injuries to the person operating the firearm.

    This is not something that can simply be thrown together overnight.
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    That's the same one I have. Ohaus was purchased by RCBS many years ago; they simply re-branded the Ohaus to RCBS, and kept the Ohaus model number. It's a very good manual powder scale. It beats the heck out of my old Redding scale, which did not have magnetic damping. It took forever for it to settle down.
    [/QUOTE]After setting the powder thrower on my Dillon, it's not needed again until I change caliber.[/QUOTE]
    Which model? 550? 650? All of my stuff is ancient. I have an ancient Pacific press; it was made prior to WWII. A dear old friend left it to me when he passed many years ago.
    No, there aren't. It's a sad thing. Urban sprawl has wiped out many shooting ranges in the States. The Government was very supportive of civilian marksmanship programs right up until the early 1970's.

    My Dad got me started in the NRA Junior Marksmanship course when I was 5. It was a great program, and very enjoyable. When done properly, target shooting is one of the safest and most enjoyable sports one can participate in.
     
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