Practical Powder Measurement System for Analog Scales - No Zero Drift!

[J Willey]

Hi All,

I’m hoping to get some feedback on a product that I’m thinking about selling but don’t yet have the means to produce it with reasonable effort. So thanks for taking a look, and thanks a lot for commenting if you can. Is it practical? Would you be interested? Any suggestions?

I developed this over the past few years after finally giving up on (reasonably priced) electronic scales. My day job is in a laboratory where our rule for zero drift is a maximum of %1 of expected measurement range over 24 hours. So I know a little bit about measurement in general. Some of the scales I tried at home had more than 10% drift in under a minute. I do suppose there are decent scales out there ($$$$$), but I will contend that if you have to zero before every load (like automatic units), and even between every batch, you really don’t know how much powder you're dropping.

The problem is that old fashioned analog scales are practically unusable. They are clumsy on the benchtop. Easily knocked around. Virtually impossible to read consistently due to parallax error, not to mention the horrible ergonomics of trying to line your eye up on it while it’s in a usable location. They are extremely sensitive to even the slightest draft in your work space, even the draft caused by slowly moving your arm close by. And they do suffer zero shift as dust accumulates, although this is much more on the order of <1% in 24 hours.

So I think I solved all that. For my large batches and pistol rounds I love my RCBS Uniflow. But for my precision work this seems to be pretty ok.

Thoughts?

J Willey

 

[Baron23]

Perhaps a bit of explanation wrt to that control box, how you are measuring your bulk drop, the phone size display unit, what powders your trickler works with and how to accommodate different powders....etc.

Oh, and for some reason I can't get your pics to expand....click on them and they time out and don't load. Maybe a site issue....no idea.

 

[Edsel]

Oh, and for some reason I can't get your pics to expand....click on them and they time out and don't load. Maybe a site issue....no idea.

They load, give them time - they’re upwards of 12MB in size, that’s why.

Or, right - click and open in new window / new tab.

 

[Edsel]

I vaguely remember somebody else having done something similar - a beam scale with an optical trigger, many years back.

This was pre - 3D printing.

 

[Baron23]

Or, right - click and open in new window / new tab.

That worked...thanks. I'll keep that in mind for the future. Cheers

Oh, and now they are loading up instantly just clicking on them....WTF knows. lol

 

[Baron23]

Perhaps a bit of explanation wrt to that control box, how you are measuring your bulk drop, the phone size display unit, what powders your trickler works with and how to accommodate different powders....etc.

Oh, and for some reason I can't get your pics to expand....click on them and they time out and don't load. Maybe a site issue....no idea.

Now I can see the pics, I understand the display unit is a camera display for the scale index marks. Cheers

 

[ThePretzel]

I vaguely remember somebody else having done something similar - a beam scale with an optical trigger, many years back.

This was pre - 3D printing.

That is how the Prometheus works.

It uses a very nicely made brass balance scale with two optical beam sensors, dispensing powder into a funnel hung on the end of the balance arm with a little stopper-ball that keeps the powder in the funnel for weighing. You level the scale so that it properly reads zero when you have nothing inside the hopper besides the stopper-ball.

The first beam sensor triggers when the tail of the balance arm has lifted up to just below the point of being level, to slow down the trickler when you’re close to the target weight. The second beam sensor triggers when the balance has reached the point at which it is level, indicating that your target weight of powder has been dispensed. It’s a very simple and clever system running on an Arduino Uno, with only those 2 optical beam sensors needed to maintain great precision.

It shines a light behind the “comb” at the tail before reflecting it off a mirror to project the shadows of the balance’s current reading on an opaque panel at the front of the unit. The majority of the charge is dispensed by a top-mounted RCBS powder throw directly into the funnel, with a disk trickler (the same style as an Ingenuity Precision trickler, though the Prometheus came well before that) dropping individual kernels into the funnel.

The handiest part is that the stopper-ball has a wire leading up to the handle of the RCBS thrower, meaning it the stopper moves up and down as you operate the throw lever. Lift the lever and it lifts the stopper-ball, dropping your measured charge out through a funnel at the bottom. Then as you move the throw lever back down to drop the newly metered charge into the funnel, the stopper-ball drops back into place so the funnel can catch it without any powder spilling straight through. Thus as a user it fundamentally feels the same as using any traditional volumetric powder throw because you just move the lever up and down to dispense one charge into a case via a funnel on the bottom of the unit, then simply wait until the projection of the scale reading reaches the target weight (and the trickler stops moving) before doing it again.

 

[Edsel]

That is how the Prometheus works.

It uses a very nicely made brass balance scale with two optical beam sensors, dispensing powder into a funnel hung on the end of the balance arm with a little stopper-ball that keeps the powder in the funnel for weighing. You level the scale so that it properly reads zero when you have nothing inside the hopper besides the stopper-ball.

The first beam sensor triggers when the tail of the balance arm has lifted up to just below the point of being level, to slow down the trickler when you’re close to the target weight. The second beam sensor triggers when the balance has reached the point at which it is level, indicating that your target weight of powder has been dispensed. It’s a very simple and clever system running on an Arduino Uno, with only those 2 optical beam sensors needed to maintain great precision.

It shines a light behind the “comb” at the tail before reflecting it off a mirror to project the shadows of the balance’s current reading on an opaque panel at the front of the unit. The majority of the charge is dispensed by a top-mounted RCBS powder throw directly into the funnel, with a disk trickler (the same style as an Ingenuity Precision trickler, though the Prometheus came well before that) dropping individual kernels into the funnel.

The handiest part is that the stopper-ball has a wire leading up to the handle of the RCBS thrower, meaning it the stopper moves up and down as you operate the throw lever. Lift the lever and it lifts the stopper-ball, dropping your measured charge out through a funnel at the bottom. Then as you move the throw lever back down to drop the newly metered charge into the funnel, the stopper-ball drops back into place so the funnel can catch it without any powder spilling straight through. Thus as a user it fundamentally feels the same as using any traditional volumetric powder throw because you just move the lever up and down to dispense one charge into a case via a funnel on the bottom of the unit, then simply wait until the projection of the scale reading reaches the target weight (and the trickler stops moving) before doing it again.

I’m familiar with the Prometheus - the one in my memory is a regular beam scale with an optical trigger.

Let me try to find a video on it.

This was from many years ago…

 

[J Willey]

Perhaps a bit of explanation wrt to that control box, how you are measuring your bulk drop, the phone size display unit, what powders your trickler works with and how to accommodate different powders....etc.

Oh, and for some reason I can't get your pics to expand....click on them and they time out and don't load. Maybe a site issue....no idea.

Hi and thanks for asking. This system is manual, meaning that the user is loading the charge up to the value set on the sale. The control box has 3 variable channels preset to whatever speed you want to be high, medium and low. Nothing too fancy as far as that goes.

 

[J Willey]

That is how the Prometheus works.

It uses a very nicely made brass balance scale with two optical beam sensors, dispensing powder into a funnel hung on the end of the balance arm with a little stopper-ball that keeps the powder in the funnel for weighing. You level the scale so that it properly reads zero when you have nothing inside the hopper besides the stopper-ball.

The first beam sensor triggers when the tail of the balance arm has lifted up to just below the point of being level, to slow down the trickler when you’re close to the target weight. The second beam sensor triggers when the balance has reached the point at which it is level, indicating that your target weight of powder has been dispensed. It’s a very simple and clever system running on an Arduino Uno, with only those 2 optical beam sensors needed to maintain great precision.

It shines a light behind the “comb” at the tail before reflecting it off a mirror to project the shadows of the balance’s current reading on an opaque panel at the front of the unit. The majority of the charge is dispensed by a top-mounted RCBS powder throw directly into the funnel, with a disk trickler (the same style as an Ingenuity Precision trickler, though the Prometheus came well before that) dropping individual kernels into the funnel.

The handiest part is that the stopper-ball has a wire leading up to the handle of the RCBS thrower, meaning it the stopper moves up and down as you operate the throw lever. Lift the lever and it lifts the stopper-ball, dropping your measured charge out through a funnel at the bottom. Then as you move the throw lever back down to drop the newly metered charge into the funnel, the stopper-ball drops back into place so the funnel can catch it without any powder spilling straight through. Thus as a user it fundamentally feels the same as using any traditional volumetric powder throw because you just move the lever up and down to dispense one charge into a case via a funnel on the bottom of the unit, then simply wait until the projection of the scale reading reaches the target weight (and the trickler stops moving) before doing it again.

Hi ThePretzel. Thanks for responding here. I just had to google search the Prometheus unit and I'm pretty blow away. Just, wow. There is an auto-load function of my system coming in the future for sure but I've decided to go with the AI solution. I haven't jumped down that rabbit hole yet, but my research shows that there are some open source video capture algorithms out there that I can try. That's going to be gen 3 I think. Going now to watch some Prometheus videos. Thanks!