Beam balance upgrade... anyone tried this?

[LeadThrower]

The recent thread on digital scales got me thinking about an old idea that I've not yet implemented:

The idea is to power a powder trickler with a small motor (think cordless screwdriver) to dispense powder onto the pan of a beam balance. The power to the trickler will be cut by an optical switch which is tripped by the magnetic damping plate of the balance. It should be possible to throw "perfect" charges by placing the optical switch on a vertically adjustable mount on the back side of the balance. By perfect, I mean charges as consistent as the balance can manage.

I'm a tinkerer, so any comments of "why bother" can be answered with "because it's possible". It might not save time or improve the loading process in any way, but it's worth exploring imho.

The question is: Have any of you tried something like this? If so, how did it work?

[edsmith]

I havn't done one but it sounds like a great idea,looking forward to your progress.the one question I think is stupid is,why would you want to do that? answer is because I can, you moron.

[George_J]

I have not tried this either, but two things come to mind.

First, the powder dispensing should be intermittent, to avoid scale overshoot.

Second, if there was a small mirror on the top of the beam of the scale, and a laser pointer used as a light source, then the light detector could be above the scale. As the scale beam tilts, the mirror does too and changes the position of the reflected light beam. The further the detector is from the mirror, the greater the resolution of position of the scale beam.

Hope that made sense.

Here is a two pack of red laser modules for a whopping $4.62, shipping included.

http://www.dealextreme.com/details.dx/sku.10091

[Lead Fred]

My Redding powder measure drops the load so close, it may only take a turn or two to get it where it needs to be.

[mike in co]

its called a charge master...or a variity of names in the digital world......
the time lag on movement and hystorisis is an issue with beams scales.....


mike in co

[1hole]

One company made a sort of viberating electrical trickler some years back. It seems not to have done very well in the market but the idea is workable. I've been toying with doing one for myself but my old, shop made 3# trickler so well I just haven't felt much need.

[DLCTEX]

I use the Frankford Arsenal battery powered trickler. Inexpensive and would be easy to adapt.

[462]

I say, give it a try. Don't let others stand in the way of your ideas.

I wouldn't want one, but if you have the ability to make it, go for it.

[dromia]

There is one here:

http://targetmasteruk.com/

[LeadThrower]

Lots of good thoughts out there. Thanks! I'm looking at Fairchild Semi and DigiKey. photodiodes and phototransistors are less than a buck. A stepper-motor IC is around $10, and a stepper motor (new) is about $20. Trading leg-work for $$ and hitting the used electronics shops around town, I suppose I could make this thing for under $10. Computer printers have cheap unipolar stepper motors. I should be able to find one for free.

A double-sensor system should avoid hysteresis and similar overshooting problems. Stepper runs fast until first sensor is tripped and then runs in half-steps (or micro-steps) to finish the powder drop.

Thanks for the link, dromia. That's pretty close to what I was thinking, except my sensor will be permanently mounted to my scale. It's good to see someone getting very consistent drops with such a simple sensor arrangement.

[jimkim]

Here's one. http://www.larrywillis.com/accurate.html

[abunaitoo]

It's been done before.
I think AMT came out with it first.
Lyman bought the rights to it.
I'm not sure if they still make it.
I have the one made by Lyman.
Lyman Autoscale.
Here's a link.
http://www.gunaccessories.com/lyman/scales/index.asp

Works good with long stick powder.
Not so good with ball powder.
OK with flake powder.

I've found that if the trickler tube is angled up, it works better.
Also cannot have any wind blowing on it.