active weigh ing of cable drum

Question

this ought to be easy but my brain doesn't seem to be working.......

problem.... a drum of wire or filament etc is mounted on a shaft (axle) supported at both ends........... what is the best way to continuously weigh and display its weight, in grams, as te contents are used?

weighing one end is simple but for an accurate reading both ends must be weighed at the same time for a single indication of weight.

solution could be electronics or arduino or raspberry pi

please help prevent me going nuts.....

michaelkellett · Answer

You don't give enough context to give a good answer - it would be good to know how big and heavy the drum is, what's the tension in the wire, how is it all controlled and a load more stuff (environment, accuracy required, budget etc.)

The very simplest way to do it is to hang the drum from a yoke attached to a single load cell - you can buy these easily enough but your talk of Arduino or RPi suggests you may not be in the classic load cell price range. If you are not too fussy you could buy cheap load cells from China.

If the drum is heavy and rotates fast or the wire tension is significant it might get harder, maybe use load cells to support each end of the drum and if necessary sample the weight (or more correctly down-force) multiple times per revolution.

MK

michaelkellett · Answer

Connecting 2 load sensors in series is not possible, connecting load cells in parallel is sometimes done but not a good idea.

The best way is to give each load cell its own amplifier and use multiple ADC inputs.

Here's an article on E14 that should give you some ideas:

3d printer filament roll holder and monitor for Arduino

MK

malcolm51 · Answer

sorry for lack of detail

load axle/ spindle rests on 2 supports, one each end, and a yoke is not practical

weight range 50g to 2kg

as an example this could be a roll of 3d print filament.

tension is zero.... weighed at rest point and/or continuous reading (varying with tension/ rest) displayed on 7seg display or (more likely) a TFT display attached to arduino or pi.

low budget... reasonable accuracy e.g +- 5g at rest zero tension.... environment closed acrylic case with steady temperature and airflow (no outside forces...

hope this helps......

can 2 load sensors be connected in series to give single reading of entire load (both ends added together)

unfortunately was in R&D but brain fried with excessive age (and little experience of arduino/ pi)...

malcolm

active weigh ing of cable drum

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