Good day,
I require help on deciding a sensor for my project. I have an auger powder filling machine, which fills exact to the weight. I would like to place a sensor in the main hopper of the machine, to detect when there is no more powder left. Since the hopper is full metal, I cannot use something like two lasers on each side of the hopper.
Of course the sensor will need to withstand being in different kinds of powder, and cleaned thoroughly
Anyone have any ideas? Much appreciated
Regards
The same way you're determining fill. Weigh it.
Only mostly empty or all empty? As in nothing left at all to dispense.
Thank you, that is a great idea! Are there any particular load cells you would recommend me considering they will constantly be in contact with different kinds of powders?
Thanks Tom!
I will be dispensing powders such as turmeric powder, chilli powder, black pepper powder, white pepper powder, flour
1/4 full is when I'd like to receive the right signal
Whatever is being used to weigh the dispensed material.
Since you're weighing, you can have a continuous readout either as weight directly, or as a %age, or even as count of remaining fills. You could also go green/amber/red as an idiot light.
Weigh the container! The load cell doesn't need to exposed to the material.
The hopper is attached via nuts to the top of the machine , so there is no gravity at play here. Would the load cells still work? Being attached directly to the hopper
The powders you mentioned will all have a VMD (Volume Measured Density) and that number will be less than one. You can determine the VMD of any powder using a simple formula. With a known VMD and knowing the volume of the hopper you weigh the hopper and you know the empty weight which becomes the tare weight.
Something else to consider is if the powder level in the hopper drops at a fairly uniform rate you can consider an ultrasonic sensor measuring from the hopper top to the powder level.
Back to VMD
CC setting (take a known volume of powder)
Weight of the sample (weigh the small sample)
VMD (volume in cc’s for 1 grain)
So what you have is:
CC Volume / Weight of Sample = Volume Metered Density
You can manipulate the numbers to fit your needs. I used grains because I have worked with grains in the past. So grains was my unit of weight.
Example:
If a powder has a VMD of .1064 , and the desired charge weight is 4 grains,
4 x .1064 = .4256, or . 43 cc’s.
Personally rather than find a way to weigh the hopper I would start with a simple inexpensive Ultrasonic Sensor for distance. Not sure how well a return pulse will bounce off the powders but these sensors are inexpensive and worth a try before a weighing system.
Ron
Ultrasonic doesn’t get a clean return from powder. Powder absorbs sound rather than reflect it.
Put the load cell under the hopper and use the empty weight as the tare
I wondered about that. Never tried it so wasn't aware if it would work with powder or not. Next, less seeing how the feed hopper is configured it may take some doing to weigh it during the process. Anyway then yes I would try running with the weight process. Only time I used ultrasonic was with liquid, actually water level in an ultrasonic cleaning process. Thanks for pointing out the issue with powders.
Thanks
Ron
Comes up all the time. Common project is to signal when sawdust collector gets full. Harder to weigh because of uneven density.
What are the hopper dimensions? Post photos of the outsides of the hopper.
When at 1/4 capacity, what do the surfaces of the various powders look like? That is, are they all relatively flat & horizontal, or does the powder hang up on the sides, so the surface is concave, with a big divot in the center, or what? Post photos of some examples (pasting in snapshots works).
If the OP has any of those experiences with the power, they need to have a vibrator on the hopper. Then the surface would be more level.
detect powder level in hopper at DuckDuckGo
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Powder Hopper Level Sensors | Products & Suppliers | Engineering360 (globalspec.com)
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