gotleyb
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Sensing the level/volume of a tank full with woodchips

Sat Feb 23, 2019 5:49 am

Hello, I've searched the internet for a sensor that can measure the level of a tank full with woodchips. So far I only came access with liquid level sensors and I wondered if there is something similar for solides (maybe a volume sensor?).
I was thinking about using the ultrasonic sensor hc-sr04. But I'm afraid it won't work properly because this is a small metallic tank so there can be interferences with the ultrasonic signal, and the woodchips surface is very rough and can absorb the sound instead of reflect it. Does anyone have some experience with similar projects? Thanks

klricks
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Re: Sensing the level/volume of a tank full with woodchips

Sat Feb 23, 2019 3:48 pm

gotleyb wrote:
Sat Feb 23, 2019 5:49 am
Hello, I've searched the internet for a sensor that can measure the level of a tank full with woodchips. So far I only came access with liquid level sensors and I wondered if there is something similar for solides (maybe a volume sensor?).
I was thinking about using the ultrasonic sensor hc-sr04. But I'm afraid it won't work properly because this is a small metallic tank so there can be interferences with the ultrasonic signal, and the woodchips surface is very rough and can absorb the sound instead of reflect it. Does anyone have some experience with similar projects? Thanks
I would suggest a light beam and sensor of some sort. Laser or IR. Google.......
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Idahowalker
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Re: Sensing the level/volume of a tank full with woodchips

Sat Feb 23, 2019 4:46 pm

A TFMini
Without knowing why you are deleting my postings, I will not know how...

drgeoff
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Re: Sensing the level/volume of a tank full with woodchips

Sat Feb 23, 2019 6:14 pm

Do you want a variable measure of how full the tank is or a bilevel signal that the fullness is below/above a fixed predefined level?

tpyo kingg
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Re: Sensing the level/volume of a tank full with woodchips

Sat Feb 23, 2019 8:17 pm

Would these sensors handle wood chips?

https://tutorials-raspberrypi.com/infra ... y0a02yk0f/

MarkR
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Re: Sensing the level/volume of a tank full with woodchips

Mon Feb 25, 2019 12:00 pm

The laser time-of-flight sensors would be ok with woodchips, I imagine. They work well in the dark (not so well outside in sunshine).

One problem might be dust and crud building up on the sensor. The time-of-flight sensors can cope with a piece of glass in front of the sensor, it would need cleaning periodically I suppose. Moisture might also be a problem in any case, you probably want a moisture resistant enclosure.

Ultrasonics might work too, but you can't put a glass in front of that, so I think dust would probably get in pretty quickly and be uncleanable from the cans.

EDIT: Maybe car parking sensors (which are generally ultrasonics) would be more resilient than the maker type ones with the exposed cans

gotleyb
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Re: Sensing the level/volume of a tank full with woodchips

Mon Feb 25, 2019 12:30 pm

Thank you very much for the answers.
I prefer to have a continuous measurement but I can compromise with an above/below some fixed point.
From the answers it seems there is no escape from checking different types of sensors :D ;) .

I also thought of something else, to put a small camera inside the tank and draw a line. With some kind of simple image processing to detect the line and its length.

again thank you very much for the suggestions, now time to work.
Any other inputs will be highly appreciated.

MarkR
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Re: Sensing the level/volume of a tank full with woodchips

Mon Feb 25, 2019 12:36 pm

It may be a major mechanical change, but, place the whole tank on a load-cell, and measure the weight?

My guess (I haven't worked with woodchip systems myself) is that it will be a messy, dusty, possibly damp environment which will destroy many types of sensors easily. So while lots of things might work for a short time, the real trick may be to find something which will continue to work after months or years deployed.

So for cameras or optical sensor - lenses are going to get covered in crud, for ultrasonics, the sensors will get filled up with muck.

I don't think the simple optical reflecting sensors will be useful, I suspect woodchips have a wide range of albedo (e.g. how dry they are, what kind) so it won't be very accurate.

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Imperf3kt
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Re: Sensing the level/volume of a tank full with woodchips

Mon Feb 25, 2019 12:44 pm

Though not as technical, a literal cut in the side of your tank, will reveal how full it is.
The cut should be wide enough to see through, but not enough to weaken the structure or allow chip to escape en mass.
Maybe you could monitor such a thing with a camera?

Laser sensors are useful, but are fixed in position.
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IanS
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Re: Sensing the level/volume of a tank full with woodchips

Tue Feb 26, 2019 10:44 am

A cut could seriously weaken the tank. How about a high-contrast not-wood-or-tank-colour strip stuck to one inside wall and a camera mounted on the opposite lip. Then see how much of the strip you can see.
Just don't put the camera where it might get damaged getting the chips in or out.

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Imperf3kt
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Re: Sensing the level/volume of a tank full with woodchips

Tue Feb 26, 2019 9:16 pm

IanS wrote:
Tue Feb 26, 2019 10:44 am
A cut could seriously weaken the tank.
You would think so, but it depends on the tank's construction.
I mentioned it because I actually work in a sawmill and this is the method we use on two 1000cubic foot tanks for wood chip.
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omegaman477
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Re: Sensing the level/volume of a tank full with woodchips

Fri Mar 01, 2019 11:15 pm

gotleyb wrote:
Sat Feb 23, 2019 5:49 am
Hello, I've searched the internet for a sensor that can measure the level of a tank full with woodchips. So far I only came access with liquid level sensors and I wondered if there is something similar for solides (maybe a volume sensor?).
I was thinking about using the ultrasonic sensor hc-sr04. But I'm afraid it won't work properly because this is a small metallic tank so there can be interferences with the ultrasonic signal, and the woodchips surface is very rough and can absorb the sound instead of reflect it. Does anyone have some experience with similar projects? Thanks
If the tank is closed top, a industrial resonance sensor would work. They calculate the void above the chips by determining the resonant frequency. Used a lot for Grain Silos.
..the only thing worse than a stupid question is a question not asked.

blimpyway
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Re: Sensing the level/volume of a tank full with woodchips

Tue Mar 05, 2019 10:14 pm

Give the ultrasonic sensor a try...

Depending on how big the tank is, you can make a thin styrofoam square slightly smaller than the tank internal dimensions.

It would just sit on top of the chips. As the chips drain out the plate will drop down and offer a good reflective surface for the ultrasonic range sensor.

But if the tank is small then plain ultrasonic should work.

Since the sensor is faced down dust should not accumulate too soon.

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Imperf3kt
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Re: Sensing the level/volume of a tank full with woodchips

Wed Mar 06, 2019 3:42 am

blimpyway wrote:
Tue Mar 05, 2019 10:14 pm
Give the ultrasonic sensor a try...

Depending on how big the tank is, you can make a thin styrofoam square slightly smaller than the tank internal dimensions.

It would just sit on top of the chips. As the chips drain out the plate will drop down and offer a good reflective surface for the ultrasonic range sensor.

But if the tank is small then plain ultrasonic should work.

Since the sensor is faced down dust should not accumulate too soon.
Using that method, you can only ever empty the tank and not fill it.
Perhaps some form on LIDAR would work better, such as a laser distance finder?
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