Scale For weighing a 20 Kg Gas Bottle using a load Cell Need help please with circuit Diagram

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Hi

I am tired of running out of gas in the middle of cooking. I would like to build a very basic scale to give me an indication of the gas I have left in the cylinder.

I was looking at my component suppliers website and came across a 50 Kg load cell.

I have attached the datasheet which basically tells me nothing.

The price of the load cell is favorable providing I dont have to buy to many more expensive pieces of equipment.

I want to connect it to my GSM telemetry equipment which has a 4-20 mA or 0 - 10 Volt input.

I can then add behavior statements that will send me notifications of the gas left and a warning when the gas gets low.

I am asking for a circuit diagram or some direction to making this basic scale.

Many thanks in Advance.
 

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Reloadron

Joined Jan 15, 2015
5,646
The Data Sheet tells me:
CAPACITY 50Kg
SENSITIVITY 1.0mV/V
EXCITATION 10VDC

So with a maximum Excitation of 10 VDC with a Capacity load of 50 Kg the output will be 10 mV. and if I multiply that X 100 my Full Scale out would be 1.0 Volts. Multiply times 1000 and full scale voltage out is 10 volts, so 0 to F/S = 0 to 10 Volts. When using load cells it is important, very important to have a stable reference (Excitation). A Google of 10 Volt Reference will likely bring up a dozen hits on suitable regulators. A lesser Excitation voltage will yield a lesser full scale out voltage. You would run the voltage out into an INA (Instrumentation Amplifier) and then into a chip like a uC. The uC analog input gets scaled into engineering units Kilo Grams or whatever. That or as I see you have a solution for a 0 to 10 Volt input.

Truth be known I can buy a simple;e and inexpensive bathroom scale likely for less than the cost and effort of building a scale circuit. Walmart or Amazon I see suitable scales for well below $20 USD.

Ron
 
Last edited:

ericgibbs

Joined Jan 29, 2010
10,768
hi Rodney,
The AD623 Instrumentation amp would amplify the output of that load cell to 0v thru 5Vout , using a 9V or 12V supply.
As it is a half bridge you would need a couple of close tolerance resistors#

Eric
 

GopherT

Joined Nov 23, 2012
8,012
Hi

I am tired of running out of gas in the middle of cooking. I would like to build a very basic scale to give me an indication of the gas I have left in the cylinder.

I was looking at my component suppliers website and came across a 50 Kg load cell.

I have attached the datasheet which basically tells me nothing.

The price of the load cell is favorable providing I dont have to buy to many more expensive pieces of equipment.

I want to connect it to my GSM telemetry equipment which has a 4-20 mA or 0 - 10 Volt input.

I can then add behavior statements that will send me notifications of the gas left and a warning when the gas gets low.

I am asking for a circuit diagram or some direction to making this basic scale.

Many thanks in Advance.

I thought about this project but concluded it is a lot easier and cheaper to just have an extra tank of propane in inventory.
 

joeyd999

Joined Jun 6, 2011
4,429
When using load cells it is important, very important to have a stable reference (Excitation).
No it isn't -- if you use the excitation voltage as the reference.

You would run the voltage out into an INA (Instrumentation Amplifier) and then into a chip like a uC.
This was how it was done 20 years ago. If he's going to use a CPU, there are many chips that will convert the low-level load cell output directly without the (analog) pain of an iamp. For instance, ADS1242.

With that said, I agree: a second tank is my preference. And, a bathroom scale from Home Depot will be cheaper, faster, and just as good for the application.
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Hi Everyone and thank you for all the advice etc.

There is no satisfaction buying a scale. For me this is my hobby and I also come from a country where we dont have access to walking in and buying a scale.

The thrill and satisfaction in building this scale and connecting it so it notify's me is exactly what I hoped to do.

Every time I build something from scratch I learn something new.

So I will take the advice and Google the circuits and "Try" to build my scale no doubt with lots of help from this forum.
 

ericgibbs

Joined Jan 29, 2010
10,768
hi R,
This circuit will give 0v thru 5V for 50kG.
The AD623 is all the components within the dashed rectangle.

R16 and R17 are the two resistors required to complete the full bridge.
1K at 0.01%

E
 

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Thread Starter

RodneyB

Joined Apr 28, 2012
697
hi R,
This circuit will give 0v thru 5V for 50kG.
The AD623 is all the components within the dashed rectangle.

R16 and R17 are the two resistors required to complete the full bridge.
1K at 0.01%

E
Hi Eric

Thank you so much. I will let you know how it goes.

Best wishes

Rodney
 

wayneh

Joined Sep 9, 2010
16,399
What would that do except for letting him know the propane temperature?
The commercial gauges show a temperature-corrected scale. It falls out of the "green" area only when there is no liquid left and you're literally running on vapors. It's better than nothing but obviously not as useful as a genuine level. A fish-scale is a good cheap solution. Just hang the tank from a spring scale.

There are also bluetooth load cells, so you can read the tank level from your phone.
 

Reloadron

Joined Jan 15, 2015
5,646
The commercial gauges show a temperature-corrected scale. It falls out of the "green" area only when there is no liquid left and you're literally running on vapors. It's better than nothing but obviously not as useful as a genuine level. A fish-scale is a good cheap solution. Just hang the tank from a spring scale.

There are also bluetooth load cells, so you can read the tank level from your phone.
That's about it with a pressure gauge, even a temperature corrected gauge. It's like it drops out of green about the same time your fire is gone. While I don't cook with gas (other than in the house) if I did I would always have a spare bottle at the ready. There is nothing worse that starting to cook and poof, out of gas. I liked Gopher's suggestion of always having a spare bottle. :)

Ron
 

MrSoftware

Joined Oct 29, 2013
1,907
I've seen temperature strips on the side of tanks. While in use, the liquid will be a different temperature than the vapor section, and you can get a general idea of the liquid level in the tank. I haven't used this myself and don't know how well it works.
 

mcgyvr

Joined Oct 15, 2009
5,394
We purchased a large floor scale to measure the weight of a nitrogen dewar so we could tell when it was getting low to pick up another...
Then came to find out that the consumption rate was too low for the scale to even see the change in weight for some reason I haven't dug deep enough to find out..
After 2 weeks the tank was 150+ lbs less in weight but the scale still showed the full weight of the dewar..
We needed to roll it off the scale and put it back on.. Which isn't an "easy" task for a single person to achieve..

Luckily the nitrogen supplier went to a new gauge on the tanks that actually work reliably this time..
 

djsfantasi

Joined Apr 11, 2010
6,799
I've seen temperature strips on the side of tanks. While in use, the liquid will be a different temperature than the vapor section, and you can get a general idea of the liquid level in the tank. I haven't used this myself and don't know how well it works.
I've used them ubiquitously. They're available in the US, at Walmart for example, for $10 for a package of two. See!
 
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