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Kitchen weight sensor

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Grossel

Well-Known Member
Hi.

I have a kitchen weight where only the display is broken. So I have decided to find out how to make use of the sensor itself.

The censor have four wires conected to it, different colors. So I guess that it might work same way as hall censors, but doesn't know.

Plan is to use a breadboard and a circuit that can turn on a LED when the weight goes over a certain value. I can always adjust with a potmeter, so any curves isn't neccesary. Just to prove it works.

Question is: How to determine what is input and what is output wires from this weight censor?
The weight is not pilled apart so I haven't measured any resistance between wires yet.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi.

I have a kitchen weight where only the display is broken. So I have decided to find out how to make use of the sensor itself.

The censor have four wires conected to it, different colors. So I guess that it might work same way as hall censors, but doesn't know.

Plan is to use a breadboard and a circuit that can turn on a LED when the weight goes over a certain value. I can always adjust with a potmeter, so any curves isn't neccesary. Just to prove it works.

Question is: How to determine what is input and what is output wires from this weight censor?
The weight is not pilled apart so I haven't measured any resistance between wires yet.
hi,
Look at this pdf, to be sure, we need more information regarding the cell.:)
 

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Grossel

Well-Known Member
hi,
Look at this pdf, to be sure, we need more information regarding the cell.:)
Thanks, I'll try this.

btw: It might take more than two weeks before I get time to check this out. Exept for some resistance values, I suppose the principle is the same.
 

tytower

Banned
Oatley Electronics sell an experimental load cell kit pretty cheap Oatley Electronics

I bought one and followed the pdf and it works great.
It has a chip on the side of a drilled out aluminium bar.Runs on 2.5V.everything included bar the top & bottom plates.

I recommend it .Fun There should be one available in Europe
 
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Grossel

Well-Known Member
I've read the pdf and the censor is a load cell type shear beam. I still can't provide more info yet, but I will.
 

Grossel

Well-Known Member
Here's a picture of the sencor.

As you can se there is four wires, Black, red, white and green.
 

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tytower

Banned

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Grossel

Well-Known Member
Did you look at the reference in my post? Its exactly the same ! $18
Make it easy for you 5KG ELECTRONIC SCALE KIT
Now I found it. Your link put my browser to the main page of that webside.

But the provided pdf file only contains mechanical infos for assembling procedure. It doesn't answer my questions. That is: No electrical info about the load cell as censor is provided, and that's what I need.
 
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arunb

Member
you need the appropriate load cell amplifier for your load cell. Most load cells are wheatstone types. Since the signal levels are low, they need to be amplified.

You might buy a suitable ampilfier but I suspect they may be costly...you could also make an amplifier using op amps or use a dedicated load cell interface IC such as CS 5516/5520, but then you may also need a microcontroller to interface to the IC.

Try googling CS 5520 or CS5516

thanks
aa
 

Grossel

Well-Known Member
You might buy a suitable ampilfier but I suspect they may be costly...you could also make an amplifier using op amps or use a dedicated load cell interface IC such as CS 5516/5520, but then you may also need a microcontroller to interface to the IC.
I plan to use opamps for this aplication :)
I guess I'll assemble an instrumental amplifier.

When I get time, I'll test the load cell assuming color codes in the table is valid for it.
 

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tytower

Banned
On the one I have built from an $18 kit there are 4 wires only and no shield at all. The four wires feed to a board with an LED display . I would assume red and black are the normal power and ground lines and the voltages checked seem to verify this , so you only have to interpret the voltages on the other two
 

Vikky

New Member
hi,

Recently i have build a force sensor using the laod cell. Here i am displaying output in Newton. The 100 grm weight show 0.9 N. Even i can detect a change in 20 grm.

For this i have used INA326 instrumentation amplfier from TI. If it is available near you try to use it since the load cell output voltage change is very very less (in terms of uV), and you require a highly stable amplifier to detect the signal.
 

Grossel

Well-Known Member
Solved

Hi. This weekend I managed to measure the voltages on the load cell while it's still connected to the circuitry (not pilled apart yet).

I can confirm that the color on the wires is correct.

However I measured the voltage difference (green/white wire) and it's very low voltage variation. Even one kilogram makes a voltage difference of only 0.4 mV.

This case is solved. Thank you.
 
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