Making weighing machine

[ismbn]

Hello There...

I am Planing to make A weight machine...
I have not Worked on analog before, this why i need Lots of support, as you guys are the only my Teachers now a day...

Please Help me to Select the load cell for weight upto 200Kg, which 1 i can use, i seen some of the load cell but thy are very costly.

What things I need to study Please Guide me.

when i broken a weighting machine... There is 4 load cells are connected. when google i got this.
https://www.alibaba.com/product-detail/50kg-Micro-Load-Cell-for-Body_1965146440.html

this load cell is cheep, but how can i connect to get the capacity till 150 or 200...

Thanks for Your Time

 

[esp1]

hi,
A 4 load cell weigh scale will require a strong metal frame and a Base plate, the 4 cells are mounted near the corners of the Base plate.

If you used 4 off, 50Kg load cells you could get a maximum load of 200Kg, the load cells would be connected in parallel, you may require a 'summing pcb' for adjusting the individual load cell outputs.

The output of the load cells would require amplifying, using a instrumentation amplifier.


E

 

[ismbn]

Thanks for the Reply,
so please tell me How to connect these 4 sensor in parallel?

 

[esp1]

hi,

If the load cell has 4 wires, one for +V and one for -V excitation, the other two wires are +V signal and -V signal.

If you do not use a balancing PCB, connect all 4 of the +Vex to together, then all of the -Vex together.
The same applies to the +Vsig, connect all together and the the -Vsig togther,

So you now have 4 wires.

The +Vex is connected to +5V or +10V and the -Vex to 0V.

The +Vsig and -Vsig are connected to an Instrumentation amplifier, I use a AD623 as it will work from a single supply voltage.

Using a balancing PCB is a little more complicated, its used where the 4 cells do not have the same unloaded voltage offset.

E