Low Cost Weighing Scale

I am trying to design a low cost weighing scale for 1- 100Kg range with precision of 0.5Kg
Can someone provide pointers for good and cost effective load cells.
I shall be using MSP430 as the controller and other circuitry is somewhat finalized.
Load cells ( cost effective ) remains unknown area to me.
Will appreciate if someone can provide useful pointers.

Thanks and regards.

Will this be tension or compression? Meaning will the weight sit on the scale (compression) or hang from the scale (tension)?

There are dozens of load cells out there that will work. I have used Omega Load Cells as well as many others. There are what I call "Pancake" designs in a variety of ranges and also sizes, you don't mention a size or configuration?

Ron

Cost of the load cell: 98% of the cost of the entire project.
Cost of the rest: 2% of the cost of the project

MikeMl said:

Cost of the load cell: 98% of the cost of the entire project.
Cost of the rest: 2% of the cost of the project

Click to expand...

I believe that covers it well. The majority of the quality load cells I worked with were about $1,000 and up.

Ron

Can you build a balance type of scale?

For low cost, think ordinary spring, linear position sensor (slide potentiometer, rotary encoder, or etc, etc), and Hooke's Law.

You could save quite a bit of money by using a strain gauge rather than a complete load cell:
https://www.omega.com/pptst/SGK_Linear_gages.html
Attach the strain gauge to a steel beam that flexes under the load of the item being weighed. I think an accuracy of 1/2 kg should be possible.

Thanks for replies.

Reloadron: Intend to design compression type weigh scale.
BobW; Will work on Strain Gauges to start with the project.

If you want to start with some strain gauges I would suggest Micro-Measurments now a division of Vishay. Nothing wrong with Omega as Bob linked to but when you start working with strain gauges there is quite a bit to learn, including the mounting process and all of the adhesives used for different measurement environments. Converting the u strain to usable units and building up your bridge, really some interesting stuff. You will essentially be building your load cell.

As to buying a load cell, that is another option and as mentioned, they can get pricey. A good pancake load cell for compression was about $700 to $1,000 USD give or take, Omega sells a good line there is also Futek and others. Nice part is with a good quality load cell all the work is done for you. Provide the excitation voltage and signal condition the output and you are done.

Ron