I’d like to set up a project where I have [n] load cells set up in parallel, and I write data out to the screen identifying each cell and what weight it is sensing. I’ve attached a screenshot of what I’ve already purchased to set up this project. What other materials do I need? Is it possible to use one output screen for [n] load cells? I’d like to start with 2, but eventually when this goes to production I will need 20-30 working in parallel and writing output to a remote server. Thank you for your help.
Yes, you can use load cells in parallel. However, 20-30 is unusual. You may find minor differences in the load response, especially with inexpensive, poor quality load cells. Depending on your desired weight resolution, this may have the effect of a given load showing as different weights based on which load cells contribute to the signal. This can sometimes be solved using trim resistors/pots but that’s a lot of cells to try to match.
Thank you for your replay brow, this helps a lot. Let’s not worry about the 20-30 for now, I’d like to just make the concept of a more than one working simultaneously for starters. Weight sensitivity/resolution is definitely going to be a factor, as most of what I’ll be measuring is < 0.5kg, and nothing over 1kg. Would you have an AC power supply recommendation, or should I find a 5V battery to get started?
If you’re looking for a AC power supply for the RedBoard/Arduino, the 9 volt power supply below will work nicely. There’s a voltage regulator on the board that brings the 9 volts down to the 5 and 3.3 volts the board needs.
Thanks. Another question, I realized, for my project, that I will probably need to use disc load cells and not straight bars, as the items I am weighing are going to be enclosed within a box (I am attempting to make a smart-fridge-like device). Do you have any disc recommendations for this, considering I only need up to about 1kg? Can you tell me why the disc cells tend to be much more expensive than the straight bars?
Once the cells are electrically parallel, you won’t be able to determine which one(s) are contributing to the load.
For example, take a typical four-cell freight scale platform for weighing pallets.
If it’s in good working condition, the load should read the same no matter where it is place on the surface.
However, if you wanted to determine how the load was balanced or a center of gravity (not uncommon in motorsports or aerospace), each cell must have it’s own amplifier and instrumentation.
What you’re calling disc cells are more commonly referred to as button cells.
You could put three or four button cells on a surface and then place a plate over the top of them to weigh stuff but that top plate will slide right off at the smallest side load.
However, a single shear beam cell can be made into a scale platform by simply bolting two parallel plates to either end.
Shear beams can also offer higher resolution since they deflect (bend) more for a given load.
Thank you for that detailed response. I’ll shelve the button cell concept for now then. What you said about the cells being electrically parallel makes sense; I assume if I wanted to read them as individual scales I’d have to have their output sent to an FPGA to be able to parse each cell individually? Would you have any FPGA recommendations to read in data from the 1kg straight bars?
