load cell
I would like to link 4 load cells sensors to an arduino. I am trying to follow this tutorial. I am using this load combinator
and I need to connect it to this load amplifier
The combinator has E+ E- A- A+ SLD outputs
The amplifier has E+ E- A- A+ B- B+
How do I connect the 2 boards?
According to Vishay Revere, they should be connected in parallel like this: -
It's likely that on each corner of the scales the cells are half-bridges not quarter bridges. The only 3-wire quarter bridges I've seen are for when trying to cancel long-wire volt drops.
You wire the four half-bridge load cells like this: -
But you have to take care you get the wiring polarity correct or you can end up with weight cancellation and no signal. You just have to experiment a little but that's the basic wiring.
For the first diagram you showed, each half-bridge is excited in parallel with the other half-bridges and two half bridges are paralleled for each input. It does the same as the above but is less sensitive (or put the other way has a larger full-load capacity).
As for amplifying the signal I'd use an instrumentation amp (inamp) like this: -
It's basically 3 op-amps connected as below: -
There are plenty of options and optimization or best choice of inamp relies on knowing the power supply you have available for your project.
Best Answer
Connect:
Amplifier
........ Combinator
E+ ... Red
E- .... Black
A- .... White
A+ ... Green
HX711 data sheet
___________________________
Because:
On this Sparkfun page you will find the diagram below. At upper right I've added a red rectangle to highlight the relationshp between the amplifier connector labels and the Sparkfun colour-based connection names.
Your Maitek HX711 amplifier is similar in functionality to the
Sparkfun HX711 amplifier EXCEPT that your version uses both amplifiers/ channels in the HX711 and sparkfun only use one.
HX711 surprisingly good data sheet and demo library and code - zip file - I have not opened it.
From Elecrow here
Lots of relevant information here and here
HX711 on Arduino forum
Here is one example of the HX711's use:
Note the two input channels - only one shown in use.
If a second bridge was used it could share the V_AVDD and ground leads (E+ / E- = excitation +/-)
From this better-detailed than many seller's page
GITHUB Arduino library - An Arduino library to interface the Avia Semiconductor HX711 24-Bit Analog-to-Digital Converter {ADC} for Weight Scales.
Instructaaaaaaaaaaables
50 assembled boards for $US0.70 each !!!!