We have already seen till now how we have constructed our project in PCB .
Liquid filler at this point needs calibration.
In this article we will discuss the calibration method.
The first step is to dimension correctly the RG resistor.
From the weight sensors article we already know that :
a) For a 1Kg load cell we are going to need Gain=1,07421875/0,005473=196 for a 1.1V arduino reference analogReference(INTERNAL); So we need a Rg=312 Ohm.
b) For a 20Kg load cell we need a Gain = 3925 for a 1.1V arduino reference analogReference(INTERNAL);
So we need a Rg=15 Ohm.
In the last two articles we have worked on the breadboard.
We have seen that the circuit worked well so we need to construct it in PCB and then calibrate it.
We will start with the KiCad schematic file and then we will see the PCB layout.
Then we will construct a weight board with the load cell installed on it.
Once done with this step then we should be able to calibrate the device.
The calibration will be discussed in a next article.
In the first part of liquid filler we have made the user interface.
LCD buttons and circular menu were made.
Now it is time to add the relay and the weight sensor.
We will keep working on our breadboard.
In this article we will see how to connect the relay then our load cell amplified by the INA125 and lastly the modified code from the last time.
A sensor is usually an analog device. Analog devices are connected at the analog ports of arduino.
Arduino with the use of AnalogRead function can read the analog sensor value from the specified analog pin.
The Arduino board contains a 6 channel 10-bit analog to digital converter. A 10 bit analog to digital converter as we have seen in the "Binary Decimal and Hexadecimal numeral systems" equals to a 210 – 1 = 102410 (0-1023 => 1024 steps).
If the resolution of arduino (1024 steps) does not cover your project you should use an external ADC converter with more that 10 bits.
For example you can connect the LTC2400 ADC which happens to be a 24 bit analog to digital converter.