Measuring force with Arduino and Matlab

I have a calibration problem with the following code. This code accesses an Arduino. The Arduino is in turn connected to a force sensor via an amplifier. The aim of the Matlab code is that when a known weight is placed on the force sensor, for example 3kg, the value is displayed in Matlab as 30 Newtons via the Arduino.

Matlab displays values between -1030 and -1020 as the zero point for the measurement. With Arduino, the values on the serial monitor for the zero point fluctuate between 267-269.

The aim is to set Matlab to zero and to display 30 newtons in Matlab when, for example, 3 kg is applied.

The following voltages were determined via Manuware when different weights were applied to the force sensor:

kg Volt

1 0,06

3 0,18

4 0,23

5 0,3

6 0,39

7 0,44

8 0,46

9 0,52

10 0,6

Answer 1

[Sahas]

Hi @Diana Gaier,

As per my understanding, the Arduino code gets the voltage readings from a force sensor. The MATLAB code uses the voltage readings and converts them into force measurements, in Newtons, using a conversion factor and plots the values in the end.

I went through the MATLAB and Arduino code snippets provided; I suggest doing the following changes in the codes:

In the Arduino code, separate the conversion and reading steps while reading the sensor values. Please use the following syntax for the “analogRead” function:

void loop() {

int sensorValue = analogRead(analogInPin);

int sensorValue2 = analogRead(analogInPin2);

float voltage1 = sensorValue * (5.0 / 1023.0);

float voltage2 = sensorValue2 * (5.0 / 1023.0);

Serial.print(voltage1);

Serial.print(" ");

Serial.println(voltage2);

delay(1000);

}

In the MATLAB code, the “readVoltage” is using the incorrect conversions from analog to voltage. Instead, use “readVoltage” function in the following manner:

% Read voltage from Arduino
x0_voltage = readVoltage(a, 'A1');
z0_voltage = readVoltage(a, 'A5');

From the calibration data provided, the relation between voltage and force seems to be linear and the conversion factor comes out to be 30/0.18 = 166.67.

% Define conversion factor based on calibration data
conversionFactor = 30 / 0.18;

Now multiply the voltage reading by the conversion factor to get the force in Newtons.

% Convert voltage to force in Newtons
x0_force = x0_voltage * conversionFactor;
z0_force = z0_voltage * conversionFactor;

Incorporate these changes into your code and make any necessary adjustments to the plotting if required.

I hope this is beneficial!

[Diana Gaier]

Thank you!

I did these changes, but now somehow i have a new error running the code:

Unrecognized field name "VidObj".

Error in aufnahme>aufnahme_OpeningFcn (line 157)

stoppreview(handles.VidObj);

Error in gui_mainfcn (line 215)

feval(gui_State.gui_OpeningFcn, gui_hFigure, [], guidata(gui_hFigure), varargin{:});

Error in aufnahme (line 42)

gui_mainfcn(gui_State, varargin{:});