Force Sensor
Force sensors are physical devices that measure the amount of force applied to them. They come in a variety of shapes, sizes, and sensitivities, and are typically constructed as a variable resistor. When not pressed, the resistance is very high, usually over two Mega ohms. As pressure is applied, the resistance decreases.
Accuracy
It is important to note that these sensors are not very accurate for absolute force or pressure measurements. This is because pressure is a function of force divided by area, and the contact area changes depending on where and how the sensor is pressed. Therefore, these sensors are best suited for qualitative measurements with Arduino projects, such as determining how hard someone is pressing on something. If an accurate weight measurement is required, a different type of sensor should be used.
Connecting to Arduino
To connect a force sensitive resistor to an Arduino, the circuit must be built in a simulator such as Tinkercad Circuits. This is a free online Arduino simulator with a separate tutorial video available in the description of this video.
Code
Once the circuit is built, the code must be written to read the values from the force sensor. This code will vary depending on the type of Arduino being used, but typically involves setting up an analog input pin and reading the value from the sensor. The code should also include logic to map the analog values to a range of values that make sense for the application. For example, if the sensor is being used to measure the amount of pressure applied to a button, the code should map the analog values to a range of 0 to 1, with 0 representing no pressure and 1 representing the maximum amount of pressure.
Measuring Resistance with Arduino
It is essential to understand that the Arduino is unable to measure changes in resistance directly. To measure the changing output from the force sensor, it is necessary to build a voltage divider using a second resistor in series with the sensor. A close inspection of the breadboard reveals that the two pins of the sensor are connected to 5 volts and the other pin is in series with a 10 kilo-ohm resistor, which is then connected to ground. The exact value of this resistor that works best is contingent on the resistance range of the sensor; however, a 10 kilo-ohm resistor is usually a good starting point. Adjustments can be made up or down from there.
Voltage Divider
The middle pin of the voltage divider, which is connected to both of the resistors, is connected to one of the Arduino’s analog input pins. The voltage on that pin will fluctuate as pressure is applied to the force sensor. This can be demonstrated in TinkerCad, which has a slider to simulate pressing on the sensor. A multimeter can be used to measure the voltage on that pin. When the sensor is not being pressed on, the reading is zero volts. As the force on the sensor increases, the voltage starts to rise and the LEDs start to light up. When the force is reduced, the voltage goes back down and the LEDs turn off.
Code
To measure the changes in voltage, code needs to be written for the Arduino. This code will read the voltage on the analog pin and then use that data to turn the LEDs on and off. The code will also need to include a delay to ensure that the LEDs do not flicker. The code should also include a function to map the voltage reading to a range of values that can be used to control the LEDs. This will ensure that the LEDs turn on and off at the desired voltage levels.
Testing
Once the code is written, it is important to test it to ensure that it is working properly. This can be done by pressing on the sensor and checking the voltage reading on the multimeter. The LEDs should turn on and off at the desired voltage levels. If the code is not working properly, it may need to be adjusted or rewritten.
Sensor Pin and Sensor Reading
At the top of the code, variables are declared for the sensor pin and the sensor reading. This is done to ensure that the Arduino can accurately read the sensor value from the pin and store it in the variable for later use. The sensor reading is then used to determine the output of the LED pins.
LED Pins
The LED pins are also declared as variables. This is done to ensure that the Arduino can accurately control the output of the LED pins. In the setup function, these LED pins are set as outputs and serial communication is initialized. This allows the Arduino to print the sensor reading out to the serial monitor.
Loop Function
In the loop function, the analog read command is used to read the sensor value from the sensor pin. This value is then used to control the output of the LED pins. The serial print command is also used to print the sensor reading out to the serial monitor. This is useful for calibrating the sensor and determining what to do with the sensor reading depending on the desired output. The analog read command converts the voltage on the multimeter to a number between 0 and 1023, allowing for more precise readings.
Understanding Force Sensors
Force sensors are devices that measure the amount of force applied to a surface. They are commonly used in robotics, automation, and other applications where precise force readings are required. Force sensors typically consist of a strain gauge, which is a device that changes its electrical resistance when a force is applied to it. This change in resistance is then used to measure the force applied.
Connecting a Force Sensor to an Arduino
In order to use a force sensor with an Arduino, it must first be connected to the Arduino’s analog input pins. To do this, a voltage divider must be created by connecting a separate resistor in series with the sensor. This will reduce the voltage from the sensor to a level that is safe for the Arduino’s analog pins. Once the voltage divider is in place, the sensor can be connected to an analog input pin on the Arduino.
Reading the Sensor Value
Once the sensor is connected to the Arduino, the sensor value can be read using the Arduino’s analogRead() command. This command will return a value between 0 and 1023, which is proportional to the amount of force applied to the sensor. This value can then be used to control LEDs, motors, or other devices.
Using the Sensor Value
Once the sensor value has been read, it can be used to control other devices. For example, the sensor value can be compared to different threshold values using if statements. If the sensor value is greater than a certain threshold, then a certain action can be taken. This could be turning on LEDs, controlling a motor, or printing out values to an LCD screen.
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Connecting the Sensor to the Arduino
The Arduino can be connected to the force sensor directly, as it is unable to measure changes in resistance. To read the sensor, analog read should be used in the code, and the pin value should be serial printed to calibrate it for the application.
Adjusting the Resistor Value
The resistor value can be changed to affect the output voltage, which in turn affects the range of readings when the sensor is pressed. This can be used to adjust the readings to the desired level.
Using a force sensor with an Arduino requires building a voltage divider using a second resistor in series with the sensor. The code needs to be written to read the voltage on the analog pin and turn the LEDs on and off. Testing should be done to ensure that the code is working properly and the LEDs turn on and off at the desired voltage levels. With the right setup, it is possible to use a force sensor with an Arduino.
Force sensors are easy to use with an Arduino. All that is required is to build a voltage divider by connecting a separate resistor in series with the sensor. Once the sensor is connected, the sensor value can be read using the Arduino’s analogRead() command. This value can then be used to control other devices, such as LEDs, motors, or LCD screens.
This tutorial has provided an overview of how to use a force sensor with an Arduino. By connecting the sensor directly to the Arduino, and adjusting the resistor value, the readings can be calibrated for the desired application. For more Arduino tutorials and cool science projects, please visit www.arduino.cc.
