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# Grove - Round Force Sensor FSR402

The Grove-Round Force Sensor(FSR402) is a force sensitive module. At the end of the sensor there is a round force sensitive resistor, the resistance of which depends on pressure applied to this resistor. Simply say, the greater the pressure, the smaller the resistance. However, the output of this sensor is not strictly linear, so we do not recommend it for accurate measurements. For more detail about the pressure-resistance diagram, please check the FSR402 Datasheet

As the you can see, this module is based on FSR402,Interlink Electronics FSR® 400 Series is part of the single zone Force Sensing Resistor® family. Force Sensing Resistors, or FSR's, are robust polymer thick film (PTF) devices that exhibit a decrease in resistance with increase in force applied to the surface of the sensor. This force sensitivity is optimized for use in human machine interface devices including automotive electronics, medical systems, industrial controls and robotics.

## Features¶

• Analog output
• Reliable mechanical structure
• High durability:

Tested to 10 Million actuations, 1kg, 4Hz / -10% average resistance change

## Specification¶

Item Value
Working voltage 3.3V/5V
Force Sensitivity Range 0.2N--20N
Force Resolution Continuous (analog)
Analog output 0-650
Non-Actuated Resistance >10 MΩ
Minimum Resistance 1 KΩ
Device Rise Time <3 Microseconds

Tip

If you want to measure the Non-Actuated Resistance, please remove this thing from the sensor

## Applications¶

• automotive electronics
• medical systems
• industrial controls
• robotics.

## Hardware Overview¶

### Schematic¶

This module use a DC-DC chip XC6206P332MR to provide a stable 3.3V, as you can see we called it 3V3. You can consider the Force Sensor J1 as a variable resistance, let's say Rf. The greater the pressure, the smaller the Rf value.

There are two parts in the picture above, for the left part:

$$VIN = \frac{3.3*30K}{30K+R_f}$$

For the right part, it's an Emitter follower, we use the amplifier U1 to isolate the pre-stage and post-stage circuits.

$$Vout = VIN$$

So, the output is:

$$Vout = \frac{3.3*30K}{30K+R_f}$$

Tip

In this section we only show you part of the schematic, for the full document please refer to the Resources

## Platforms Supported¶

Arduino Raspberry Pi BeagleBone Wio LinkIt ONE

Caution

The platforms mentioned above as supported is/are an indication of the module's hardware or theoritical compatibility. We only provide software library or code examples for Arduino platform in most cases. It is not possible to provide software library / demo code for all possible MCU platforms. Hence, users have to write their own software library.

## Getting Started¶

### Play With Arduino¶

#### Hardware¶

Materials required

Seeeduino V4.2 Base Shield Grove-Round Force Sensor(FSR402) Grove-LED
Get One Now Get One Now Get One Now Get One Now

Note

1 Please plug the USB cable gently, otherwise you may damage the port. Please use the USB cable with 4 wires inside, the 2 wires cable can't transfer data. If you are not sure about the wire you have, you can click here to buy

2 Each Grove module comes with a Grove cable when you buy. In case you lose the Grove cable, you can click here to buy.

• Step 1. Connect Grove-Round Force Sensor(FSR402) to port A0 of Grove-Base Shield.

• Step 2. Plug the Grove-LED to port D3 of Grove-Base Shield.

• Step 3. Plug Grove - Base Shield into Seeeduino.

• Step 4. Connect Seeeduino to PC via a USB cable.

Note

If we don't have Grove Base Shield, We also can directly connect this module to Seeeduino as below.

Seeeduino Grove-Round Force Sensor(FSR402)
5V Red
GND Black
Not Conencted White
A0 Yellow
Seeeduino Grove-LED
5V Red
GND Black
Not Conencted White
D3 Yellow

#### Software¶

Note

If this is the first time you work with Arduino, we strongly recommend you to see Getting Started with Arduino before the start.

• Step 1. Open the Arduino IDE and create a new file, then copy the following code into the new file.
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 /* How to use a Force sensitive resistor to fade an LED with Arduino More info: http://www.ardumotive.com/how-to-use-a-force-sensitive-resistor-en.html Dev: Michalis Vasilakis // Date: 22/9/2015 // www.ardumotive.com */ //Constants: const int ledPin = 3; //pin 3 has PWM funtion const int sensorPin = A0; //pin A0 to read analog input //Variables: int value; //save analog value void setup(){ pinMode(ledPin, OUTPUT); //Set pin 3 as 'output' Serial.begin(9600); //Begin serial communication } void loop(){ value = analogRead(sensorPin); //Read and save analog value from potentiometer Serial.println(value); //Print value value = map(value, 0, 1023, 0, 255); //Map value 0-1023 to 0-255 (PWM) analogWrite(ledPin,255-value); //Send PWM value to led delay(100); //Small delay }
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