Force Sensor RP-C18.3-ST

Force Sensor RP-C18.3-ST

20gr/6kg 18mm Diameter Round Button Resistive Thin Flexible Film Pressure Sensor Analog Output Pressure Force

     RP-C18.3-ST is a flexible thin film force (pressure) sensor, 0.4mm thick, with an 18.3mm diameter round shape. It detects force between 20gr and 6kg: with no force applied its resistance is above 10MΩ, at the 20gr trigger force it drops below 200kΩ, and it keeps decreasing as the force increases. The response time is below 10ms; it detects both static and dynamic loads.

     The bottom layer of the sensor has interdigitated conductive traces, the top layer has a pressure sensitive film. When the sensing area is pressed, the top layer closes the open circuit underneath and the resistance between the two legs decreases with the force. The force is read from an analog input (ADC) by making a voltage divider with a resistor; no separate supply or module is needed.

     "ST" is the short-leg version: together with the two short metal legs coming out beside the sensing circle, the total length is about 32mm. Thanks to its thin and flexible structure it can be placed under a seat cushion, a shoe insole, a gripper fingertip or a flat button.

Key features:

     20gr - 6kg detection range: Detects force from a light touch up to a strong press by hand; triggers at 20gr.

     0.4mm thin, flexible film: Takes almost no space; unnoticeable when placed under a cushion, insole or cover.

     18.3mm round sensor: Suitable for contact points the size of a fingertip or a small button.

     Fast response: With a response time below 10ms it detects the moment of touch, hit and grip without delay.

     Long life: More than 1 million presses; drift under a 24-hour static load is below 5%.

Features:

• Product type: Thin film resistive force (pressure) sensor, short leg
• Model: RP-C18.3-ST
• Detection range: 20gr - 6kg
• Trigger force: 20gr (resistance below 200kΩ when triggered)
• Initial resistance (no load): above 10MΩ
• Output: resistance; decreases as force increases (read as analog with a voltage divider)
• Response time: below 10ms
• Measurement: static and dynamic force (dynamic measurement at 10Hz)
• Hysteresis: about 10% (at 1000gr force)
• Drift: below 5% (24-hour static load)
• Connection: 2 short metal legs, non-polarized
• Operating temperature: -40°C - 85°C
• Lifetime: more than 1 million presses
• Sensor diameter: 18.3mm, round
• Thickness: 0.4mm
• Material: Flexible thin film, conductive traces and pressure sensitive layer
• Dimensions: about 32mm x 19mm (legs included)
• Weight: less than 5gr

Usage information:

• Connect one leg of the sensor to 3.3V or 5V, and the other leg both to the analog input and through a resistor to GND (voltage divider). As the force increases, the voltage at the analog input rises. Choose the resistor value according to the force range you want to measure; a few kΩ up to about 10kΩ is a common starting value.
• The force must fall inside the sensing circle. Place the sensor on a hard, flat surface; use a small flat washer or disc smaller than the sensing area to spread the force evenly.
• The reading is not linear with force; if you need a result in kilograms, make your own calibration table with known weights.

Applications:

•  Seat and chair occupancy (someone seated / not) detection
•  Bed occupancy and getting-out-of-bed alert
•  Smart shoe insole and pressure point measurement
•  Grip force in robot hands and gripper fingers
•  Rehabilitation and hand grip strength tracking setups
•  Game controller and pressure sensitive key
•  Electronic drum pad and hit detection
•  Touch button and switch working by press strength
•  Door, lid and drawer closing detection
•  Object present / absent detection on a shelf or in a box

Things to consider:

•  This sensor is not a precision scale or load cell. Its hysteresis is about 10%; it is suitable for detecting the presence and approximate strength of a force, gram-level measurement needs a load cell.
•  Do not heat the film part while soldering the legs; solder quickly or plug them into a female connector. Do not bend or pull the point where the legs join the film.
•  Force above 6kg, sharp pressure or pressure extending outside the sensing area can damage the sensor. Do not press with sharp objects, do not cut or pierce the film.
•  The sensor does not produce a voltage by itself; it must be connected to an analog input with a voltage divider resistor.

Package contents:

•  1 Piece Force Sensor RP-C18.3-ST
•  Note: Voltage divider resistor, connector and cables are not included in the package.