This notion page has the materials for the 2022 summer research project. Useful links to learn more about the project are given below.
FSR stands for "force-sensitive resistor." It is a type of sensor that measures pressure, force, or weight by detecting the amount of electrical resistance generated by the applied force. FSRs are typically made of a flexible, pressure-sensitive material, such as a thin film of conductive ink or a polymer. The goal is to use a Force Sensitive Resistor to find a relation between the voltage and force the gripper applies.
We connect the force-sensitive resistor (FSR) in a voltage divider configuration. This allows for measuring a slight change in resistance caused by force or pressure applied to the sensor. The FSR is typically connected in series with a fixed resistor, and the voltage across the FSR is measured to determine the amount of force applied.
(a) Voltage Divider Configuration of an Op-Amp
In a voltage divider configuration, the output voltage is divided between the two resistors based on their relative resistance values. When no force is applied to the FSR, its resistance and output voltage are low as force is applied to the FSR, its resistance decreases, and the output voltage increases. In this case, $R_1$ is the FSR and has a resistance range of up to 10MΩ, and $R_2$ was chosen as 10kΩ to capture the full range of $R_1$.
The voltage divider configuration allows the FSR to be used as a transducer, converting a mechanical force into an electrical signal that can be measured and processed by an electronic circuit. This configuration allows for easy interfacing with microcontrollers such as Arduino.
The selection of an operational amplifier (op amp) to use with a force-sensitive resistor (FSR) will depend on several factors, including the desired gain, input impedance, and output swing of the circuit, as well as the voltage and current requirements of the FSR.
Since we are using an FSR in a voltage divider configuration, we should choose an op-amp with a high input impedance to minimize loading on the FSR. Additionally, we need to consider the voltage swing that the op-amp can handle and the FSR's voltage and current requirements.
(b) LM324n Op-amp
After checking the datasheet of the FSR, op-amps such as LM324n, LM741CN and LM358 were found to be the most compatible with our use case.