Question

Design, build and test a sensor that measures forearm rotation (pronation and supination)

Equipments: potentiometer
Goniometer
Tape,glue

Could you please help me getting the idea ?

Answer 1

Before starting, I want to explain two things:

• A Goniometer has two arms, stationary arm and the moveable arm . It is used to measure the angular difference .
• A Potentiometer is basically a 3 terminal ( i.e V_cc, Signal and ground) variable resistor. So if the rotating part of the potentiometer moves, the resistance also changes in between signal and ground terminal.

The project can be done in 2 ways:

1. Equipment needed: Potentiometer, Goniometer, Tape, Glue, DC power supply, Voltmeter.

• Attach the movable part of the potentiometer at the joint section of the 2 arms with the help of glue such that when there is a angular difference happening between two arms(i.e one arm is moving with respect to another one), the movable part of the potentiometer also moves.
• Provide a input supply(i.e 12 v) in between V_cc and ground terminal then take the voltage output from signal and the ground terminal. So that if it moves then the voltage output changes between 0 to 12 volt in between signal and ground terminal..
• (If you want to measure the exact rotation angle by means of the voltage--> follow this step or else skip to the next point) Measure for each 1 degree deviation, how much voltage difference is there. After that you can calculate for a given voltage, how much angle deviation occurs.( Let's say for each 1 degree deviation of angle, the voltage change is A volt. Now for a certain angle voltage is showing B volt. To calculate the angle for B volt---> The angle = B/A degree.)
• ( If you want to sense whether it is moving only--->) If one arm moves to either direction, the potentiometer movable part also moves, either you will see the voltage is getting higher or lower at the signal terminal. By studying whether the voltage is getting higher or lower, you can sense the direction of the motion.
• Now attach the Goniometer's one arm to a fixed position and the another arm to a movable position (i.e forearm) with the help of Tape.
• Now whenever it moves, you can find it by voltage measurement.

2. Equipment needed: Potentiometer, Goniometer, Tape, Glue, Ohm meter.

• Attach the movable part of the potentiometer at the joint section of the 2 arms with the help of glue such that when there is a angular difference happening between two arms(i.e one arm is moving with respect to another one), the movable part of the potentiometer also moves.
• Attach a Ohm meter in between Signal and ground terminal of the potentiometer. So that if it moves then the resistance changes high to low or low to high.
• (If you want to measure the exact rotation angle by means of the resistance--> follow this step or else skip to the next point) Measure for each 1 degree deviation, how much resistance difference is there.After that you can calculate for a given resistance, how much angle deviation occurs.( Let's say for each 1 degree deviation of angle, the resistance change is A ohm. Now for a certain angle, resistance is showing B ohm. To calculate the angle for B ohm---> The angle = B/A degree.)
• ( If you want to sense whether it is moving only--->) If one arm moves to either direction, the potentiometer movable part also moves, either you will see the resistance is getting higher or lower at the signal terminal. By studying whether the resistance is getting higher or lower, you can sense the direction of the motion.
• Now attach the Goniometer's one arm to a fixed position and the another arm to a movable position (i.e forearm) with the help of Tape.
• Now whenever it moves, you can find it by resistance measurement.

I hope this will help you, Thank you.