You are working for a robotics company that requires you to construct a sensor to measure the angular rotations of a robotic arm that has a range of rotation of 270 degrees. Given that you have the following equipment available:
- An RTD that is corrupted by noise. Its dissipation constant is 30mW/oC. Its resistance at the nominal temperature of 65o is 150O. Its fractional change of R with temperature is 0.004/oC.
- A rotary potentiometer with a diameter of 10cm and a coil diameter of 0.5mm.
- Capacitors, inductors and Resistors of any size.
- An FSR that is corrupted by noise,
- A 2V voltage source,
- A 1 A current source,
- Different types of LED,
- Piezoelectric sensors,
- An 8 bit ADC with (a dynamic range between 0V and +10V)
- An instrumentation amplifier,
- A summer amplifier,
- A buffer amplifier,
- Inverting and non-inverting amplifiers,
- An LVDT,
- An IR sensor.
1) Propose a sensor of the above list that can measure angular rotations of the arm. Given that the diameter of the robot arm is 20cm, what is the smallest arc length the arm can move through?
2) How would you connect this sensor? Explain the non-linearity issue that you might get and you can reduce this effect.
3) It is known that loading is a problem in such a system. How would you design your circuit to reduce the effect of loading?
4) Two types of noise are apparent in such a system: (1) external noise that is common to both the source and reference leads and (2) another high frequency noise (2MHz) that is carried with the signal. How would you eliminate the first source of noise? How would you eliminate the 2nd noise? Design a circuit to attenuate this 2nd source of noise to 1%. What effect does this have on the maximum frequency component of the signal which is 3kHz?
5) Design a circuit to interface the output of (4) to a computer. If you do analog to digital conversion don’t forget any amplification and offset that might be necessary for interfacing the circuits. Also define the properties of this analog to digital converter (Offset, span, step size, resolution). Draw a diagram of the entire system including all the components from (2), (3), and (4).
6) What rotation does an output of 11100010 of the ADC correspond to?