Week -2

Door bell system:

Input:

Aim of the project is to generate bell ringing by moving the arm and retracting it back.

• Pulse generator is used as the input to generate the signal.
• Amplitude is set to 1 and period is set to 4 secs.
• Pulse duration is set to 50% (Half of Period - 2 secs). This results in pulsed output ON for 2 secs and OFF for 2 secs.
• Battery source of 12V is used.
• Solenoid of pulling outwards type is configured. (i.e moving away from Port C).
• Solenoid and battery is connected using a Physical switch. The input to the switch is the Pulse generator.
• Electrical reference and Mechanical translation reference are given for solving the equation.

Process:

• As the Pulse generator generates signal for 2 secs, Switch is closed.
• This causes the solenoid to be pulled in, which results in arm movement and the arm hits the bell.
• After 2 sec, pulse generator is OFF, which results in Switch being opened.
• This results in Solenoid arm being retracted back and hence the arm moves back from the bell.
• The above procedure is repeated (hitting the bell for 2 sec and idle for 2 sec) which results in bell ringing.

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Thermistor:

Input:

Aim of the project is to switch ON the Fan, when the input temperature crosses 25 deg C (298K) and to switch it OFF when the temperature drops below 25 deg C (298K).

• Repeating sequence stair is used to generate the signal which is as follows.
  • 0-10 sec --- 293K
  • 10-30 sec --- 300K
  • 30-50 sec --- 296K
• Controlled temperature source is used to direct the Heat input to the thermistor.
• Battery source is used, + terminal of which is connected to Voltage sensor and then further to Thermistor +ve.
• Battery negative is connected to Thermistor -ve. Voltage sensor is connected across the battery (Parallel connection).
• Switch block to decide what action to take, either to swich ON the Fan or switch OFF.
• Controlled Voltage source to power the DC motor (Fan).
• DC Motor (which is Fan here)
• Ideal Rotational Motion sensor to determine the motion of the Fan.
• Electrical reference and Mechanical rotation reference for solving the equation.

Process:

• Initially the voltage at which the Temperature is 298k is checked, by giving constant input signal to Controlled Temperature source. i.e 298k as the input temperature. At this temperature, the corresponding voltage is measured, which is 11.976 V.
• This 11.976 V is the deciding factor, for the Switch to function.
  • If the temperature is above 298K, the voltage will drop below 11.976 V, so at this condition, Fan to be turned ON, this is set to Constant value of 1.
  • If the temperature is below 298K, the voltage will raise above 11.976 V, so at this condition, Fan to be switched OFF, this is set to Constant value of 0.
• The output of Switch is connected to Controlled volatage source, which switches ON the motor as the input signal is 1 and switches OFF the motor as the input signal is 0, which is measured in the Ideal rotational motion sensor as 1500 rad/s.(When Fan is ON)
• So as the temperature increases, the resistance of the Thermistor decreases.