Week -2

AIM :

1.To make a simulink model using solenoid block with the following details.

2.To use a thermistor to sense the temperature of a heater and turn on or turn off the fan as per the below conditions.

CONDITIONS:

1.DOORBELL : According to the given condition, we have to keep the switch closed for 2 seconds and then release the switch.

In the above simulink model, we have a battery, which is the voltage source in the circuit. There is a switch which opens and closes the circuit, a solenoid block to which the translation motion sensor is connected. The input is given from the pulse generator block to the switch. The switch block is a type of block which is closed when the recevied input is above the threshold value. If the input is below the threshold , the switch block will be open. The output is obtained from the translation motion sensor in the Scope block, where we have a plot of the movement of the arm(plunger). Also there is a Solver configuration block. Keeping the solver configuration block is necessary to use Electrical and mechanical references when the respective blocks from the block-sets are used.

2.THERMISTOR : FAN CONDITIONS - ON if the temperature is above 25°C, otherwise OFF. (Temperature source 20°C from 0 to 10 seconds, 27°C from 10 to 30 seconds, 23°C from seconds).

In the above Simulink model, we have a battery, which is the voltage source in the circuit. There is Controlled temperature source, a Thermistor and a resistor. A thermistor is basically a resistor whose resistance depends on the temperature. In this case we have a NTC (Negative Temperature Coefficient) type thermistor. For NTC thermistors, the resistance decreases as the temperature increases. The resistor is of a known resistance which is used to know the threshold value of the thermistor. A voltage sensor block (Voltmeter) is also connected between the two terminals of the resistor. The physical signal output from the voltage sensor is given to a Switch block through the output plot is obtained in the scope. We also have the Solver configuration block. Since we have blocks from Thermal and Electrical block-sets, we have connected Thermal reference and Electrical reference. The input for Controlled temperature source is given through the Signal builder block which generates signals as designed in the block manually.

EXPLANATION :

DOORBELL: The input pulse generator block is given to the switch block through the PS-Simulink converter. It is used to convert physical signals to Simulink signals. When the input is more than the threshold value is given in the switch block, the switch is closed and the circuit is complete. When the circuit is complete and closed, the current flows through the coil. Through the solenoid, the iron core inside excites and the movement of the arm is facilitated. The movement is detected by the Translational motion sensor block. The output from the sensor block is again converted to Simulink signal using the PS-Simulink converter and sent to the Scope where the plot is obtained.

THERMISTOR: First the threshold for the found out by giving the temperature input at 25°C. When the threshold is found, the signal is built in the signal builder and the same is given as input to the Controlled Temperature source through the Simulink-PS converter. This is done to convert the Simulink signal to a physical signal. One port in the source is given to the Thermistor and the other port is used for Thermal reference. In the main circuit, we have a battery which is the voltage source of 12V. The position of the battery is connected to the positive of the Thermistor and the negative of the Thermistor is with one terminal of a resistor which is known resistance. A voltage sensor block is connected across the terminals of the resistor. The physical signal output from the voltage sensor is block is given to the Switch block. We can see that the voltage sensor is connected in parallel combination with the resistor. In the first scope image below we can see that the varying temperatures at different time intervals. According to the given conditions we can see that when at temperature above 298 K the switch turns ON and can be given a particular threshold value.

CONCLUSION : Thus the Simulink model is done and the required output is obtained in the form of plots.