Week -2
Solution:
- Make a Simulink model of Doorbell using solenoid block with the following details:
Answer:
To solve this, it is assumed that a solenoid will act as a doorbell plunger. It is 12V DC rated and to trigger it on, a pulse generator is configured to create signals to make a switch turn on and off.
Steps:
1. A solenoid block is taken and is connected in a circuit with a switch and a DC battery. All the parameters of this block are kept as by default, only the rated voltage is made 12 V to match with the voltage of battery. Electrical reference and a solver configuration is added to simulate the model.
2. We need to observe the movement of solenoid plunger as well, to do so a translational motion sensor is used and its output point is connected to a scope. In order that the scope should read and understand the signal from simscape environment, a PS to Simulink converter is added before scope input. A mechanical reference point is important to be added and connected with the reference point in order to run the simulation.
3. A signal has to be craeted by which we can turn on and off the switch, which in turn operate the solenoid coil on and off. This is done through a pulse generator, in which we can set the on time, off time, on delay, amplitude of the signal. Output signal of pulse generator is in simulink environment, while the switch used is of simscape environment, in order that there should be proper communication in between these two things, a Simulink to PS converter is connected in between output of pulse generator and input of switch.
4. After running the simulation, it is observed that there is movement of the solenoid plunger in and out, but at the same time it is seen that there are oscillations caused due to inertia and damping constants of the solenoid unit. We can get rid of these unwanted oscillations by playing with the damping values of the solenoid to make this system more efficient.
2. Use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per the below conditions:
To solve this, a thermistor is to be connected in a circuit, its output, the change in resistance is to be used as an input for a fan to make it on or off, and the thermistor is supposed to sense the changes in the ambient temperature. A toggle switch is used as a repesentation of a fan.
Steps:
1. Created a circuit with a thermistor, a DC voltage source, and a normal resistor. The voltage drop across this resistor will act as a threshold or trigger point for the fan (toggle switch) to get turn on or off. A voltage sensor is used to monitor this drop across the resistor. Value of resistor is kept as 10 ohms. An electrical reference and a solver configuration is used to run the simulations errorfree.
2. A toggle switch is used as a representation of a fan. Toggle switch is intended to toggle its status once the threshold limit is triggered, in this case the threshold limit is set as the voltage drop across the resistor connected in circuit with thermistor. A scope is connected to see the plot of all these happenings.
3. We have 3 cases, 20 deg C - 0 to 10 sec, 27 deg C - 10 to 30 sec and 23 deg C - 30 to 50 sec. To imitate these cases, a signal generator block is used, in which we can create a customised signal plot, which can be a swuare wave, a ramp or anything like that. here we have facility to change the range of X and Y axes as well. In this block a signal is craeted to match up with the cases given in problem statement.
4. This customised signal is to be fed into a temperature source, which in turn is supposed to mimic 3 different temperatures at three different times. These thermal blocks work in kelvin units of temperature measurements, hence firstly given tempearatures are converted into kelvin scale from deg celsius.
5. Once we have values of temperatures, we can eaasily create customised signal and connect it as a trigger into a controlled temperature source, again, it is going to be a simulink environment signal and to feed it into controlled temperature source, a Simulink to PS converter has been used. Also a temperature teference block is added and connected to terminal A.
6. A scope is connected after the signal generator to monitor the signal which is craeted is as per our requirement or not. once we run the simulation, an error was there regarding a solver configuration. I did not understand the error and took help of google to resolve it. It was something related to parameters of the simulink to PS converter block.
7. Once our model becomes errorfree, it was simulated and it can be seen that as per our given input signal, thermistor was responding to changes in temperatures and the corresponding voltage drop was appearing across the resistor connected in the series, this value was set a threshold point for the toggle switch and the scope connected after that switch was giving the desired result.