Week -2

1. Make a Simulink model of Doorbell using solenoid block with the following details:

Program :-

Output :-

• In graph there is three plot. First of ON-OFF pulse signal as 1 means ON and 0 means OFF battery. Second is plunger velocity. And thisrd is plunger displacement.
• As per requirement battery is connected for 2 second by giving 1 value to ON-OFF switch by pulse generator. So, after battery connection emf is produce in solenoid which can attract and displace plunger so velocity is sudden increase and plunger vibrates and take time to stable and velocity become zero. Thats why velocity cirve is showing wave less than 1 second take to become stable.At the same time plunger displace as shown in third graph. Displacement also show wave because of vibration.
• When bell ring finally.
• After 2 second pulse give 0 signal to switch which is disconnect battery with solenoid till next two seconds. So plunger retard back to its original position and also it is again vibrate. So, volocity is showing again wave and displacement is also waving and become stable at its original position.
• This two same processes are reapeat one after another in every two seconds. And bell is ringing and become silent.

2. Use a thermistor to sense the temperature of a heater & turn on or turn off the fan.

Program :-

Condition 1 :- Temprature below 25

Condition 2 :- Temprature above 25

Output :-

• As per program requirement Temperature source: 20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds which is clear in above plot.
• In this program heat source is transfer heat by convection to thermistor sensor. Thermistor resistance is variable with temprature so voltage output vary with different temprature. So we use voltage as thresold value which is 0.012V to ON/OFF fan. Also sensor add to check temprature of heat source.
• In above graph there us three plot. One of Temprature from heat source. Second for voltage vary with respect to time because of temprature. Third is for ON/OFF signal indication.
• As per requirement temprature is 25 to become 20 for 10 second which is decreasing hyperbolically. As temprature decrease it increase resistance of thermistor so voltage is decreae as same as temprature from 0.012V. During this time temrature is below 25 so fan will not start.
• After 10 second, Temprature is increase and being 27 for 10 to 30 second. Temprature is increasing slowly from 20 to 27 and become stable. With that thermistor resistance is decrease and voltage is increase near to 0.013 from 0.012V. Fan ON/OFF signal is 0 till 13 second at which sysem temprature cross value of 25. Then signal is activated and give value of 1 which means fan is started.
• Between 30 to 50 second temprature is deacreased 27 to 25. Which is also decrease gradually. Also voltage is drop to 0.011V. When temprature goes below 25 ON/OFF switch give command to fan to stop. Which is at approx 32 second. Then fan is become OFF.
• So, like this ON/OFF command is give to Fan to maintain temprature.