Sterilization Unit
- 1. Microprocessor, Programming and Interfacing Design Problem P 28: Sterilization Unit Batch - B282 Report By:- Rohit Agrawal - 2012A8PS267G Ravi Bhushan - 2012A8PS328G Shikhar Jain -2012A8PS357G Rishikesh Bagwe -2012A8PS401G
- 2. Problem Statement The unit performs sterilization by increasing temperature to maximum value (xo C). This temperature has to be maintained for a maximum value for 2 minutes before it is brought gradually to a nominal temperature value (yo C). The time taken for bringing down the temperature can be varied between four different values as decided by user. A push button switch (level) is available for this purpose. The number of times the key is pressed decides the speed at which at which then temperature should be brought down. 1 Press – 3 Minutes 2 Press – 5 Minutes 3 Press – 7 Minutes 4 Press – 10 Minutes While sterilization process is taking place the door to the unit must remain locked. The door can be opened only when the user presses end. User Interface: Status LED glows as long as the sterilization process is being done. Once 30o C has been reached the LED goes off and the door mechanism unlocks. Once the door is closed again the temperature is brought back to 30o C.
- 3. Design Specifications Simple DC Motor : Nominal Voltage: 12 V Coil Resistance: 10 Coil Inductance: 100mH Zero load RPM: 500 Max Torque%: 50 Effective mass: 0.0000001 Heater: Ambient temperature: 25 Thermal Resistance to Ambient: 0.05 Oven Time Constant: 6 Heater Time Constant: 0.0001 Temperature coefficient: 1 Heating power: 2300 W 74LS138 :
- 4. 8255(PPI):
- 6. Components used: 8086(1) - Microprocessor 8255(1) - Programmable Peripheral Interface 8253(1) - Programmable Interval Timer 2732(2) - 4K ROM 6116(2) - 2K SRAM ADC0802(1) - Analog to Digital Convertor 74LS373(3) - Latch 74LS245(2) - Bidirectional Buffer 74LS138(1) - Decoder (3 to 8) 2- Simple DC motors L293D(1) – Motor Driver 1 - Heater 1 – Tri state buffer 1 – Toggle Switch 3 – Button Switches 3 - LEDs 6 – OR Gates 4 – NOT Gates ‘TIMER’ LED – Used to count the 2 minutes when the temperature reaches 80 deg C. And also the next user chosen time (3,5,7,10 mins) is calculated by this LED. 1 = Counting , 0 = Not Counting ‘ STATUS’ LED – 1 = Sterilization process is going on 0 = The process is over ‘DOOR’ LED – 1 = Door is locked 0 = Door is unlocked
- 7. Input/Output Port Mapping Port A : 00h Port B : 02h Port C : 04h Control Register : 06h Counter 0 : 08h Counter 1 : 0Ah Counter 2 : 0Ch Counter Control Register : 0Eh Memory Mapping: ROM1 => 00000H -01FFFH (4K) RAM => 02000H – 02FFFH (2K)
- 8. Assumptions: The Sterilization takes place at 80 deg. C. (xo C = 80o C) yo C = 30 o C The door should be closed manually. But it opens only when the user presses the END button. It opens due to a ‘DOOR’ motor IR(toggle switch)=0 => Door closed IR(toggle switch)=1 => Door open(toggling is done manually) FOR LEV1: Fan motor cools the sterilization unit from 80o C to 30 o C in 3 mins at 50% duty cycle LEV2: Fan motor cools the sterilization unit from 80o C to 30 o C in 5 mins at 33% duty cycle LEV3: Fan motor cools the sterilization unit from 80o C to 30 o C in 7 mins at 20% duty cycle LEV4: Fan motor cools the sterilization unit from 80o C to 30 o C in 10 mins at 10% duty cycle Remark(for Proteus Simulation) During Simulation, the turning on of FAN motor implies cooling and reduction in temperature. The temperature shown during this time by the heater reduces on its own(self cooling) and then maintains at 30 o C till the door is open. (For eg: If the user has chosen LEV2, the motor will run for 5 mins at 33% duty cycle and the stop but the temperature may or may not come to 30 o C since it is not connected to the motor)
- 10. Flow Chart of the Software