Q4. A 16F887 microcontroller is to be used as the basis of a greenhouse climate controller. It has the following sensors, actuators, and interfaces: Interface ADC ADC | Sensors Description | Temperature | LM35 outputs linear signal at 10mv/C Soil Outputs a linear signal in the range OV (very Moisture dry) to 4.5V (saturated) Humidity HDC1000 provides relative humidity (0-100%RH) measured with an accuracy of 13%; Pressure The piezoresistive pressure sensor capable to measure pressure (260-1260 mbar) 120 | 12C Actuator (All activated by a logic signal) Water Sprinkler Heater | Artificial Light Source | Interface LED Keypad LCD Description Indicates that the control function is active 4x3 keypad for data selection 16x2 LCD to display selected data The control system monitors soil moisture, temperature, humidity, pressure and activates the actuators as necessary. Operational settings can be varied by the user through the user interface. The system is to be powered by a 5V source, while actuators receive their power independently. (a) Draw a design for the microcontroller circuit, in the form of a detailed circuit diagram. Include all aspects necessary to make a complete and working circuit. Each sensor, actuator, and interface may be shown as a block, connected as appropriate to the microcontroller. The 16F887 pin connection diagram is given in Fig. Al in Appendix 1. In drawing your circuit, it is not necessary to draw microcontroller pins which have no connection made to them. [11 Marks] (b) Explain briefly but clearly all design decisions you make, and include any design calculations. If the information given is not enough to complete a design detail, explain the reason. [10 Marks] (C) Explain briefly how Ports A, B, C and D will need to be configured for your design. [04 Marks] 4- Q4. A 16F887 microcontroller is to be used as the basis of a greenhouse climate controller. It has the following sensors, actuators, and interfaces: Interface ADC ADC | Sensors Description | Temperature | LM35 outputs linear signal at 10mv/C Soil Outputs a linear signal in the range OV (very Moisture dry) to 4.5V (saturated) Humidity HDC1000 provides relative humidity (0-100%RH) measured with an accuracy of 13%; Pressure The piezoresistive pressure sensor capable to measure pressure (260-1260 mbar) 120 | 12C Actuator (All activated by a logic signal) Water Sprinkler Heater | Artificial Light Source | Interface LED Keypad LCD Description Indicates that the control function is active 4x3 keypad for data selection 16x2 LCD to display selected data The control system monitors soil moisture, temperature, humidity, pressure and activates the actuators as necessary. Operational settings can be varied by the user through the user interface. The system is to be powered by a 5V source, while actuators receive their power independently. (a) Draw a design for the microcontroller circuit, in the form of a detailed circuit diagram. Include all aspects necessary to make a complete and working circuit. Each sensor, actuator, and interface may be shown as a block, connected as appropriate to the microcontroller. The 16F887 pin connection diagram is given in Fig. Al in Appendix 1. In drawing your circuit, it is not necessary to draw microcontroller pins which have no connection made to them. [11 Marks] (b) Explain briefly but clearly all design decisions you make, and include any design calculations. If the information given is not enough to complete a design detail, explain the reason. [10 Marks] (C) Explain briefly how Ports A, B, C and D will need to be configured for your design. [04 Marks] 4
