19 Aug Weight Sensor Signal Conditioning You should provide a detailed description including circuit diagrams and relevant design calculations explaining how the two weight sensors will be
Weight Sensor Signal Conditioning (20%)
You should provide a detailed description including circuit diagrams and relevant design calculations
explaining how the two weight sensors will be interfaced with the PIC18F4455 microcontroller. You
should explain the rationale for the design and how it is makes optimal use of the available feature
of the microcontroller. You should identify suitable weight sensor and provide relevant calculations
and data.
Weight Control System Design Notes (10%)
You will carry out design work on the code and produce a set of design notes which may include:
• a flow chart of the operation of the program,
• a list of the I/O pin allocations
• A list of the subroutines you will use.
• Pseudocode outline for your program
Microcontroller Code (20%)
You should provide PIC18F2455 code to implement the required functionality. All code should be
appropriately commented and presented in a professional fashion using appropriate formatting and
indentation. You may write the program in Assembly Language OR C code suitable for the XC8
compiler.
Scenario
You have been contracted to develop a control system for a packing system which will load potatoes into plastic punnets based on weight. Potatoes are to be loaded into punnets until the weight of the punnets is 1kg +/- 100g.
Each potato will weigh between 80g and 110 g. The potatoes will be delivered one at a time on a conveyor belt with a minimum separation of 10cm between each potato. When operational the conveyor will move at a speed of 5cm/s. When the potatoes reach the end of the conveyor, they will fall into a hopper which is equipped with a load cell. The load cell will produce a voltage which is directly proportional to the weight contained in the hopper. The output voltage will be 10mV per 5g.
The hopper will be controlled by two servos. If servo ‘A’ is activated the potato in the hopper is emptied into the punnets. If servo ‘B’ is activated the potato is returned to the beginning of the system. The punnets are carried on a second conveyor belt system at a spacing of 20cm. This belt moves at a speed of 4cm/s. The punnets currently being loaded is weighed by a further load cell with the same operational parameters as that for the hopper.
