At the reset button, it have to make a parallel connection with the 220pF (104) ceramic capacitor. It is because to prevent multiple pulse give to the PIC16F877A. If the users press the reset button once, user has to wait the capacitor to be charged up before the second press. It is the law of capacitor to be charge and discharging. The knowledge of electronic components that student learn on previous semester have been applied.
2- LED and Resistor Priority
Simulation and actual device is not same. On the simulation, there are no tolerance and there are no disturbance. Everything are considered to be perfect. On Figure 3.9 there are a mistake that student do. For all know, the function of resistor is to prevent over current to LED. In this case, the circuit have to modified manually to avoid from making a new PCB. The arrangement of resistor and LCD are changed.
3- LCD
There are many type if 16x2 LCD. Each type of LCD have their own datasheet and connection. LCD must be grounded according to it’s pin. Wrong connection will display nothing except black and white screen on LCD. At first, student buy a VCM162A LCD. The result of the system is the LCD display a creepy character but it is working great on the other type of LCY which is JHD162A. With the insufficient time, the new LCD are replaced.
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