This project comes via two circuits on 2 boards. The first circuit is designed around a PIC16F628A. It has been presented on an experimental PC board using surface-mount components and was built in less than 1 hour, with about 2 hours to write and finalise the program. See P1,  P2
The second circuit uses a PIC12F629 to produce a 2-Digit Up/Down Counter (see P3).
Both use âIn Circuit Programmingâ via PICkit-2.
P5 Describes the up/down counter displaying the âgearâ for motorcycles and racing cars.
The project shows what can be done with a micro and you can modify it to set an alarm at any count-value or set a limit such as âcount-to-60.â You can add a buzzer or relay or increase the display to 3 digits. You need to remember that each additional display will reduce the illumination of each digit as they are âmultiplexed (time-sharing).â
The experimenter PC Board shows the five âIn Circuit Programmingâ pins and a diode on the positive rail to drop the 6v supply to 5.4v. The board also has a 100n surface mount capacitor and two surface-mount transistors. The Up/Down buttons have 22k resistors. TESTING THE CIRCUIT
Check the circuit by removing the chip and taking pins 6 and 18 to the 5v rail ad make sure segment âAâ illuminates. Do the same for all the other segments.
The circuit diagram does not have any voltages marked on it as the circuit is DIGITAL.
All the âlinesâ or âwiresâ or pins of a microcontroller will have rail voltage (5v) on them when they are HIGH and when you come to a resistor, the resistor will drop a certain voltage. The voltage it will drop will be the difference between rail voltage and the voltage developed across the component it is driving. If it is driving a LED, the LED will drop a characteristic voltage of between 1.7v and 3.6v, depending on the colour.
If the component is a transistor, the voltage developed between the base and emitter will be about 0.7v.
For more detail: 2 Digit up/down Counter using PIC16F628A
About The Author
Ibrar Ayyub
I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.
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