2Digit up/down Counter

Posted on Feb 6, 2014

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 project shows what can be done with a micro and you can modify

2Digit up/down Counter
Click here to download the full size of the above Circuit.

it to set an alarm at any count-value or set a limit such as "count-to-60. " 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 "multiplexed (time-sharing). " The experimenter PC Board shows the five "In Circuit Programming" 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. Check the circuit by removing the chip and taking pins 6 and 18 to the 5v rail ad make sure segment "A" illuminates. Do the same for all the other segments. All the "lines" or "wires" 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. ;* ;* 2 Digit UP / Down Counter 17/6/2009 ;Port B drives two 7 segment displays ;Up Sw on RA2 Down Sw on RA3 ;"Units" drive on RA0 "Tens" drive on RA1 ;* * ;* list P = 16F628A ;microcontroller include ;registers for F628A _Config _cp_off & _lvp_off & _pwrte_on & _wdt_off & _intRC_osc_noclkout & _mclre_off ;code...

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