Led Clock

12Hr Led clock using 16F84 or 16F628. Also, schematic to build a Jumbo clock is included. (6/05/2004)
16F84 version have a problem, pending to be fixed. Updated! (9/6/2006)


CODE: JP6282/JP841 - PIC: 16F628 or 16F84A


Using only 2 capacitors, 3 resistors, 4 seven-segment Display, 1 xtal, 2 switches n.o. and 1 Microcontroller PIC, you can build this Digital Led Clock. you can use common anode or common cathode display, just select the display type. Here is the pinout information:


led_clock/JP6282DS.gif Led Clock Schematic


Pin 3 defines the display type. If you will use common cathode display, connect to negative. For common anode, connect to positive. Here is a example circuit:


led_clock/JP6282.gif Led Clock Schematic


Please note: the pin 4 requieres a 10k resistor ONLY for 16F84. On 16F628 is not connected. The minutes displays are upside down.


For the capacitors, I used 30pf. You have to read the xtal manufacturer specifications to know the capacitor value recommended. Short connections on xtal is a must to keep accuracy.


Download the Digital Led Clock HEX code 16F628 version HERE
Download the Digital Led Clock HEX code 16F84 version HERE


I built some clocks using this circuit. 2 Wall clocks and a Desktop clock. Every digit is 3 inches high, every segments are 3 led in series. The voltaje used is 5.5 volts (1.8volts x 3 = 5.4 Volts) Leds aren't really bright but works great. Here is the pictures of my wall clocks:


Wall clock using 16F628
Wall clock using 16F628


Here is a desktop clock:


Desktop clock using 16F628


Feb 16, 2005. - UPDATE: If you want to build a clock with a big display, you have to add a non-inverting CMOS buffer. Here is the schematic to build a "jumbo" clock:


Jumbo clock schematic


Dec 4, 2005. - ERRATA: DO NOT USE 74HC541 FOR 12 VOLTS! is better to use 4050 CMOS. Some big 7-segment display works with 12 Volts. - Thanks Mark Efkowitz!


9/6/06 - Updated: Here is the schematic using CMOS 4050 instead of 74HC541. Sent by Flash Gordon.



This schematic is only a sample. You can connect the 4050 to 12V and drive jumbo displays. Do not connect regular (small) LED displays to 12 volts because the circuit may overheat. Please read the manufacturer specification of your displays. - Thanks Flash!


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