AJAX Electronics - NET PIC Clock



Menu:	NET Clock - Microcontroller Version
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• Other	Introduction:
	This project is an extension of my discrete-IC New Earth Time clock. The goals of this project were to reduce component count, increase timekeeping accuracy, and allow future improvements and features (GMT/NET conversions, etc).

	Background:
	For more information on New Earth Time, please visit http://www.newearthtime.net The current New Earth Time is:
	Design:
	For this project, I selected the Microchip PIC 16F627a becuase a) it is very inexpensive and b) it has a suprising number of features, several of which are used in this clock. Timekeeping is performed with an external 32.768kHz "colorburst" crystal on Timer 1 (TMR1). Timer 1 runs independently of the main system clock, and generates an interrupt on every new earth time minute. What's also nice is that TMR1 will continue to run even with the PIC in sleep mode. I envision this feature will come in handy for the planned NET watch, or possibly for keeping time during a power outage from only a small backup capacitor. I used the internal 4MHz oscillator for the remainder of the program functionality, none of which is time-critical. The 7-segment displays are multiplexed and scanned on an interrupt from Timer 0 (TMR0), allowing for minimal display flicker. The time setting switches are also multiplexed on PortA pins 0-5. Presently only two buttons are needed (for time setting), but I wanted to allow for future expansion. You can download the latest code version here: net_pic_main_v2_0c.asm The schematic diagram for the NET PIC Clock is below, as well as a picture of the NET PIC Clock during development: (click to enlarge image)

	Final Touches:
	I assembled the prototype clock in a case which used to house the controls for a heated mattress, giving it a "retro-modern" look. The Degrees LED is just a standard LED with heatshrink around the lens (to confine the light), and a few applications of a sharpie marker in the center to blank out the center. Here are some pictures of the finished prototype: (click to enlarge image)
	$\net_pic_clock\net_pic_front.JPG$ $\net_pic_clock\net_pic_front_unc.JPG$ $\net_pic_clock\net_pic_rear.JPG$ $\net_pic_clock\net_pic_rear_unc.JPG$ $\net_pic_clock\net_pic_side_unc.JPG$

	Coming soon: PCB Artwork, and a NET Watch!
	Page Last Updated: 12/3/06. E-Mail: Page Contents © 2003-2006 by Andrew J. Cleary, AJAX Electronics

NET Clock - Microcontroller Version