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Whilst building my Frequency Standard I found that I needed a frequency counter that I could permanently add to the project. Looking around the Net I found this little counter. It's known as the Weeder Counter after its author. Over the years it's been ported to different PIC's until eventually it was ported to the ubiquitous 16F84. The counter uses a 16x1 Hitachi HD44780 type LCD display. The site that I found it on had both the sources and the compiled hex as well as a PCB layout so that one could make ones own. The PCB is sized to attach directly to the back of the LCD making it a very compact device. Having downloaded the files I set about making the PCB. The first thing that I noticed was that the device runs on 5 volts. Not that unusual but a bit of a pain if one's bench supply is 12 volts. Before actually commiting the PCB to copper I modified the design such that it would allow for the addition of a 78L05 voltage regulator. My version of the PCB is that which is presented here. |
There are 2 variations to the source code. One is just a plain counter and the other has a user definable sign on message but is otherwise the same. When using your PIC programmer set the OSC to XT and disable the Watchdog Timer.
I'm not going to explain the parts list as it's very simple and can be seen on the layout drawing below. The only addition to the drawing is the 7805 (or 78L05) regulator and the LCD display. The parts in blue are installed under the board due to space limitations. Personally I ditched the 10K contrast pot and swapped the 47K resistor for a 4K7 resistor and placed it between pin 3 of the LCD and ground. The 10K/47K arangement serves only to adjust the contrast. It occurred to me that once it was set I wouldn't need to mess with it and so I did a bit of "select-on-test" and settled on a 4K7
© & ® Mark A Phillips, G7LTT 1995-2005
