Eleven Output Free Running Clock Kit


Many circuits require a clock source and traditionally hobbyists have used either a crystal oscillator or the classic 555 in conjunction with counters. It always seems as if all of this is a good deal of effort and I know I have abandoned more than a few ideas as just the thought of wiring the clock circuitry left me weary.

This kit uses a programmed Microchip PIC in an 18-pin DIP to provide 11 free running clocks. Note that this is a kit of parts suitable for assembly on a solderless breadboard. A printed circuit board is not provided.


The programmed PIC provides 11 free running clock outputs having periods of 1, 10 and 100 ms, and 1, 10 and 30 secs and 1, 5, 10 and 30 minutes and 1 hour. The duty cycle is 50 percent. Thus the one hour clock output is in a logic one state for 1800 seconds and then in the other state for 1800 seconds.

A /GATE input on the PIC is provided. When at logic one (or open), all clock are off. The clocks are turned on when the /GATE input low.

A POL input is also provided which defines the initial state of all clock outputs when /GATE is first brought low.

When the POL input is at logic one (or open), are 11 clock outputs are at zero when the system is idle (/GATE is high). When /GATE goes low, all clocks begin the first half period in a one state. When the POL input is at a logic zero, the idle state of all clock outputs is a logic one. When the /GATE input initially goes low, all clock outputs begin the first half period in a zero logic state.

For example, if /GATE is high and POL is high, the processor is idle and all clock outputs are at a logic zero. When /GATE goes low, all clock outputs start in the logic one state for the first half period.

When /GATE goes high, all clock outputs immediately return to the idle state.

Thus if /GATE is high and POL is low, the "one hour" output is idle at a logic one. When /GATE goes low, the "one hour" output is low for 1800 seconds and then high for 1800 seconds and this continues until /GATE is brought high at which time the "one hour" output returns to the idle state (logic one).

The time base is a 4.096 MHz crystal and thus the accuracy of the clocks is better than 0.01 percent.

Content of the Kit.

The kit consists of a programmed PIC16 in an 18-pin DIP, a 4.096 MHz (HC49U) crystal along with two 20 pFd shunt capacitors and two pull up resistors. A 5V LED is included for testing and a supply of 22AWG solid wire (four colors) is provided for assembly on a solder less breadboard. The kit also includes documentation.


The kit is $6.95.

The kit does not include the source code for the PIC. This may be purchased separately for $25.00. The code was developed using the CCS PCW PIC C compiler. This may be useful if you desire to customize the design to meet your particular requirements.

In developing this I tried to anticipate the clock periods that people would most likely require. If you desire a customized design, the development charge is $25 to $50 depending on the complexity. You can send me e-mail and I will let you know whether I can meet your requirements, the exact development charge and how long it will require for me to develop and verify the design.