Saturday, December 20, 2008

Frequency Divider

I am always looking for perfect frequency oscillator for a given budget for my clock projects. Searching on eBay provided a lot of good frequency oscillators including OCXO (Oven Controlled Crystal Oscillator) and Rubidium Frequency Oscillator. Most of them are for telecommunication systems and audio systems. But, I want to use the oscillator just for making a good clock. Yes, just a real clock for telling time.Those oscillators on eBay provide frequencies that not suitable for making a clock. For example, 10MHz,11.2896, MHz, 16.9344MHz etc.,

There are some techniques to make use of these oscillators in clock projects. I have post a solution for 11.2896MHz in "Using 11.2896 MHz with TMR1 (timer1 module)".

For 10MHz oscillator, I will use ripple counters as the frequency divider to divide the 10MHz to lower frequency and use it as a time reference for my clocks. I got information about 10MHz frequency division from Seiichi Inoue's website. From the web, 10MHz frequency can be divided by using 3 pcs. of Dual Decade Counter (74390 or 74HC390). By using the schematic below, I can get 100Hz from 10MHz input. By feeding 100Hz to PIC Microcontroller with appropriate firmware I will get a good accuracy clock.
10MHz Frequency DividerIt's not so easy to divide 16.9344MHz to appropriate frequency for my clocks. However, I will try to figure it out and post it here.

1 comment:

Stefan said...

This is very interesting. But how can you divide a frequency just using the pic. let s say divide a 10 Mhz crystal frequency to 1Mhz or100 khz?