Crystal Controlled Timebase Circuit Diagram

Crystal Controlled Timebase Circuit Diagram

Crystal Controlled Timebase

This circuit provides a 50 Hz timebase signal that is independent from the power line frequency. It is designed to provide the 50 Hz signal for electronic circuits which function only with this clock frequency (mostly circuits and electronic devices with european standards). 

It is popularly used for clock and timing applications. By carefully analysing the circuit diagram, you can see that IC1 works as crystal controlled oscillator while IC2 functions as a 214 divider. 

The crystal frequency can be finely adjusted within 20 Hz range through the trimmer capacitor C2. Calibration is simple and can be done in two different ways. 

First method: if you have a digital frequency counter, connect it to pin 7 of IC1 (TEST output on the printed circuit board) and adjust trimmer cap C2 until the frequency being displayed is 204.800 Hz.

Now, if you don't have a frequency counter; just set the trimmer capacitor C2 at its middle position. This calibration method is of course not the most accurate but will be sufficient for most applications.

The output frequency, in this case, has a very negligible error of around 0.12 ppm. This timebase source delivers three frequencies: 50Hz, 100Hz, and 200Hz. 

Now, if you want to divide further the output signal to obtain much lower frequencies, you can cascade additional 4013 flip-flop IC's at the output. Each 4013 has two integrated flip-flops.

You can power this circuit with voltages ranging from 5 volts up to 15 volts. This very wide power supply range is possible through the use of CMOS type ICs. 

The current consumption is very low - a typical character of a CMOS - between 0.4 and 3 mA.

Printed Circuit Crystal Controlled Timebase


Parts Placement Layout Crystal Controlled Timebase


External Wiring Layout Crystal Controlled Timebase


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