Here is one basic circuit of a simple but accurate 1Hz timebase generator built around a standard Quartz clock circuit board. Just lift the clock PCB from any cheap quartz clock and carefully remove all extra components like the drive coil, buzzer, alarm switch and clock mechanism (quartz movement), etc.
Next wire the circuit as shown in the schematic diagram, observing correct connection points and polarities, and power it from a 5VDC supply. Precision 1Hz clock signal generator is now ready to serve you. With suitable modification(s) at the output you can use this circuit to drive blinkers, beepers and microcontroller based ciruits.
- 1. Stable 1.5-1.6 VDC supply for the clock PCB is derived from the 5VDC input supply with the help of componets R1, D1 and C1. Only use a 10mm Red color (Vf=1.6V) LED for D3.
- 2. Drive coil outputs (L1&L2) of the clock PCB are joined together to get one second pulse output with the help of two schottky diodes (D1&D2). Such low-drop diodes are crucial for this circuit.
- 3. The circuit is inverting output type and hence, the output is normally at high level,and pulses low once a second.By adding a second (optional) transistor, this can be reversed, ie non inverting, so that the output is normally at low level, and pulses high once a second.