LED Sand Glass Timer Circuit Diagram
This circuit (Fig. 1) simulates the old sand-glass timer. A total of 32 LEDs create the effect of sand grains passing from the upper half of sand-glass to its lower half. When the power is switched ‘on’, shift registers IC3 and IC4 are reset by the power-on-reset circuit formed by resistor R34 and capacitor C7. After a few seconds, the sand-glass action starts. IC CD4060B (IC2) is a 14-stage ripple binary counter with built-inoscillator. It generates clock pulses, which are fed to both the shift registers (IC3 and IC4). The clock frequency can be adjusted by preset VR1, while rotary switch S2 helps in selecting time periods. LED Sand-Glass Timer Circuit Diagram Time period options of 5, 10, and 20 minutes have been provided. Additional options are available on utilising outputs Q3 through Q9 of IC2. Switch S1 is an SPDT switch, which selects odd- or even-numbered set of LEDs. In other words, it selects which side of the sand-glass is up. Assuming S1 to be in position (a), every clock p...