Description:
These two circuits are versatile 24 Hour Timer capable of providing timing intervals exceeding 24 hours. They share a fundamental design but diverge in their relay operation: Version 1 energizes the relay when the timer expires, while Version 2 de-energizes it. The first variant consumes less power while the timer is active, while the second conserves power once the timer concludes. Choose the one that aligns best with your specific application.
Notes:
The CMOS 4060 is a 14-bit binary counter that comes equipped with an integrated oscillator. This oscillator is composed of two inverters connected to Pins 9, 10, and 11, with its frequency determined by the values of R3, R4, and C3. While the oscillator is in operation, the green LED flashes, and the IC keeps track of the oscillation count. It’s worth noting that even though it’s a 14-bit counter, not all of the bits are accessible, and the ones that can be accessed are indicated in the diagram.
By adjusting the oscillator’s frequency, you can set the duration required for a specific output to go high. This output then triggers the transistor, which subsequently activates the relay. Simultaneously, D1 halts the counting process by disabling the oscillator.
Ideally, C3 should be a non-polarized capacitor, but a standard electrolytic capacitor can suffice as long as it doesn’t exhibit excessive leakage in the reverse direction. Alternatively, you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors in a back-to-back configuration, as depicted.
Setting a lengthy time period through a trial-and-error approach would be quite laborious. A more efficient solution is to utilize the provided Setup tables and calculate the required time for Pin 7 to go high. These Setup tables are interchangeable between both schematics, representing different ways of expressing the same equation.
For instance, if you desire a 9-hour period, consulting the Range table reveals that you can utilize the output at Pin 2. To achieve a high output at Pin 2 after 9 x 60 x 60 seconds (which equals 32,400 seconds), refer to the Setup table, which advises dividing this by 512, yielding approximately 63 seconds. Adjust R4 accordingly so that the yellow LED illuminates after 63 seconds from power application. This configuration will result in an output at Pin 2 after approximately 9 hours.
Support material for these timers includes comprehensive circuit descriptions, parts lists, a step-by-step construction guide, and more. Additionally, you’ll find suitable Veroboard layouts for each version below.
The timer was originally designed for a 12-volt power source. However, by utilizing an appropriate relay, the circuit can function within a voltage range spanning from 5 to 15 volts. Applying power initiates the timer, and it can be reset at any point by briefly interrupting the power supply. While the reset button is an optional component, it is important not to employ it during the setup phase. To accurately measure the time it takes for the Yellow LED to illuminate, it must be timed from the instant power is applied.
It’s worth noting that R1, R2, and the two LEDs serve to assist in the setup process but are not essential to the timer’s operation. To decrease power consumption, these components can be disconnected once the setup is completed. If a time period exceeding 24 hours is needed, you can achieve this by increasing the value of C3.
