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Description

These two circuits represent multi-range timers capable of periods extending up to 24 hours and beyond. They can be utilized as repeating timers or single-shot timers. Both circuits are fundamentally identical, differing solely in their behavior during single-shot mode. In single-shot mode – when the preset time has elapsed – Version 1 activates the relay, while Version 2 deactivates the relay. Version 1 consumes less power during operation, and Version 2 consumes less power after the timer has ceased. Select the version best suited to your application.

Schematic Diagram No.1

The CMOS 4060 is a 14-bit binary counter. However, only ten of these bits are connected to the output pins. The remaining bits – Q1, Q2, Q3, and Q11 – do exist. You simply cannot access them directly. The 4060 also incorporates two inverters, connected in series across pins 11, 10, and 9. Together with R3, R4, R5, and C3, they form a simple oscillator. While the oscillator is running, the 14-bit counter counts the number of oscillations, and the state of the count is reflected in the output pins. By adjusting R4, you can alter the frequency of the oscillator, thereby controlling the speed at which the count progresses. In other words, you can determine how long it takes for any given output pin to go high. When that pin goes high, it switches the transistor, and the transistor, in turn, operates the relay. In single-shot mode, the output pin also performs a second function. It uses D1 to disable the oscillator, stopping the count when the output pin is high. If you want to utilize the timer in repeating mode, simply omit D1. The count will continue indefinitely, and the output pin will continue to switch the transistor on and off at regular intervals.

Veroboard Layout No.1

Using “Trial and Error” to establish a long time period would be exceptionally tedious. A more efficient approach is to utilize the Setup tables provided and calculate the time required for Pin 7 to go high. The Setup tables on both schematics are interchangeable; they are simply two distinct ways of expressing the same equation. For example, if you desire a period of 9 Hours, the Range table indicates that you can employ the output at Pin 2. Pin 2 needs to go high after 9 x 60 x 60 = 32 400 seconds. The Setup table tells you to divide this by 512, yielding approximately 63 seconds. Adjust R4 so that the Yellow LED illuminates 63 seconds after power is applied. This will result in an output at Pin 2 after approximately 9 Hours.

IMPORTANT

Do not utilize the “on-board” relay to switch mains voltage. The board’s layout does not provide sufficient isolation between the relay contacts and the low-voltage components. If you require to switch mains voltage, mount a suitably rated relay somewhere safe – Away From The Board.

Schematic Diagram No.2

Ideally, C3 should be non-polarized; however, a standard electrolytic capacitor will function effectively, provided it doesn't leak excessively in the reverse direction. Alternatively, you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors back to back, as shown. If you need a longer period than 24 hours, increase the value of C3. The reset button is optional; however, it should NOT be used during setup. The time it takes for the Yellow LED to light MUST be measured from the moment power is applied. Although R1, R2, and the two LEDs assist with the setup, they are not necessary for the operation of the timer. If you wish to reduce power consumption, disconnect them once you have completed the setup. The timers were designed for a 12-volt supply; however, provided a suitable relay is utilized, both circuits will operate at anything from 5 to 15 volts. Applying power starts the timer, and it can be reset at any time by a brief interruption of the power supply. The Support Material for this circuit includes a step-by-step guide to the construction of the circuit-board, a parts list, a detailed circuit description, and more.

Veroboard Layout No.2