Repeating Interval Timers

Do not use the on-board relay to switch mains voltage. The board's layout does not provide adequate isolation between the relay contacts and the low-voltage components. If mains voltage switching is required, mount a suitably rated relay in a safe location away from the board. A SPCO/SPDT relay has been used, but a multi-pole relay may also be suitable. This circuit features an adjustable output timer that can re-trigger at regular intervals. The output period can range from a fraction of a second to over half an hour, with recurring intervals from seconds to days. The output section utilizes a simple monostable circuit. When Pin 6 of the CMOS 4001 is taken high, the monostable triggers, energizing the relay for a duration determined by components C1 and R3. With the specified values, R3 allows output periods of up to approximately 30 minutes. However, component values can be adjusted to meet specific requirements. For instance, reducing R3 to 1 MΩ and C1 to 4.7 µF will yield maximum output periods between 3 and 5 seconds. Due to manufacturing tolerances, the exact timing will depend on the characteristics of the components used. The CMOS 4060 is a 14-bit binary counter with an integrated oscillator, which consists of two inverters connected to Pins 9, 10, and 11. The frequency of the oscillator is controlled by R7, and its output is linked to the binary counter. While the oscillator operates, the IC counts oscillations, and the count state is reflected at the output pins. By adjusting R7, the time for any output pin to go high can be set. This output is connected to Pin 6 of the CMOS 4001, triggering the monostable each time it goes high. Ideally, C4 should be non-polarized, but a standard electrolytic capacitor can be used if it does not leak significantly in the reverse direction. Alternatively, a non-polarized 10 µF capacitor can be simulated by connecting two 22 µF capacitors back-to-back. Given that output delays can extend for hours or days, a trial-and-error approach for timer setup would be inefficient. A more effective method is to utilize the provided setup table to calculate the time required for Pin 7 of the CMOS 4060 to go high. For instance, to trigger the monostable every six hours, the range table indicates using Pin 1 of the CMOS 4060. Pin 1 needs to go high every 21,600 seconds (6 hours). The setup table suggests dividing this figure by 512, resulting in approximately 42 seconds. Adjust R7 so that the yellow LED lights up 42 seconds after power is applied, causing Pin 1 to go high after about three hours. Pin 1 stays high for three hours before going low for another three hours, repeating this cycle. Consequently, after an initial delay of three hours, the relay will energize and subsequently re-energize every six hours. The reset button should not be utilized during setup. The timing for Pin 7 to go high and the yellow LED to illuminate must be measured from the moment power is applied. Although R4, R5, and the two LEDs assist with setup, they are not essential for timer operation. To reduce power consumption, these components can be disconnected after setup is complete. The timer is designed for a 12-volt supply but can function within a range of 5 to 15 volts, provided a suitable relay is employed. Power application initiates the timer, which can be reset at any time by briefly interrupting the power supply, making a reset button unnecessary. For delays exceeding 32 hours, the value of C4 should be increased.

This circuit design incorporates a CMOS 4001 monostable multivibrator and a CMOS 4060 binary counter to create a versatile timer system capable of controlling a relay for various applications. The monostable circuit is triggered by a high signal on Pin 6 of the CMOS 4001, which is activated by the output of the oscillator in the CMOS 4060. The timing of the relay activation is determined by the RC time constant of the components connected to the monostable. The circuit's flexibility allows for adjustments in timing intervals by varying resistor and capacitor values, making it adaptable for different operational needs.

The use of a relay for switching mains voltage is cautioned against due to inadequate isolation on the board. Instead, a separate relay should be used in a safe location. The design can accommodate various relay types, depending on the application requirements. This timer circuit is particularly useful in automation and control systems where precise timing and reliability are essential. The ability to set long delays and recurring intervals makes it suitable for applications such as irrigation systems, lighting control, and other timed operations. The circuit's low power consumption and adaptability to different voltage levels enhance its usability across a range of electronic projects.Do not use the "on-board" relay to switch mains voltage. The board`s layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe - Away From The Board.

I`ve used a SPCO/SPDT relay - but you can use a multi-pole relay if you w ish. This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days and beyond. The output section is a simple Monostable Circuit. When Pin 6 of the Cmos 4001 is taken high - the monostable triggers - and the relay energizes. It will remain energized for a period of time set by C1 & R3. With the values shown - R3 will provide output periods of up to about 30-minutes. However, you can choose component values to suit your requirements. For example, if you reduce R3 to 1meg - and C1 to 4. 7uF - the maximum output period is between 3 and 5 seconds. Owing to manufacturing tolerances - the precise length of the time period available depend on the characteristics of the actual components you`ve used.

The Cmos 4060 is a 14-bit binary counter with a built-in oscillator. The oscillator consists of the two inverters connected to Pins 9, 10 & 11 - and its frequency is controlled by R7. The output from the oscillator is connected internally to the binary counter. While the oscillator is running - the IC counts the number of oscillations - and the state of the count is reflected in the output pins.

By adjusting R7 - you can set the length of time it takes for any given output pin to go high. Connect that output to Pin 6 of the Cmos 4001 and - every time it goes high - it`ll trigger the monostable. Ideally C4 should be non-polarized - but a regular electrolytic will work - provided it doesn`t leak too badly in the reverse direction.

Alternatively - you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors back to back - as shown. Since the delays between outputs can last for hours - or even days - using "Trial and Error" to set-up the timer would be very tedious.

A better solution is to use the Setup Table provided - and calculate the time required for Pin 7 of the Cmos 4060 to go high. For example, if you want the monostable to trigger every Six Hours - the Range Table tells you to use Pin 1 of the Cmos 4060.

You need Pin 1 to go high every 6 x 60 x 60 = 21 600 seconds. The Setup table tells you that for Pin 1 you should divide this figure by 512 - giving about 42 seconds. Adjust R7 so that the Yellow LED lights 42 seconds after power is applied. This will cause Pin 1 to go high after about 3 Hours. When Pin 1 goes high it will stay high for three hours. It will then go low for three hours - before going high once again. Thus, Pin 1 goes high once every six hours. It`s the act of going high that triggers the monostable. So - after an initial delay of three hours - the relay will energize. It will then re-energize every six hours thereafter. The reset button should NOT be used during setup. The time it takes for Pin 7 to go high - and the Yellow LED to light - MUST be measured from the moment power is applied.

Although R4, R5 and the two LEDs help with the setup - they are not necessary to the operation of the timer. If you want to reduce the power consumption - disconnect them once you`ve completed the setup. The timer is designed for a 12-volt supply. However - provided a suitable relay is used - it will work at anything from 5 to 15-volts. Applying power starts the timer. It can be reset at any time by a brief interruption of the power supply - so a reset button is not strictly necessary.

If you need delays in excess of 32-hours - increase the value of C4. The Support Material for this circuit includes a step-by-step gu 🔗 External reference