repeating interval timer

This circuit features an adjustable output timer that can re-trigger at regular intervals. The output duration can range from a fraction of a second to over half an hour, with the ability to recur at intervals from seconds to days. The output section utilizes a simple Monostable Circuit. When Pin 6 of the CMOS 4001 is activated, the monostable triggers and the relay energizes, remaining energized for a duration determined by C1 and R3. With the specified values, R3 allows for 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 of 3 to 5 seconds. Due to manufacturing tolerances, the exact duration of the output period depends on the characteristics of the components used. The CMOS 4060 functions as a 14-bit binary counter equipped with a built-in oscillator. This oscillator comprises two inverters connected to Pins 9, 10, and 11, with its frequency regulated by R7. The oscillator output is internally linked to the binary counter, which counts the oscillations while the oscillator operates, reflecting the count state on the output pins. By adjusting R7, the time for any specific output pin to go high can be set. Connecting that output to Pin 6 of the CMOS 4001 will trigger the monostable each time it goes high. Ideally, C4 should be non-polarized; however, a standard electrolytic capacitor may suffice if it does not leak excessively in reverse. Alternatively, two 22 µF capacitors can be connected back to back to simulate a non-polarized 10 µF capacitor. It is advised not to use the onboard relay to switch mains voltage due to insufficient isolation between relay contacts and low-voltage components. For mains voltage switching, a suitably rated relay should be mounted away from the board. A single-pole changeover (SPCO/SPDT) relay is used, though a multi-pole relay can also be employed. Given the potential for long delays between outputs, utilizing a Setup Table for time calculations is recommended to avoid tedious trial and error. For example, to trigger the monostable every six hours, the time for Pin 1 of the CMOS 4060 to go high must be calculated. Pin 1 should go high every 21,600 seconds (6 hours), and according to the Setup Table, this figure should be divided by 512, resulting in approximately 42 seconds. Adjust R7 to ensure the Yellow LED illuminates 42 seconds after power is applied, causing Pin 1 to go high after three hours and to remain high for that duration before toggling low for another three hours. This cycle repeats every six hours, with the relay energizing after the initial three-hour delay. The reset button should not be engaged during setup, as the timing for Pin 7 to go high and the Yellow LED to illuminate must be measured from the moment power is applied. Although components R4, R5, and the two LEDs assist with setup, they are not essential for timer operation and can be disconnected to reduce power consumption. The timer is designed for a 12-volt supply but can operate within a range of 5 to 15 volts, provided a suitable relay is utilized. Powering the circuit 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, increasing the value of C4 is recommended.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 i s 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.

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 wish. 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. 🔗 External reference