Long Duration Timer Circuit

I was looking for a good timer circuit, one that can produce delays up to several hours. I did have few basic timer circuits that use the 555 IC, but they couldn't be used to effectively get a time delay of few hours because capacitors with low leakage currents are harder to find. So, searched on the internet for alternate solutions.

I found a good circuit at a site named www.brighthub.com. It was a pretty simple circuit but the site claimed it can produce time delays from 60 seconds to maximum of 720 hours! I still haven't tested this out, but I have bought all the parts so I will start constructing it soon. Just thought of sharing the circuit with you in the mean time :)

Here's the circuit

Timer Circuit

The circuit is pretty simple, only two CMOS ICs - 4060 and 4040. The S1 switch is used to select different time configurations and the 50k preset (R1) is used for fine tuning the time delay. The circuit operates on 230v but doesn't use a step-down transformer. This makes the complete circuit very small.

I'll try to briefly describe the functionality of the circuit. 4060 is a 14-Stage Binary Ripple Counter. R1, R2, R3 and C1 makes up a RC Oscillator. The time delay pulses generated by the 4060 (by the pins 1, 2 and 3) are sent to the clock input pin (pin 10) of 4040, which is a 12-Stage Binary Ripple Counter. The delay pulses are divided by 2 in each counter stage of 4040 and a total delay of 2¹⁹ will be obtained at output (pin 1).

You can get the data sheets of 4060 and 4040 from this here
an, you can find the original article here

All credit should go to the original author :)

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