The post explains a circuit that will switch off a group of lamps in sequence with a predetermined delay rate, as set by the user through a built in pot. The ideas was requested by Mr. Azam Jamal

 Technical Specifications


I want to make a circuit which works like: I have 9nos 25 watt CFL bulbs and I want that when I switch off the first bulb then after each 5 minutes the remaining light would switch off regularly like each should go off after 5 minutes of other means that in 45 minutes all 9 lights go off respectively.

Please help me ?

The Design


The circuit functioning can be understood as follows:

The first circuit below which is a simple IC 555 and IC 4017 lamp chaser produces the basic sequencing of the lamps at the rate of 5 minutes, the time frequency being determined by the 100k pot setting.

It must be set to produce a frequency that may be 50% of the desired sequencing rate, meaning here it must be set to produce the ON and OFf periods at the rate of 2.5 minutes.

The second circuit is a simple a SCR based relay driver circuit which needs to be repeated 9 times across the intended outputs of the 4017 IC.

As per the request as long as the SPDT is toggled toward the ground position, the IC555 stays disabled and the first lamp(1) is held switched ON indefinitely.

Also in this position, all pinouts of the IC 4017 from pin2 onwards is locked at zero voltage, which means that the connected SCR relay drivers have their relays in their N/C positions making sure that all the connected lamps stay switched ON.

So all the nine lamps from pin2 to pin11 of the IC 4017 is now in an activated position along with lamp1 associated with the SPDT transistor relay driver stage.

At the desired period when the SPDT is toggled, the first lamp(1) is switched OFF and the 555 timer circuit is initiated with its counting process.

After 5 minutes the 555 IC inputs its first legit pulse to pin14 of the 4017 making pin2 to go high which in turn latches the relevant SCR relay driver switching off the first lamp in the sequence.

After another 5 minutes pin4 goes high switching OFF the associated SCR relay driver lamp, and the process repeats until the last pin11 in the sequence gets activated, switching off the last lamp in the sequence, and this also locks pin4 of the IC555 freezing the whole circuit until the operations are reset by the user for restarting the cycle afresh.

Circuit Diagram



The Relay Driver Stage


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