Thursday, March 26, 2015

Making a Flexible Programmable Timer Circuit

This circuit of a flexible programmable timer circuit explained in this article was designed by me in response to a request by Mr.Amit. Lets know more about the request and the circuit details.

"i need a circuit for my auquarium where it should do the following

it should switch off the lights at 10:00 pm and start at 7:00 am daily + switch off the light at 12:00 pm daily and switch up at 6:00 pm back.

this will help to make my fishes live longer. :)

Thanks in advance.

Amit desai"

So heres the circuit that I came up with. As the name suggest, the timeer is pretty flexible and may be adjusted to produce any desired time periods, according to the above requested format.

The circuit consists of four identical stages, made up of the IC 4060 timer configuration. Te timer sequence begins from the IC at the top left corner.
When power is switched ON this IC starts counting. Depending upon the setting of its pot, the IC triggers after a certain period og time interval.
This switches ON the relay and the driver transistor BC547 which consequently switches OFF the connected lamp. The stage gets latched with the help of the diode connected across its pin 3 and pin 11.
The above triggering  also switches another BC547 transistor which connects the reset pin of the next IC 4060 to ground which initiates this stage also. After a predetermined time, this IC also triggers its output at pin3 and gets latched by the corresponding diode, however this actionsends a feedback signal to the relay driver transistor, instantly switching it off and restoring power back to the lamp so that it lights up again.
Just as the above actions, the sequence further proceeds and switches ON the third IC 4060 in the line which counts the set time interval and pulls the relay back to OFF position via the diode connected to the collector of its bc547 transistor, such that the lamp again gets switched OFF.
As soon as the above triggering happens the last section at the bottom right corner switches into action and counts as per the setting of the respective pot, until the ICs output becomes high, this high reset the the first IC and switches ON the lamp once again so that the process may be restart the cycle all over again.

The pots may be increased to 3m3 for generating higher time interval periods, so is true with the respective capacitors.

The timer may be adjusted as per the sent request, in the following manner:

If we consider the first timing sequence to begin at 7am and end at 12pm, means the upper left timers P1 needs to be adjusted such that it activates the relay and switches off the relay after exactly 5 hours.

For keeping the lamp switched OFF in the above position and switch it ON back at 6 pm we now adjust P1 of the upper right timer section such that its output triggers after another 5 hours. This switches ON the lamp again.

The above situation needs to be kept intact until night 10pm, which is about 4 hours of period, therefore we adjust the lower right timers P1 to get it triggered after 4 hours of time interval.

Finally, for initiating the above procedure back again the next morning at 7am, P1 of the last timer at the lower right is adjusted such that it resets the first timer after 9 hours..... and the cycle repeats.

For making the circuit work according to the above specified timing pattern, after adjusting the respective hours, the unit should be powered or switched ON exactly at 7 clock in the will automatically follow.

No comments:

Post a Comment