In this post we learn about an automatic programmable 7 day plant watering system circuit as requested by Mr. Michael.
Here's the requested as given in the below paragraph
Hello admin,
The timing circuit must be powered with 9v and its function will be to switch on and off a 9v supply to a microcontroller circuit at programmed intervals once every one, two, three ….. up to seven days through a trimpot marked 1-7.
The circuit must switch off after 20 secs.
The time delay of the first (and subsequent) switch-ons should also be programmed through a trimpot marked 1-12 (hours) and a “SET” button.
The whole philosophy is the same with some automatic watering programmers (no screen or real time needed).
Thanks, Michael
The automatic plant watering timer circuit can be visualized in the above images. The description can be understood from the following explanation:
1) IC 4060 is wired as a standard timer circuit which generates clock signals at a rate depending on values of the R, C components connected across its pin#9 and pin#10. This could be set to achieve a clicks signals with delays of 1 hour, 2 hour or whatever may be required to appear at pin#3 of the IC. Only one of the 7 stages are shown above, for 7 days week you will have to make 7 nos of IC 4017 stage...the 4060 need not be repeated, the signal from pin#3 and BC557 of IC 4060 can be commonly applied to all the 4017 stages.
3) THe above clocks are transferred to pin#14 of IC 4017 via the BC557 transistor.
4) Te IC4017 responds to each positive edged clocks and shifts a logic high across its pin#3 to pin#8
5) The selector switch across the 4017 outputs decides after how many hours the next similar stage needs to be triggered so that the next 4017 stage repeats the timing cycle, and subsequently the next second 4017 stage triggers the 3rd 4017 stage through its own selector switch and the BC547 stage....and so on.
The 20 second Delay Timer circuit for the programmable plant watering timer circuit
Pin#2 of the IC 4017 can be connected to a 20 second delay OFF timer circuit, which can be built as per the below given diagram. Pin#2 of the 4017 IC is configured with the 33uF end of the following circuit.
When power is first switched ON, the IC 4017 and 4060 both get reset, and simultaneously the logic from pin#3 of 4017 jumps to its pin#2.
This initiates the 20 second timer circuit by triggering its relay ON.
The relay now powers the MCU...but only until 20 seconds have elapsed, when the timer switches OFF the relay ans the MCU.
After this the IC 4060 keeps counting and with every logic high clock it forces the IC 4017 to shift its logic across the shown output pinouts.
Depending on which pinout is connected with the selector switch the 4017 C latches and halts when the logic shifts on that particular pinout.
Once this happens , the BC547 carries forward the process and triggers the next 4017 IC, and the same process is repeated with the second stage until the 3rd stages is trigger and s on.
Modified water timer diagram as per the rectifications suggested by Mr. Michael:
Please refer to the comment discussion for the details.
Michael Lomvardeas says
Hello admin,
What do you think the time accuracy of the main system would be (minutes per month)?
If I incorporated another 4060 timer for the 0-12 hour initial delay how could it be deenergized after the initial setup. Otherwise would it not keep sending signals every so many hours to the main circuit?
Michael
admin says
Hello Michael,
The accuracy will depend on the timing capacitor quality, it could be anywhere from 1 minute to 5 minutes per month.
the 0-12V timer will be a one-shot timer, it will initiate the above timer network and latch-up in that position permanently until power is switched OFF
Michael Lomvardeas says
OK admin,
So for 1 hour intervals that we need we have;
22/R = 54/3600
R= 1467 or 1.47M
and so we have an initial delay timer for 1-10 hours.
OK.
What about the repeating every 1-7 days of the watering?
How do we deal with this??
Regards, Michael
admin says
No, it has to be 2.4 hours setting for 4060, this will allow the 4017 outputs to cycle at 24 hour rate, and this will switch ON the water controller exactly on the same hour on which it was initiated on the first day.
suppose you initiate the system at 10 o clock on day 1, this will go erpeating at 10 o clcock everyday infinitely until te system is reset for a new time.
admin says
If you think that the 0-12 hour is important then you can incorporate another 4060 timer, which can be used to first initiate the above design at the desired hour, once initiated the above circuit would then go on repeating the water controller switching each day at the preferred hour
Michael Lomvardeas says
Hello again,
Can you please give me an example setup?
We have two controls over the system; one 1M trimpot on 10 of IC 4060 and a switch 1-9 on IC 4017.
Suppose we want the first watering to start in, say, 6 hours from now and we want it to repeat once every 3 days at the same time.
What exactly do we do?
admin says
Hello, since this circuit is very simple and basic it might not allow the user to get a specific desired delay during the initial set up.
the 4060 will need to be adjusted to get 2.4 hours delays at pin#3, the 4017 will respond to these delays and will move one step across its outputs after every 2.4 hours, that means the initial set up will need to be with multiples of 2.4 hours, meaning if it’s 11 clock now, you get the first option after 2.4 hours that is 1:24, and so on. This 1:24 example will correspond to pin#4 of 4017 (pin#1 of the switch), and the switch will need to be shifted at this point…therefore each interval will be achieved after 2.4 hours…remember here 0.4 does not mean 40 minutes rather this must be multiplied by 60 to get minutes….
How to set up the 4060 IC.
Remove the pot we don’t need it, replace it with a short.
so now we have only the 100K in place. Replace it with 22k to make things quicker.
isolate the pin#3 of the 4060 from the BC557, and connect an LED from pin#3 to ground through a 1K resistor.\
switch on the supply and check after how many seconds/minutes the LED lights up.
Note it down. suppose you find it to be 54 seconds
Now we have the following data with us
22K resistor, 54 seconds, 2.4 hours (required delay)
the reistor in place of the 22Kresistor with resepct to 2.4 hours can be found through this simple cross multiplication
22/R = 54/2.4 (convert in seconds)
22/R = 54/7200
R = 22 x 7200/54 = 2933K or 2.9 meg
so finally the place the 100K is shown can be replaced with a fixed 2.9M to get 2.4 hour delay at pin#3 of 4060.
the above is just an example and the real value can be found only after a practical calculation
Michael Lomvardeas says
Great, thanks
I will test it in practice and let you know.
Regards Michael
admin says
you are welcome!!
Michael Lomvardeas says
Hello,
If it’s not too much trouble, whenever you have the time, could you please show me the final circuit?
As I said I am practically ignorant at electronics and I’m afraid i will make a mess of things.
Much olbliged,
Michael
admin says
Hello, I have updated the modified diagram in the post.
Michael Lomvardeas says
Hello and thank you for the circuit.
Can you please clarify a couple of things for me?
The initial time delay of 1-12 hours should function only once which is during the initial setup. For example if we set up the timer at 5 pm and we want it to switch on for the first time at 3am we give it a delay of 10 hours. After this the time delay function should not interfere at all.
Is this what your circuit does?
Also wat do you mean by “for 7 days week you will have to make 7 nos of IC 4017 stage”? What does this mean in practice?
Thanks a lot, Michael
admin says
Hello, I thought that the 1-12 hour adjustment was required for all the days of the week…if not then the circuit become even more simple and the 7nos of separate 4017 IC stages will now not be required.
The circuit which is shown above now can be directly applied for the application.
The rotary switch can eb used for setting up the switch ON time for each day.
Please note that if the 4060 pin#3 ON + OFF delay is set for 1 hour then the output of the 4017 I will shift with a delay of 1 hour….if it’s set for 2 hours then it will shift at the rate of 2 hours. since we have 10 outputs for the 4017 IC, we can set the 4060 timing at 2.4 hours, which will enable the end to end cycle of the 4017 outputs to complete at every 24 hours.
Modification:
The only modification that is required now in the circuit is to eliminate the entire BC547 stage along with its base 100K and collector 1M resistor.
also, now the selector switch’s output connects with the 20 second delay timer and not the pin#2 of 4017.
admin says
couple of more modifications are required as given below:
the 0.47uF connected with pin#15 of 4017 can be removed, and this pin must be now connected with pin#12 of IC 4060.
1N4148 and 1M associated with pin#13 of 4017 can be removed and pin#13 can be directly connected with ground