Programmable digital clock for watering flower pot

Thread Starter

Peter8519

Joined Nov 18, 2014
35
Hi All,
I am thinking of setting a simple circuit to water my potted plants e.g. at 7am and 7pm.
I need the following.
1. Simple circuit powered by 6-9V battery to turn on either a DC motor or a DC normally closed valve.
2. Preferably an off the shelve parts.

Thanks in advance.

Special thanks to blocco a spiral for the water level sensing circuit. After 2 years, it still working and still using the same 9V battery.
 

shteii01

Joined Feb 19, 2010
4,644
1. some kind of Real Time Clock (RTC) module that talks to Uno (preferably with tutorial on how to use it, Adafruit has one so you should be able to find similar one on Ebay and use Adafruit tutorial)
2. Chinese Uno from Ebay (you can also try Chinese Nano)
3. Chinese dc motor shield for Uno from Ebay (preferably with tutorial on how to use it)
 

Thread Starter

Peter8519

Joined Nov 18, 2014
35
@shteii01,
I would avoid UNO route as it needs programming. After some research online, I think I am leaning towards digital timer switch. Unfortunately, it's most 12V DC. I am looking for a 3-6V DC digital timer switch because I will put this device outdoor. I just need to program it to turn on at 7am for 20-30 seconds everyday. Next I need to decide whether to use a normally close valve or a submersible water pump. I will use gravity feed if I choose valve option. Which is more power efficient ?

@crutschow,
I will use a plastic water container and I will top up the water once a week. I am a lazy gardener. :)
 

shteii01

Joined Feb 19, 2010
4,644
@shteii01,
I would avoid UNO route as it needs programming. After some research online, I think I am leaning towards digital timer switch. Unfortunately, it's most 12V DC. I am looking for a 3-6V DC digital timer switch because I will put this device outdoor. I just need to program it to turn on at 7am for 20-30 seconds everyday.
ironic that you keep using word programming.
 

LesJones

Joined Jan 8, 2017
4,171
I have found that most of the mains plug in timers I have seen use a timer module that runs on about 1.2 volts from a single Ni-Mh cell that is charged when plugged into the mains. This module gives a small output signal that drives a couple of transistors to drive a relay on the power board. You could use the timer module to drive a couple of transistors that would drive the 3 volt pump. The cell in the timer part could be charged via a resistor and diode from the 3 volts power supply.
Edit. I've just realised you only want 20 to 30 seconds. All the digital timers I have seen have a minimum on time of one minute so you would also need a 555 or similar to get the shorter ON time.

Les.
 

kubeek

Joined Sep 20, 2005
5,793
Also beware that if the timer fails after it turns the water on, you might have a lot of water in places where it should not be.
Same goes for other things like heaters, friends arduino code somehow got stuck and all his chilli peppers got very dry and very dead in his little desktop greenhouse.
 

Thread Starter

Peter8519

Joined Nov 18, 2014
35
I have found that most of the mains plug in timers I have seen use a timer module that runs on about 1.2 volts from a single Ni-Mh cell that is charged when plugged into the mains. This module gives a small output signal that drives a couple of transistors to drive a relay on the power board. You could use the timer module to drive a couple of transistors that would drive the 3 volt pump. The cell in the timer part could be charged via a resistor and diode from the 3 volts power supply.
Edit. I've just realised you only want 20 to 30 seconds. All the digital timers I have seen have a minimum on time of one minute so you would also need a 555 or similar to get the shorter ON time.

Les.
555 is difficult route to take. :(
 

Thread Starter

Peter8519

Joined Nov 18, 2014
35
Also beware that if the timer fails after it turns the water on, you might have a lot of water in places where it should not be.
Same goes for other things like heaters, friends arduino code somehow got stuck and all his chilli peppers got very dry and very dead in his little desktop greenhouse.
My wife told... don't make it too complicated. Just water the plant once a day.
Or use this...
https://i.ebayimg.com/images/g/jkQAAOSwSgJXOT~X/s-l1600.jpg
 

ebeowulf17

Joined Aug 12, 2014
3,307
Also beware that if the timer fails after it turns the water on, you might have a lot of water in places where it should not be.
Same goes for other things like heaters, friends arduino code somehow got stuck and all his chilli peppers got very dry and very dead in his little desktop greenhouse.
The thread starter will at least have limited damage in such a case, since the plan is to work from a water bottle, not a plumbed water source.

I recently discovered the joy of watchdog timers on an industrial-ish fan control project using an Adafruit Feather M0 (Arduino Zero equivalent.) The board was crashing and hanging somewhat regularly, but I found a helpful library and learned how to use the watchdog function in the M0 to restart the system anytime it got stuck.

The watchdog was a lifesaver until we were able to find the source of electrical noise that was causing the crashes, and managed to solve the problem with improved grounding practices.
 
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