I'm planning to use barrels full of water to make a drip watering system. I can make the water controls from a pretty easy toilet fill&flush valves and balance it so it needs a very light push on the vertical axis to open/shut.

I need the plants to be watered at night only. Not strictly so it can spill a bit into the morning. So basically it has to be at one position during the day and another during the night.

I'm not an English native and my tech terminology is lacking, so I don't really know what to ask google to find me.

I don't know if light detection or a timer on it would be cheaper.

Failing electronics I guess I can make something with a parabolic mirror or Fresnel lens a metal plate feeding into a sterling engine.

  • $\begingroup$ Why not rotate cams to open / close? Or ball valves? $\endgroup$
    – Solar Mike
    May 17, 2022 at 5:22
  • $\begingroup$ The garden water time suggested by @vladimir is a simple & practical solution, but it does require electrical energy, for which a solar powered battery might suit. If you only want to consider mechanical energy you may have to adapt something like the old fashioned wind-up alarm clocks. $\endgroup$
    – Fred
    Jun 18, 2022 at 23:30

2 Answers 2


Most easy way is to buy inexpensive garden water timer. Simplest one contains ball valve with motor, two dials for setting watering period and time and is powered by two 1,5 V cells.

If you wish non-electronic autonomous solution, then consider pneumatic or hydraulic system, coupled to ball valve, or typical screw valve with screw removed. It can be constructed from usual water pipes filled with mineral oil. Pipes volume and thus, length, is calculated from temperature difference in your area (or greenhouse). As actuator you can use pneumatic cylinder, they are common in cars and various furniture, depends of machining equipment, you have access to.


Rather than answer your open-ended question, consider to search for " Arduino light dependent resistor" along with "Arduino," "servo control for Arduino."

You should be able to find links for controlling servo motors with an Arduino, also to use the light dependent resistor to measure the light levels.

The foundation may be something along the lines of:

Is light level low enough to activate servo to release water? Yes. - trigger servo No. - don't trigger servo

From the first link, code is pre-written to check the light level and illuminate an LED to indicate dark - LED on, not-dark, LED off. Combining the code with the servo actuation may be all that you need.

  • $\begingroup$ Yeah, it got me started pretty well. I'll dig for parts for a bit, see if its cost effective versus a prefab battery timer. Oh and you can also fiddle with a greedy cup balancing act if you ever wanna try to skip all the electronics. $\endgroup$ May 16, 2022 at 23:36

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