Introduction: Automated Bonsai Watering (without Arduino)

About: Hello - I am the scientist formerly known as Naegeli and of course I was inspired by the artist formerly known as Prince. But in contrast to his royal badness I do not want be become the king of pop but the ki…

This Instructable shows you how to make an automated watering system for Bonsai trees or plants (see video) yourself. In contrast to a lot of systems that you can buy, this system does not need a water-connection. The water is pumped from a small tank to make it ideal for indoor use of small plants. The system is using standard industrial items like a digital timer switch where no programming or coding is needed (without Arduino). Main components are the following:

  • Timer (Digital weekly programmable time switch)
  • Peristaltic pump
  • DC to DC step down converter
  • Power adapter

In addition, this Instructable shows you how to construct a fast and easy to build but nice-looking housing. The method described here is using cardboard in combination with “preglued edging strips” as the main construction material (like an exoskeleton of an insect). In this way a rigid housing is formed within minutes that is splash water proof. The preglued edging strips can easily be attached to the cardboard surface by the use of an iron and offers unique machining properties with household tools. The smooth surface is grindable and it can be cut with scissors or craft knives. The combination allows for a fast prototyping (“rien ne dure que le provisoire” as the French says). I prefer this method since during daily use often you realize that another construction design would be required. Therefore, I usually do not want to invest much time into the housing. In the bad case of a redesign you can easily take the enforced cardboard apart and re-use your equipment.

One downside of the timer is that the minimal programmable time is only one minute e.g. 17:45 – 17:46. One minute with a fast running pump can already deliver more water than a small bonsai pot can absorb. The possibilities you have to adjust the amount of water beside the duration is the rotation speed of the pump. This can be regulated by adjusting the voltage with the step-down converter. An additional possibility that is shown here is to adjust the amount of water with a special drip irrigation system that allows for regulation. I found that socket-terminal strip allows for an easy way to adjust the water flow to a few drops per second.

Step 1: Design

So, the principle of this watering system is not to use a conductivity measurement to start watering but just a fixed time interval. Time dependent intervals with Arduino are not that easy because you need to have an own clock module like a DS3231 element, a keypad to enter data and of course a display. Furthermore, you need to make all the coding and in the case of power failure you lose all your variable settings. Therefore, an ideal solution is an industrial timer which has its own built-in back up battery. It includes a display and the keypad for data entry. On top this unit comes with a prize in the range of 6 US $ and therefore sounded interesting. Don’t get me wrong – I love Arduinos but since my coding skills are limited I thought that this way would lead to a faster project end.

The prototype of this setup here is successfully running for two years now. The peristaltic pump is in operation daily for one minute. The tank has enough volume for 2 month when a one minute watering time is used per day. There is no need any more to ask your neighbor or your kids to water your plant when you are abroad (smile).

Step 2: Parts List

Timer (LCD Digital Power Programmable Timer AC 12V 16A 4.4VA Time Relay Switch, Aliexpress 6.32US $): The chosen timer switch has to be operated with 12 volts. I would have preferred a timer switch with a lower voltage requirement to use batteries for a stand-alone version but at that time I could not find anything running on 6 volts (maybe due to the relay inside). The timer offers all features that you ever need like different intervals (every day, every second day etc.) and duration. The timer offers also a manual ON/OFF switch in case you want to test your set-up (calibration).

Peristaltic pump (6V Dosing peristaltic pump, AliExpress 13.82 US $): The peristaltic pump was chosen because this pump has no possibility of leakage (no sealing) and no product contact part. This can be helpful if you want to add liquid fertilizer to your plant water media. Another advantage is that when the pump stops, the liquid flow is completely prevented. This is an advantage because if you use a centrifugal pump and your supply water tank is standing higher than your Bonsai pot, even when the pumps is not active the water flow goes on due to gravity.

Step down converter (XL4005 DSN5000 beyond LM2596 DC-DC adjustable step-down 5A power supply module, AliExpress 1.04 US $): This component is needed to regulated the voltage down from 12V to the requirement of your peristaltic pump.

Power Supply (AC 100-240V to DC 12V 2A Power Adapter Supply, Aliexpress 3.33 US $): The power adapter should provide 12 V for the timer and enough current in order to operate the pump.

Power socket connector (5.5*2.1 / 5.5 x 2.1 mm DC Power Socket/ DC Connector DC-053, Aliexpress 0.7 US $)

Preglued edging strips: The product actually is made to cover the raw edges of cut plywood. The strip has hot-melt adhesive preapplied to the back. You simply hold the strip in place, run over it with a household iron to heat the adhesive, let it cool and trim the edges. Here I used the larges strips I could find (4.5cm) and instead of fixing it to plywood they are glued directly on the cardboard. Sharp edges are removed by lightly sanding with 120-grit sand paper.

Socket-terminal strips: Normally socket-terminal strips are used to connect wires. Here the isolating plastic is taken apart and the metal piece is saved. Tubing is inserted through the metal piece and with the help of the screws the tube is squeezed in order to regulate the water flow.

Additional parts and tools:

  • Iron
  • Hot glue gun
  • Cardboard
  • Tubing
  • Cable ties
  • Water tank taken from distilled water
  • Soldering station
  • Voltage meter

Step 3: Housing

Cut the pieces for the housing out of cardboard. Make the opening for the power connector, the peristaltic pump and the timer. With a hot glue gun combine all the cardboard pieces to complete the housing.

The housing thereafter is covered with pre-glued edging strips. I took the larges strips I could find (4.5 cm). There are also other colors than white available. The product (pre-glued edging strips) actually is made to cover the raw edges of cut plywood. The strip has hot-melt adhesive preapplied to the back. You simply hold the strip in place, run over it with a household iron to heat the adhesive, let it cool and trim the edges. Sharp edges are removed by lightly sanding with 120-grit sand paper. In this way you can make your housing splash water proof.

Make 4 holes into the front near the opening for the peristaltic pump. These holes are used to fix the pump to the housing by the use of cable ties.

Step 4: Wiring

First solder all wires to the power connector. Then combine the power connector with the Timer and the Step-Down-Converter as per the wiring diagram. Power up the system – you will see the LED light on the Step-Down-Converter. Measure the voltage with a voltage meter. Adjust the voltage with a screw driver to the voltage required by your pump. Then solder the peristatic pump to the Step-Down-Converter and make a test run before gluing it to your housing.

Step 5: Combine Everything

Fix the equipment that you have prepared under the previous chapter into the housing with hot glue. Prepare a piece of Styrofoam so you can use it as a platform for the pump on your water tank. Plastic bottles in which you buy distilled water are very useful as water tank since they have a separate opening. In this way you can place the platform for the watering system on top of the tank but you still have an opening left for your tubing.

Place the tank on the window board. Push the Styrofoam platform onto the lid of the tank. Place the finished housing with the pump on the platform. One end of the tubing is placed in the tank. The other end of the tubing is connected to the drip system. Connect the power supply and program the timer according to the requirements of your plant.

Use the manual “On/Off”-switch of the timer to calibrate the watering duration. In addition, used the screws on the drip irrigation system to regulate watering.

Note for those who made it:

  • Even if you have automated your plant watering the timer is only working when set to “Auto”.
  • Don’t forget to program the “Off”–Time on your system because otherwise your tank will flood the pot and in addition the pump runs until you come back from holidays (smile).
  • Observe the system at least for two days before you go on holidays.

You see I had also some bad experience – but I share it with you. Now it is your turn to share information. Please give feedback.