Low-cost Automatic Watering System by Automation Relay Module

I will introduce a watering system using an automation relay module.

No special programming is required. All you need to do is connect the water pump and battery, set the operation mode and time, and you can create a low-cost and highly functional automatic watering system.

I made two model of watering system, one that runs on batteries and one that runs on a USB power adapter. The battery-powered one is for a low-power pump, and the USB-powered type is for indoor use or for a high-power pump.

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I am growing vegetables and flowers in pots outdoors and they need watering in the morning and evening especially during the hot summer season. Since I am planning to go on a trip for a few days, I prepared an automatic watering system.

I thought about buying a cheap automatic watering system online, but buying multiple units would be quite expensive. I need multiple watering devices because the pots are far apart, and the amount of water needed to water them is too much for one tank.

I was prototyping a watering system using Arduino, but then I found an automation relay module that was easier to wire and cheaper, so I decided to use that instead.

These supplies can be purchased online.

Common Supplies for both model:

• Automation relay module ( sample )

There are two types of USB connectors, with and without Micro USB or Type-C. I recommend the type with USB connector.

• Watering hose( sample )

The size ID5/OD7mm or ID6/OD8mm will fit your water pump nozzle. I recommend using silicone resin for the hose material rather than polyvinyl chloride resin, as it is more flexible and less prone to bending.

Model A: Battery powered

• Water pump( sample )

There are various types, such as horizontal and vertical types, but any of them will do. It is preferable that the power supply specification supports 5V-12V. Pumps with USB connectors seem to be limited to 5V power supply, so you need to devise a way to operate them at 5V.

• Jumper wires

A single wire cable connecting the relay module's power supply (6.0-30V) and COM.

A 2-core wire cable to connect the water pump and the relay module as needed.

• 9v battery(006P) snap connector( sample )

If you require longer operation times, consider increasing your battery capacity with 6 slots AA Battery Holder ( sample ) or 2 Slot 18650 Battery Holder ( sample ).

Model B: USB powered

• Water pump with USB plug( sample )

There are various types, such as horizontal and vertical types, but any of them is ok.

• USB Extension Cable Extender A Male to Female( sample )

Use the female connector side.

• USB AC Adapter / USB cable

Some water pump consume a lot of power, so use an AC adapter with a large capacity (2A up).

Optional:  

• Automatic Watering System Kit ( sample )

If you want to branch out the water supply, it's easiest to purchase a kit that includes connectors and hoses.

The automation relay module is equipped with a microcontroller, so you can set the relay to turn on/off at any time you like! (Can be set from 0.1 seconds to 999 minutes)

Furthermore, seven different operating modes can be set, and it can also be powered by a USB 5V power supply, making it extremely versatile. 

This watering system uses the "P3.2" operation mode. In this mode, the system can be set to operate in such a way that "one minute of water supply is repeated 24 times at 4-hour intervals".

How to set parameters?

1. The module is powered up, the display at the current work mode (P1.1 default mode), then enter the main interface; press "SET" button for 2 seconds after release to enter mode selection interface; a short time by pressing "UP", "DOWN" key to select the mode (P3.2).
2. Select the mode (such as P3.2), short press the "SET" button, then the parameter to be set flashes ( "OP" on-time, "CL" off time, "LOP" cycles ( "---" represents infinite loop)), by "UP", "DOWN" keys to adjust the parameter value, support long press (rapid increase or decrease) and short press (increase or decrease one unit); then short press the "STOP" key to select the decimal point position, select the time range (0.1 seconds to 999 minutes); short press the "SET" button to set the next parameters of the current mode of procedure is as above.
3. After the parameters are set, long press "SET" button for 2 seconds then release, the name of the current mode will flash once, and then return to the main screen, set the parameters of success!

How to choose the time range?

After setting the mode selection screen parameter value by a short press "STOP" button to select the time range;

• x x x. decimal point in the unit place, Timing range: 1 second to 999 seconds.
• x x.x decimal point in decade place, Timing range: 0.1 seconds to 99.9 seconds.
• x.x.x. decimal full brightness, Timing range: 1 minute to 999 minutes.

For example, to set "OP" to 60 seconds, move the decimal point so the digital display reads "060." or "60.0".

For example, to set "CL" to 4 hours, set 240 minutes. Move the decimal point so that the digital display reads "2.4.0."

Relays enable mode:

In the main interface, short press the "STOP" button to switch between ON and OFF, the current in which the state will flash, and then return to the main screen. (This feature is an emergency stop function, click off the relay)

• ON: Relay allows conduction in the "OP" on-time
• OFF: relay prohibit conduction is always closed

Sleep mode:

Press the "STOP" button for two seconds and then release to switch "C-P" and "O-d" state, in which the current state of flashes and then return to the main screen.

• "C-P" Sleep mode: five minutes without any operation, the digital display automatically turns off, the program running as usual
• "O-d" normal mode: digital display always open

The number of parts is reduced by sharing the power supply between the relay module and the pump.

• Wire the positive battery wire to VCC(6.0-30V)
• Wire the negative battery wire to GND
• Wire VCC(6.0-30V) and COM with a jumper wire
• Wire the positive pump wire to NC
• Wire the negative pump wire to GND

How long can it be operated with 006P dry cell battery?

Battery consumption depends on the amount of time the pump is running. The current when the pump is running is about 140 mA, and the current when it is in standby is about 3 mA.

Let us estimate the case where the pump operates for one minute every four hours. Assuming the capacity of the 006P dry cell battery to be 400 mAh, it should last about 4 days, but in reality, the relay module will repeatedly restart after 2 days because of the high current flow during pump activation.

Since operating times vary depending on the environment, I recommend several trial runs before actual operation.

How to make it work longer?

Separating the power supplies for the relay and pump will increase the number of components, so consider increasing the battery capacity. To increase battery capacity, use a 6-slot AA battery holder ( sample ) or a 2-slot 18650 battery holder ( sample ).

Wire the pump so that the power supplied by the USB connector flows to the pump.

• Wire the +5V of the USB connector to COM
• Wire the GND of the USB Extension Cable to the GND of the USB connector (black wire)
• Wire the +5V of the USB Extension Cable to the NO (red wire)

The USB Extension Cable is secured to the relay module with a cable tie or hot bond.

Can't I use a mobile battery as a power source?

Many mobile batteries have a feature called auto power-off. This feature automatically turns off the power supply when the mobile battery is used below a certain amperage. The standby current of the relay module is about 3A, so the auto power-off function will stop supplying power. If you use a mobile battery, use one that does not have an auto power-off function.

I did not buy a large tank, but set a plastic bag in a large flowerpot to hold the water. The water in the photo is blue because liquid fertilizer is added.

For water distribution, I used the Automatic Watering System Kit ( sample ) . The kit also comes with a hose, but I use a silicone hose because it is more flexible and easier to use. The pump used here is not powerful, so the hose is branched into smaller sections to ensure that water is distributed evenly.

Be aware of the water level

The tank should be positioned so that the water surface is lower than the outlet of the watering hose. If the water surface is higher than the outlet of the water hose, water will continue to flow out due to the siphon principle after the pump stops.

How big a tank of water do you need?

The amount of water required depends on the length of time the pump is running. Running the pump for 1 minute will distribute 1 to 2 liters of water. In my environment with Micro Submersible Water Pump, it distributes 1.4 liters of water per minute.

If you run the pump for one minute every 4-hours, you will need about 10 liters per day. If a large tank is not available, it is necessary to provide multiple watering system to shorten the pump operation time.