ESP32 - Water/Liquid Valve
This tutorial instructs you how to control a liquid flow such as water, beer, oil by using ESP32 and a solenoid valve. It is the same for controlling gas flow.
To switch the valve, you can use a relay or a MOSFET module. Both of them only open and close the valve, because a solenoid valve is either open or closed. The MOSFET module has other good points: it makes no click, it switches faster, and it has no contacts that wear out. This tutorial covers both options.
This tutorial shows how to program the ESP32 using the Arduino language (C/C++) via the Arduino IDE. If you’d like to learn how to program the ESP32 with MicroPython, visit this ESP32 MicroPython - Water/Liquid Valve tutorial.
Hardware Used In This Tutorial
Or you can buy the following kits:
| 1 | × | DIYables ESP32 Starter Kit (ESP32 included) | |
| 1 | × | DIYables ESP32 S3 Starter Kit (ESP32 S3 included) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Introduction to Water/Liquid Valve
Pinout
Solenoid Valve usually has two terminals:
- Positive (+) pin (red): needs to be connected to 12V of DC power supply
- Negative (-) pin (black or other): needs to be connected to GND of DC power supply
How Water/Liquid Valve works
Normally, the valve is closed. When 12V DC is applied to the two terminals, the valve opens and water/liquid can flow.
※ NOTE THAT:
- For some kinds of valve, there is a gasket arrangement inside, so there is a minimum pressure requires to open the valve (after 12V DC is applied). The pressure can be created by liquid flow.
- For some kinds of valve, liquid can only flow one direction.
How to Control Water/Liquid Solenoid Valve
If the valve is powered by 12V power supply, it opens. To control the valve, we need to use a relay in between ESP32 and valve. ESP32 can control the solenoid valve via the relay. Learn more about relay in the ESP32 - Relay tutorial
The valve can also be driven by a MOSFET module. You can find its pinout and working principle in the ESP32 - MOSFET Module tutorial.
Relay vs MOSFET Module for Solenoid Valve
| Relay | MOSFET Module | |
|---|---|---|
| Valve control | open/close | open/close (no PWM for a valve) |
| Click sound | yes | no |
| Reaction time | slower, a few milliseconds | very fast |
| Wear | contacts wear out after many cycles | no moving contacts |
| Valve type | AC or DC valve | DC valve only |
| Valve voltage | any (as rated) | about 6V or more, 12V is fine |
| Isolation | yes (coil and contacts) | yes (PC817 optocoupler) |
| Suits | AC valves, rare switching | 12V DC valves that open and close often, quiet places |
For a 12V DC valve that switches many times a day, the MOSFET module lasts longer and stays quiet. For an AC valve, use the relay. Do not send a PWM signal to the valve; give it only full ON or full OFF.
Wiring Diagram
- How to connect ESP32 and water/liquid valve using breadboard (powered via USB cable)
This image is created using Fritzing. Click to enlarge image
- How to connect ESP32 and water/liquid valve using breadboard (powered via Vin pin)
This image is created using Fritzing. Click to enlarge image
- How to connect ESP32 and water/liquid valve using screw terminal block breakout board (powered via USB cable)
- How to connect ESP32 and water/liquid valve using screw terminal block breakout board (powered via Vin pin)
If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: The best way to Power ESP32 and sensors/displays.
ESP32 Code
The below code repeatedly turns the water valve ON in five seconds and OFF in five seconds,
Quick Instructions
- If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
- Do the wiring as above image.
- Connect the ESP32 board to your PC via a micro USB cable
- Open Arduino IDE on your PC.
- Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
- Copy the above code and paste it to Arduino IDE
- Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
- Check the water flow
Code Explanation
The above ESP32 code contains line-by-line explanation. Please read the comments in the code!
How to Control Water Valve with MOSFET Module
This part shows how to open and close the same valve with a MOSFET module instead of the relay. The relay and the MOSFET module use different pins on this page: the relay uses GPIO16, and the MOSFET module uses GPIO18. So each wiring has its own code.
Wiring Diagram with MOSFET Module
This image is created using Fritzing. Click to enlarge image
| From | To |
|---|---|
| ESP32 GPIO18 | Module PWM pin |
| ESP32 GND | Module GND pin |
| 12V adapter + | Module + terminal |
| Valve + (red) | Module + terminal (shared with the adapter +) |
| Valve − | Module LOAD terminal |
| 12V adapter − | Module − terminal |
The valve has a coil, so add a flyback diode (1N4007 or 1N5819) across the valve terminals, with the stripe (cathode) on the valve + side.
ESP32 Code for MOSFET Module
The code is the same idea as the relay code: HIGH turns the valve ON (open) and LOW turns it OFF (closed). The valve opens for 5 seconds and closes for 5 seconds, again and again.
A solenoid valve must only get full ON or full OFF, never PWM. This is why this page does not use the fade code from the MOSFET module tutorial.
Quick Instructions
- Do the wiring as in the MOSFET diagram above.
- Connect the ESP32 board to your PC via a USB cable.
- Open Arduino IDE and select the ESP32 board and COM port, as in the relay Quick Steps above.
- Copy the above code, paste it to Arduino IDE and click Upload.
- Check the water flow: the valve opens for 5 seconds and closes for 5 seconds.
Tip: the MOSFET module is for DC valves with a supply of about 6V or more. For an AC valve, keep the relay.
Video Tutorial
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