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3.6 Controlling a Water Pump

In this lesson, we’ll learn how to control a small water pump using the Raspberry Pi Pico 2 and an L293D motor driver. A small centrifugal pump can be used for projects like automatic plant watering systems or creating miniature water features. Controlling the pump is similar to controlling a DC motor, as it uses the same principles.

What You’ll Need

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Newton Lab Kit	450+	Newton Lab Kit

You can also buy them separately from the links below.

SN	COMPONENT	QUANTITY	LINK
1	Raspberry Pi Pico 2	1	BUY
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	IC L293D	1
6	Power Supply Module	1
7	9V Battery	1
9	DC Water Pump	1

Important Notes Before You Begin

Pump Setup: Connect the tubing to the pump’s outlet. Submerge the pump in water before powering it on.
Avoid Dry Running: Ensure the pump is always submerged. Running the pump dry can cause overheating and damage the motor.
Prevent Clogging: If you’re using the pump for watering plants, make sure the water is free of debris to prevent clogging.
Priming the Pump: If water doesn’t come out initially, there might be air trapped in the tubing. You may need to prime the pump by allowing water to flow through to remove air bubbles.

Circuit Diagram

sch_pump

L293D is a motor driver chip, EN is connected to 5V to make L293D work. 1A and 2A are the inputs connected to GP15 and GP14 respectively; 1Y and 2Y are the outputs connected to the two ends of the motor.

Y (output) is in phase with A (input), so if GP15 and GP14 are given different levels respectively, the direction of motor rotation can be changed.

Wiring Diagram

In this circuit, you will see that the button is connected to the RUN pin. This is because the motor is operating with too much current, which may cause the Pico to disconnect from the computer, and the button needs to be pressed (for the Pico’s RUN pin to receive a low level) to reset.

Writing the Code

Note

You can open the file 3.6_pumping.ino from newton-lab-kit/arduino/3.6_pumping.
Or copy this code into Arduino IDE.
Select the Raspberry Pi Pico 2 board and the correct port, then click “Upload”.

const int IN1 = 15; // GPIO pin connected to Input 1A
const int IN2 = 14; // GPIO pin connected to Input 2A

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
}

void loop() {
  // Turn the pump on
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  delay(5000); // Run for 5 seconds

  // Stop the pump
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  delay(5000); // Stop for 5 seconds
}

After uploading the code:

The pump should run for 5 seconds, pumping water through the tubing.
Then, it will stop for 5 seconds.
This cycle repeats indefinitely.
If water doesn’t flow initially, make sure the pump is submerged, and there are no air bubbles in the tubing.

Safety Precautions

Water and Electricity:
- Be extremely careful to keep water away from the Pico and other electronic components.
- Ensure all connections are secure and insulated if necessary.
Power Supply:
- Use a power supply that matches the pump’s voltage requirements (typically 3V-6V).
- Do not power the pump directly from the Pico’s 3.3V pin.
Current Draw:
- Pumps can draw significant current.
- Ensure your power source can handle the pump’s current requirements.
Resetting the Pico:

If you encounter issues uploading code after running the pump, you can manually reset the Pico by connecting the RUN pin to GND momentarily.

Further Exploration

Automated Plant Watering:

Incorporate soil moisture sensors to automate the watering process based on soil dryness.
PWM Speed Control:

Use Pulse Width Modulation (PWM) to control the pump’s speed by varying the voltage.
Timing and Scheduling:

Implement more complex timing using real-time clocks or schedulers.

Conclusion

In this lesson, you’ve learned how to control a small water pump using the Raspberry Pi Pico and the L293D motor driver. This technique can be used in various projects like automated plant watering systems, fountains, or hydroponic setups.