Robotics 1.0 Lesson Plan
Lesson 16 - Water Wizard

Purpose:Connect a battery-powered motor pump to a relay and use the moisture sensor to detect soil moisture levels and water the plant automatically

No. of. Classes

1 - (Time : 1:30 minutes, Each group maximum 4 children).

Materials Required

Circuit express board (CPX) with USB cable and 5v battery.

Crickit

Photoresistor sensor.

Moisture sensor.

Relay sensor

Jumper wires

Water pump (5v or 9v)

Rechargable batteries 5v or 9v

Curriculum Content 6.5 Moisture Sensor
6.8 Photoresistor (external)
7.6.1 External Power for Actuators
7.6.2 External Power
7.6.3 External Power
7.7 Water pump
7.8.4 External Power – Wiring & Safety
Prior knowledge

Understanding of moisture sensors, relays, basic circuits, and safe handling of water with electronics..

Exercises

Exercise 1



`

Connect a battery-powered motor pump to a relay, read moisture levels of the soil and use the water pump to water the soil when it is dry.


  • View the connection of Moisture sensor, Photoresistor sensor and Relay with External battery with water pump here.

    IR Sensor Working

  • View the pseudocode to implement the exercise here


    • Solution


    Here is the Solution:

  • Click here to see the solution Video
  • View the code for Exercise 1 and its explanation
    • Teacher's Instruction
    1. Go around and check if students are facing any issues and help them troubleshoot.
    2. Explain why the moisture sensor value needs to be checked continuously to decide when watering is required.
    3. Discuss how this system can be used in real life, such as in greenhouses, home gardens and smart irrigation systems.
    4. Show how the relay safely switches the water pump on and off using a low-power signal from the Crickit.
    5. Explain why an external battery is needed for the water pump and why the Crickit alone cannot supply enough power.
    6. Emphasize safety while working with water and electricity, especially when using the relay and external power.
    7. Ask students to switch off the power, unplug all wires and carefully clean up after the activity.
    8. Why is it important to use a sensor and a relay to control the water pump instead of turning the pump on and off manually?
    9. What could happen if the relay fails to switch the pump off and how might you design the system to make it safer or more reliable?