Portfolio of Chi-Ching Tsai


Creativity is nothing but a mind set free.

First Play with Circuit

Materials |  Flat battery (3V), wires, LED, water, a pot, and plant

The subject is to make a sculptural or architectural or toy-like or just weird object with some LEDs and a homemade switch. The challenge is to use an unexpected material, and/or an unexpected behavior, and practice Ohm's Law on your own, verify with calculator.

Design Concept | The concept is to build a really simple biological sensor to detect the timing for watering flower. By placing the wire down to the bottom of the pot and pouring water into the flower pot, the wires, battery, resistance becomes a circuit which turns the LED on. Theoretically, the water will be absorbed by the plants and when there’s no water left at the bottom of the pot, the circuit will be broken off and lead LED shut down.

Schematic |

Difficulties | The first obstacles I came across was I cannot measure the resistance of water. The measured number showed on the multimeter kept floating. After that, there is no “beep” sound when I linked the multimeter with water, which could mean it’s not a circuit yet.

Problem Solving | First of all, I added some sea salt in the water (God please bless my plants). Then, I tried to ignore the signal of the multimeter and directly tested my assumption by linking all the materials together, and… Voila! It worked!


Actually, This was just an experiment and a beginner level project, so I did not take too many efforts on decorating the pot and hiding the wires lol. After all, the point of his project is to play with the wires and LED!

Playing with plants and wires, we can be natural and digital at the same time! I am happy that the project was quite successful in the end. There might be some points that I can improve next time:

  • To hide the wires, battery, and resistance.

  • Try to measure the time and see how much time will the LED turns off

  • Maybe try in an advanced way to connect the LED to my phone other devices and send notifications when it’s watering time.

Reference Links |

  • Here's a more in depth explanation of using Ohm's Law with LEDs.

  • Practice Ohm's Law on your own, verify with this calculator.  (note the question marks for help).  NOTE: this shows the next highest common resistor value, not the exact calculation.