Saturday, June 9, 2018

Simple Solar Plant Watering Alarm Circuit Based on Transistor

Electronic Kit School. - This is the simple circuit for sensor and alarm application to build solar plant watering automatically. This circuit will give you indicator as sound when the soil in the plant is drying. 

We thing this circuit is very simple and useful to you to save your plant from the die, rather that this circuit not need battery, but supply from solar cell. So, you can create this circuit to help your work at home.

The main component to build this circuit also very simple, consist of resistor, buzzer, transistor, LED, and also solar cell which popular today. In this time, beside we will show you the circuit, here we also will show you component part and global description about this circuit.


  1. Transistors Q1 and Q2
  2. Resistors R2 and R3
  3. Variable Resistor VR1
  4. LED1 and LED2
  5. Buzzer
  6. Solar Cell

Circuit like in Figure 1 above show you about the Simple Solar Plant Watering Alarm Circuit Based on Transistor. From Eleccircuit site describe that the main principle is that when the soil is dry, with high resistance. However, when the soil is wet with minimal resistance.

Usually the wet soil will have resistance is about 6K the electricity current will flow to the probes to base of transistor Q1-2N3904 ,makes it works conducting current from the positive voltage to CE to ground. Thus, the transistor Q2-2N2222 not has a bias current to base its, so Q2 not works no sound from a buzzer.

But when dry soil, high resistance between probes so there aren’t the current flow to base of Q1 so it not conducting. Thus the current from the positive flow to R1-10K to base of Q2 it works conducting current to Buzzer sound. LED1,LED is connected in series to display power on. R2 is used to limited current to LEDs.