Solar-Powered Automatic Plant Watering Device

For my first milestone, I am testing my circuit on a breadboard to ensure it works properly before soldering it onto a perfboard. The device utilizes a circuit to make sure the device only waters the plant when the soil is dry. See diagram below. The breadboard is connected to a 5 volt power supply to power the circuit. There is one soil and one water sensor electrode. These are both made of aluminum foil and are sensitive to moisture. Because of this sensitivity, when the soil is dry and when there is water in the reservoir, the motor will be powered. To implement the sensors into the circuit, two wires are connected to each using binder clips. If the water reservoir is empty it will pose high resistance because there is no water allowing electrons to flow easily. Similarly, if the soil is dry it will also pose high resistance because it is also more difficult for electrons to flow without water.  The circuit powers a water pump which will later be connected to a tube to transfer water into the plant container. The circuit utilizes a MOSFET transistor to turn on the pump only when the soil is dry. The MOSFET transistor has an insulated gate which can control conductivity based on the amount of applied voltage. A MOSFET works electronically like a switch. It varies the width of the channel where current is entering based on the voltage and can close the drain where current exits. In my circuit, the MOSFET is connected to the motor and sensors. Therefore, the MOSFET closes and opens the channel to supply power to the pump based on the sensors. When the the soil is dry, the MOSFET turns the pump on, and when the soil is dry it turns the pump off. The circuit also includes one NPN transistor and one PNP transistor which can act as switches. The NPN transistor is connected to the soil sensor and the PNP is connected to the water sensor. They are acting as switches to control two  LEDs which are also connected to the two sensors. The two LEDs are useful to test if each sensor is working. The circuit also has many resistors to control the flow of current and make sure the current will not overflow and short the circuit. The circuit also has a leaded semiconductor diode to make sure current flows in one direction through the pump. One difficulty when building this circuit is that there are many connections which can be easily miswired. It can be very tedious to build, but make sure to triple check that each connection is in the right place or else you can have a lot of trouble trying to figure out why the circuit is not working properly. I also learned how to test a circuit without using all the real components. For example, I used push buttons to first test the sensors and an LED to test the motor which is helpful to do before connecting larger components. I also was able to troubleshoot using a multimeter which is able to check the voltage between each connection.  It was very fun learning how to test a circuit on a breadboard.