If you are designing your own intelligent “Graden Computer” with an optional digital plant moisture sensor/water pump controller that lights an LED to alert the user when it is time to water a potted ...

Here is the diagram of my Arduino infrared close proximity sensor. As you can see, the core part of my experimental setup is an Arduino UNO, but other compatible microcontrollers can also be employed.

Thermistors are another example of such sensors whose resistance changes when the operating temperature changes ... can see from that sketch and the circuit diagram, the LED is connected to the ...