4/18/2024 0 Comments Arduino mega 2560 pinout diagramThe following subsections highlight the main Arduino Uno and Arduino MEGA 2560 pins. In addition the basics of PWM pins are explained. This part of the tutorial includes more details on digital input and output pins. Digital Arduino input and output pins are briefly covered in part 8 of this tutorial on how to use a push button switch with Arduino. Thirdly some pins have special functions such as serial communications and PWM (Pulse Width Modulation). Secondly as an output to switch or drive an electric load such as an LED. Firstly input pins for reading the state of a pin, or attached switch for example. A value below 700 causes the sketch to switch the LED off.Basically, Arduino digital pins are configurable between three different functions as follows. That is, when the LDR is covered and dark. Afterwards it switches the Arduino on-board LED on if the analog value is above 700. The following sketch code reads the analog value on analog input A0 of the Arduino. Switch on an LED when Light Levels are Low Another reason that analog values differ is because of different levels of ambient light. This is the reason that you may have a different reading. Use a value slightly below the reading that you get if your value differs. For example, use a value of 700 to switch on an LED if the high value is around 750. Take note of the values as the high value is used in the next sketch. After covering the LDR, this value goes up to about 750. As a result, the analog value increases.Īs an example, a value of around 300 is read in ambient light. Take note what the value is and then cover the LDR sensor surface. The serial monitor window displays a raw analog value from the LDR circuit. Finally, open the Arduino IDE serial monitor window. Afterwards, upload this sketch to the target Arduino board that has the LDR circuit attached. Select File → Examples → 01.Basics → AnalogReadSerial from the top Arduino IDE menu bar. Get the LDR Circuit Analog ValueĪs in previous parts of this tutorial, open the Analog Read Serial sketch. The second sketch turns on an LED when the LDR top surface is darkened. This sketch displays the raw analog value read from the LDR. The first sketch is a built-in example sketch. Two sketches are presented in the subsections that follow. Arduino MEGA 2560 LDR Breadboard Circuit Arduino LDR Tutorial Sketch Code Build this circuit if you have an Arduino MEGA 2560. The image below shows the same circuit above, but attached to an Arduino MEGA 2560 board. Arduino Uno LDR Breadboard Circuit Arduino MEGA 2560 LDR Breadboard Circuit Build this circuit as shown and connect it to the Arduino Uno, if this is the board that you have. The image below shows the above circuit on breadboard and connected to an Arduino Uno. This causes the voltage between GND and A0 to vary as well. As light varies on the LDR surface, so does its resistance. That is, the voltage at the junction of R1 and R2 is the divided voltage from the 5V that is across them. In the above Arduino LDR circuit diagram, 10k resistor R1 and LDR R2 form a voltage divider. Additionally, connect the 10k resistor between A0 and 5V. That is, connect the LDR between the A0 pin and GND. Connect an Arduino MEGA 2560 in the same way. Notice that the circuit uses an Arduino Uno. The circuit below shows how to connect a LDR / photoresistor / photocell to an Arduino. For example switch on a room light, or shine a torch on the LDR. Observe that the resistance decreases with decreased light. Cover the LDR top surface using your finger. Afterwards, check the resistance reading on the multimeter. Put the multimeter onto the resistance or ohms scale. Plug the LDR into a breadboard so that it is easier to handle. If you have a multimeter, try the following. LDR Circuit Connected to an Arduino MEGA 2560 used in this Arduino LDR Tutorial This Arduino LDR tutorial uses the circuit to detect light levels and switch an LED on or off. The following image shows a LDR connected in series with a 10k resistor. In addition the article shows two common LDR symbols used in circuit diagrams. The LDR (Photoresistor) for Beginners in Electronics article has more basic information on these devices. Conversely less light or more darkness on the LDR surface causes its resistance to increase. That is, as more light shines on the LDR, its resistance decreases. A LDR is a type of resistor that changes resistance as light on its surface changes. Additionally, it is known as a photoresistor or photocell. What is a LDR, Photoresistor or Photocell?
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