Build A LDR Sensor Monitoring The Room Temperature

In this project we will monitor the room temperature using a LDR_NSL19_M51 light dependent resistor (LDR) and 4Duino. The resistance of the LDR varies significantly with ambient light hence it can detect surrounding light intensity changes in real time. In this project 4Duino’s resistive touch display is used as a means for displaying the detected light intensity using LED digits and an angular meter.

LDR Sensor



  • 4Duino
  • LDR sensor
  • Bread Board
  • Jumper cables
  • µSD card
  • Micro USB cable


Step 1: Build

Build the circuit as shown in the following diagram and schematic.

Step 2: Program

Workshop 4 – 4Duino Extended Graphics environment is used to program this project.

This project requires the Arduino IDE to be installed as Workshop calls the Arduino IDE for compiling the Arduino sketches. The Arduino IDE however is not required to be opened or modified to program the 4Duino.

Open this file using Workshop 4.

Note: Download the project here.

Step3: Comms Port

Connect the 4Duino to the PC using µUSB cable.

Then navigate to the Comms tab and select the Comms port to which the 4Duino connected.

Step4: Compile and Upload

Finally, go back to “Home” tab and now click on the “Comp’nLoad” button.

The Workshop 4 IDE will prompt you to insert a µSD card to the PC in order to save the widget images. Insert µSD card, select the appropriate drive and press button “OK”.

If the µSD card has the widget images you can click button “No Thanks”.

LDR Sensor schematic

Step 5: Insert µSD card

After uploading the program in to the 4Duino, it will try to mount the µSD card. If the µSD card is not present it will prints an error message.


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