LDR (Light Dependent Resistor) + module
by Generic
SKU: PSA-CMP-LDR
No reviews yetTypical India street price
₹10–₹40
Resistance falls as light rises — day/night and brightness sensing.
Interface: Analog
Analog LDR module into A0 for day/night Blockly logic.
AO → A0
Blockly: sense_ldr, sense_light
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Concept
A photoresistor is a light-controlled resistor.
A little theory
CdS (or similar) photoconductivity: more photons → more carriers → lower R. Used in a voltage divider into ADC. In the classroom, treat LDR (Light Dependent Resistor) + module as a beginner part using Analog. Typical India street price is about ₹10–₹40. Always verify voltage and pin labels on your exact module — silk screens vary across clones. Start with a datasheet or trusted learn guide, power the part correctly, share GND with the MCU, and test with a simple blink/read sketch before building the full project. Measure voltages with a multimeter when something fails, and keep actuator current off the MCU regulator.
How it works in a project
Module: AO analog, DO digital via comparator. Bare LDR: 10 kΩ resistor to 5 V, tap to A0.
Classroom & project use
- Street-light auto
- Solar tracker (dual LDR)
- PSA Lab light HUD
Buying in India
Precautions
- CdS LDRs are slow and not RoHS-favourite — for school demos they remain standard
- Share a common GND with the microcontroller
Specifications
| Dark | MΩ range |
| Light | few hundred Ω |
| Peak response | visible light |
| Category | Sensors |
| Difficulty | Beginner |
| Voltage | Analog divider (3.3–5V) |
| Interface | Analog |
Pinout
VCC | GND | AO (and DO if comparator module)
