Light Sensitive LDR Relay Module 5V — Auto Night Light Controller, 10A SPDT, Adjustable Threshold
Light Sensitive LDR Relay Module 5V Auto Night Light Controller, 10A SPDT, Adjustable Threshold
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Light Sensitive LDR Relay Module — 5V, 10A SPDT, Automatic Light-Level Switching
The Light Sensitive LDR Relay Module is a self-contained automatic switching module that energizes or de-energizes a 10A relay based on ambient light level — no microcontroller required. Connect 5V power, wire your load to the relay terminals, adjust the onboard potentiometer to set the brightness threshold, and the module automatically switches your load ON or OFF as light levels change. The included LDR (Light Dependent Resistor) sensor on a 10″ (25cm) lead allows remote positioning of the sensor away from the module.
Typical use: automatically turn on a security light, garden light, or night light when ambient brightness drops below a preset level at dusk, and turn it off at dawn — completely autonomously, without any programming or microcontroller.
Key Features
- Fully autonomous operation — no microcontroller or programming required
- Adjustable light threshold — onboard potentiometer sets the brightness trip-point (CW = higher threshold)
- 10A SPDT relay contacts — switches up to 250VAC @ 10A or 15VDC @ 10A
- Both NO and NC contacts — switch load ON or OFF when light drops below threshold
- Remote LDR sensor — 10″ (25cm) lead for flexible sensor positioning; extendable by splicing
- Blue LED indicator — illuminates when relay is energized
- Red power LED — confirms 5V supply is connected
- Built-in flyback diode — protects against relay coil back-EMF
- Reverse polarity protection — diode on 5V power input
- LM393 comparator IC — stable, hysteresis-free threshold detection
Technical Specifications
| Supply Voltage | 5V DC |
| Supply Current | ~5mA (relay off) / ~55mA (relay energized) |
| Relay Contact Rating (AC) | 115VAC @ 10A / 250VAC @ 10A |
| Relay Contact Rating (DC) | 15V DC @ 10A (recommended max) |
| Relay Type | SPDT (NO + NC + COM) |
| Threshold Adjustment | Onboard potentiometer (CW = higher threshold) |
| Sensor | LDR on 10″ (25cm) lead |
| Comparator IC | LM393 |
| PCB Dimensions | 53 × 31 × 20mm (2.09 × 1.2 × 0.79″) |
Wiring Guide
Power (2-pin screw terminal):
- Vcc → 5V DC supply
- GND → Ground
Load (3-pin screw terminal):
- NO (top) → Load connects here to switch ON when relay energizes (light drops below threshold)
- COM (center) → AC or DC power source for the load
- NC (bottom) → Load connects here to switch ON when relay de-energizes (light above threshold)
Theory of Operation
The LDR sensor resistance increases as ambient light decreases. An LM393 voltage comparator monitors the LDR voltage divider output against the potentiometer-set reference voltage. When brightness drops below the threshold, the comparator output switches, energizing the relay (blue LED ON). When brightness rises above the threshold, the relay de-energizes (blue LED OFF). The potentiometer adjusts the reference voltage — turning CW raises the threshold, making the module trigger at higher light levels.
Important Notes
- DC voltage limit: Relay contacts can become sticky above ~15V DC. Limit DC switching to 15V or below.
- AC performance: Tested successfully switching a 1500W / 12.5A heater load without issues.
- Threshold calibration: Point LDR at light source, adjust pot until blue LED just turns off. Shielding LDR should then trigger the relay.
- AC safety: When switching mains AC voltage, ensure all connections are properly insulated and inaccessible.
Typical Applications
- Automatic dusk-to-dawn security light and garden light controller
- Night light and corridor light automation
- Greenhouse supplemental lighting controller (lights on when dark)
- Photography darkroom safelight automation
- Aquarium lighting automatic day/night cycle
- Industrial machine light-level interlock
Package Contents
- 1 × Light Sensitive LDR Relay Module 5V
- 1 × LDR sensor on 10″ (25cm) lead
- ★Product Description
- ★About us
- ★Custom cable
Light Sensitive LDR Relay Module — 5V, 10A SPDT, Automatic Light-Level Switching
The Light Sensitive LDR Relay Module is a self-contained automatic switching module that energizes or de-energizes a 10A relay based on ambient light level — no microcontroller required. Connect 5V power, wire your load to the relay terminals, adjust the onboard potentiometer to set the brightness threshold, and the module automatically switches your load ON or OFF as light levels change. The included LDR (Light Dependent Resistor) sensor on a 10″ (25cm) lead allows remote positioning of the sensor away from the module.
Typical use: automatically turn on a security light, garden light, or night light when ambient brightness drops below a preset level at dusk, and turn it off at dawn — completely autonomously, without any programming or microcontroller.
Key Features
- Fully autonomous operation — no microcontroller or programming required
- Adjustable light threshold — onboard potentiometer sets the brightness trip-point (CW = higher threshold)
- 10A SPDT relay contacts — switches up to 250VAC @ 10A or 15VDC @ 10A
- Both NO and NC contacts — switch load ON or OFF when light drops below threshold
- Remote LDR sensor — 10″ (25cm) lead for flexible sensor positioning; extendable by splicing
- Blue LED indicator — illuminates when relay is energized
- Red power LED — confirms 5V supply is connected
- Built-in flyback diode — protects against relay coil back-EMF
- Reverse polarity protection — diode on 5V power input
- LM393 comparator IC — stable, hysteresis-free threshold detection
Technical Specifications
| Supply Voltage | 5V DC |
| Supply Current | ~5mA (relay off) / ~55mA (relay energized) |
| Relay Contact Rating (AC) | 115VAC @ 10A / 250VAC @ 10A |
| Relay Contact Rating (DC) | 15V DC @ 10A (recommended max) |
| Relay Type | SPDT (NO + NC + COM) |
| Threshold Adjustment | Onboard potentiometer (CW = higher threshold) |
| Sensor | LDR on 10″ (25cm) lead |
| Comparator IC | LM393 |
| PCB Dimensions | 53 × 31 × 20mm (2.09 × 1.2 × 0.79″) |
Wiring Guide
Power (2-pin screw terminal):
- Vcc → 5V DC supply
- GND → Ground
Load (3-pin screw terminal):
- NO (top) → Load connects here to switch ON when relay energizes (light drops below threshold)
- COM (center) → AC or DC power source for the load
- NC (bottom) → Load connects here to switch ON when relay de-energizes (light above threshold)
Theory of Operation
The LDR sensor resistance increases as ambient light decreases. An LM393 voltage comparator monitors the LDR voltage divider output against the potentiometer-set reference voltage. When brightness drops below the threshold, the comparator output switches, energizing the relay (blue LED ON). When brightness rises above the threshold, the relay de-energizes (blue LED OFF). The potentiometer adjusts the reference voltage — turning CW raises the threshold, making the module trigger at higher light levels.
Important Notes
- DC voltage limit: Relay contacts can become sticky above ~15V DC. Limit DC switching to 15V or below.
- AC performance: Tested successfully switching a 1500W / 12.5A heater load without issues.
- Threshold calibration: Point LDR at light source, adjust pot until blue LED just turns off. Shielding LDR should then trigger the relay.
- AC safety: When switching mains AC voltage, ensure all connections are properly insulated and inaccessible.
Typical Applications
- Automatic dusk-to-dawn security light and garden light controller
- Night light and corridor light automation
- Greenhouse supplemental lighting controller (lights on when dark)
- Photography darkroom safelight automation
- Aquarium lighting automatic day/night cycle
- Industrial machine light-level interlock
Package Contents
- 1 × Light Sensitive LDR Relay Module 5V
- 1 × LDR sensor on 10″ (25cm) lead
