Light Sensitive Relay Module 5V

Automatically control a load based on ambient light detection.

DESCRIPTION

The Light Sensitive Relay Module 5V can automatically control a load such as a night security light based on the ambient light level.

PACKAGE INCLUDES:

• Light Sensitive Relay Module 5V

KEY FEATURES OF LIGHT SENSITIVE RELAY  MODULE 5V:

• Built-in photodiode sensor automatically controls the relay based on light intensity.
• Detects both visible and infrared light
• Adjustable light level set-point
• Controls loads of 115/230VAC @ 10A
• Controls loads of 0 – 15VDC @ 10A
• LED indicator when relay is energized
• 5V power operation

This is a self-contained switching module that energizes / de-energizes a relay based on the the detection of light, both visible and infrared.   Just add 5V power and hook up the load you want to control then adjust the potentiometer to set the brightness level at which you want the relay to switch between ON / OFF.

This type of module can be used for applications such as to automatically turning a light on when the ambient brightness goes below a preset level as might be the case for a outside security light or night light.  It can also detect a flame under some conditions.

The diode is sensitive primarily to light that strikes it from the rounded end rather than the side which gives the sensor some directionality.

Theory of Operation

The light sensor on the module is a light detecting photodiode .

The brightness level trip-point for triggering the relay can be adjusted using the potentiometer on the module.  Turning the pot CW increases the brightness trip-point.

When the brightness goes over the trip-point value, an LM393 voltage comparator IC energizes the relay and it switches ON.  A green LED is illuminated when the relay is energized.

When the brightness drops below the preset value, the relay switches back OFF.

The relay has both NO (Normally Open) and NC (Normally Closed) contacts so the module can either be used to energize a load when brightness goes up past the trip-point value or when it goes down past that level.

A flyback diode is included on the module in parallel to the relay coil to safely shunt current when the relay coil is de-energized.

Module Connections

POWER

The module requires 5V power and ground to operate.  There is a red LED that is lit when power is applied to the module.   When the relay is energized, the module draws about 80mA from the Vcc pin.

1 x 2 Header (Power Connections)

• Vcc = Connect to 5V power supply
• GND = Connect to ground of the 5V power supply

LOAD

The output of the relay is rated to switch up to 30VDC at 10A or up to 250VAC at up to 10A (See our notes below).

The output is SPDT type with both a NO (Normally Open) terminal and a NC (Normally Closed) terminal relative to the COM terminal.  When the relay is de-energized (green LED OFF) the NO-COM is open and the NC-COM is shorted.  When the relay is energized (green LED ON) the NO – COM is shorted and the NC-COM is open.

1 x 3 Screw Terminal (Load Connections)

• Top = Normally Open relay contact – Load is connected to this terminal if it should switch ON when relay is energized.
• Center = Common connection – Connects to AC or DC power source for load that is being controlled.
• Bottom = Normally Closed relay contact – Load is connected to this terminal if it should switch ON when relay is de-energized.

OUR EVALUATION RESULTS:

These are nice inexpensive modules that will work for a number of applications and allow you to control devices based on sensing presence or absence of light without the need to have an MCU involved.  Just hook up 5V power and your load and you are all set.

The sensing works best when detecting a brighter light source and can be set to be fairly sensitive and detect shadows or other changes in the light intensity.  Under fairly low light level changes, the sensor may not detect a difference as easily.  Some amount of empirical testing and adjustment is usually need to find the right adjustment point.

We do find the DC rating of the relay to be too aggressive. With DC voltages above about 15V, the contacts can become a little sticky. We recommend using it to switch DC voltages of no more than 15V.

With AC, the relays performed very well in our testing.  To test the upper limit we used it to switch a 1500W heater that draws about 12.5A and the relay handled it without any problems.

To test the device, connect it to 5V.  While pointing the photodiode towards a light source, adjust the pot so that the green LED just comes on.  Shielding the photodiode from the light should then cause the green LED to go off and an audible click can be heard from the relay as it switches.

BEFORE THEY ARE SHIPPED, THESE MODULES ARE:

• Sample inspected and tested per incoming shipment

Notes: 

1. None

TECHNICAL SPECIFICATIONS