Light Sensor Circuits

Dark Activated Switch or Porch Light Switch. This circuit activates a relay when the light level drops below a preset threshold. The light sensitivity can be adjusted using variable resistor VR1, and the relay contacts can control an external light or buzzer. The circuit includes two schematics: one for a light-activated relay and another for a dark-activated relay. When the light or dark condition reaches the sensor, a relay is triggered. The Dark Sensitive Switch operates a relay when the light falling on the light-dependent resistor (LDR) falls below a designated set point. The Door Minder kit utilizes an infrared beam to monitor doorways or passageways; when the beam is interrupted, a relay is activated, which can sound an alarm or bell. This system is suitable for detecting customers entering a shop or vehicles approaching a driveway. The Infrared Proximity Detector employs an infrared detector and can be integrated into various devices such as automatic door openers and burglar alarms. The circuit consists of an infrared transmitter and an infrared receiver. In the event of a power outage during darkness, a photoresistor activates an array of battery-powered white LEDs. A timer is included to turn off the LEDs after a specified duration to conserve power. The Light Pollution Meter is designed to provide visual comparisons for measuring sky brightness and light pollution.

The Dark Activated Switch or Porch Light Switch circuit is designed to function effectively in low-light conditions by utilizing a light-dependent resistor (LDR) as the primary sensor. The LDR is connected in a voltage divider configuration with a variable resistor (VR1), allowing for the adjustment of the light sensitivity threshold. When the ambient light level falls below the set threshold, the voltage across the LDR changes, triggering the activation of a relay. This relay can then control external devices such as lights or buzzers, making it suitable for applications such as porch lighting or security systems.

In addition to the dark-activated switch, the circuit includes a schematic for a light-activated relay, which operates conversely by activating the relay when light levels exceed the preset threshold. This dual functionality allows for versatile applications depending on the desired operational conditions.

The Dark Sensitive Switch is a simplified version of the dark-activated switch, focusing on the operation of the relay based solely on the light intensity detected by the LDR. This circuit is particularly useful in scenarios where automatic control of lighting is required, enhancing energy efficiency and convenience.

The Door Minder system employs an infrared beam to monitor specific areas such as entrances and passageways. The operation is based on the principle of interruption; when the infrared beam is broken, the circuit triggers a relay, which can activate an alarm or bell. This feature is beneficial for retail environments or security applications where monitoring of foot traffic is necessary.

The Infrared Proximity Detector circuit integrates both an infrared transmitter and receiver to create a detection system that can be utilized in automatic doors and burglar alarms. The interaction between the transmitter and receiver allows for the detection of objects or individuals within a defined range, enhancing security and automation in various applications.

In the event of a power outage, the circuit that turns on white LEDs is activated by a photoresistor detecting darkness. This feature ensures visibility during power failures while minimizing battery consumption through the inclusion of a timer that automatically turns off the LEDs after a designated time.

Lastly, the Light Pollution Meter serves as a valuable tool for assessing sky brightness and light pollution levels. This device is designed to provide visual comparisons, aiding in the understanding and measurement of environmental light conditions.Dark Activated Switch or Porch Light Switch This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer Dark Activated Switch This circuit will activate a relay when light falls to a preset level.

Light level can be adjusted wi th VR1 and the relay contacts may be used to operate an external light or buzzer, ORP12 photocell Dark activated relay There`s two schematics, one for light activated relay and one for dark activated relay. When the light / dark hits the sensor a relay will be activated Dark Sensitive Switch Dark Sensitive Switch is a simple project which operates a relay when the light falling on the LDR goes below a set point, LDR, pdf file Door Minder This kit uses an infrared beam to monitor door & passageways or any other area.

When the beam is broken a relay is tripped which can be used to sound a bell or alarm. Suitable for detecting customers entering a shop, cars coming up a driveway, pdf file INFRARED PROXIMITY DETECTOR This proximity detector using an infrared detector can be used in various equipment like automatic door openers and burglar alarms. The circuit primarily consists of an infrared transmitter and an infrared receiver. pdf file Light Is On When Power Is Out A loss of AC power during darkness (sensed by a photoresistor) turns on an array of battery-powered white LEDs.

To conserve power, a timer turns off the LEDs after a particular period of time Light Pollution Meter Light Pollution Meter, Notes on the design and construction of a visual comparison photometer for measuring sky brightness and light pollution 🔗 External reference