Laser Beam Light Activated Remote Control Circuit

Description: The following post illustrates a simple light-operated remote control circuit that can be activated by an ordinary flashlight or, more effectively, through a laser beam unit (keychain type). The Light Dependent Resistor (LDR) is connected between the base of the transistor and the positive supply, such that when light falls on the LDR, transistor T1 receives the necessary base bias and conducts. When T1 conducts, the high potential at pin 14 of integrated circuit IC1 is pulled to logic low. However, since a logic low does not affect pin 14, IC1 does not respond immediately. The moment the light on the LDR is turned off, T1 switches off, and pin 14 receives a logic high via resistor R5. At this point, IC1 responds and shifts its output from pin 3 to pin 2, causing pin 3 to go logic low, which activates transistor T2 and the preceding relay driver stage.

This light-operated remote control circuit utilizes a Light Dependent Resistor (LDR) as a sensor to detect light changes. The circuit operates by leveraging the properties of a transistor (T1) and an integrated circuit (IC1) to control the output based on light exposure. The LDR is critical in determining the state of T1, which acts as a switch in the circuit.

When the circuit is powered, the LDR will conduct current when exposed to light, allowing T1 to turn on. This state pulls pin 14 of IC1 to a low logic level, but the IC remains inactive because it does not respond to this condition. The circuit is designed to respond to the cessation of light; thus, when the light source is removed, T1 turns off, and the voltage at pin 14 of IC1 is restored to a high logic level through resistor R5.

The transition of pin 14 from low to high triggers a change in the output state of IC1. This response is critical as it shifts the output from pin 3 to pin 2. The logic low at pin 3 activates transistor T2, which then controls the relay driver stage. This relay driver stage can be used to control larger loads, effectively allowing the circuit to operate various devices remotely with the simple act of toggling a light source.

The design emphasizes simplicity and effectiveness, making it suitable for applications where wireless control is needed, such as in home automation or remote switching of devices. The use of a laser beam for activation provides a more precise control method compared to traditional light sources, enhancing the circuit's utility in various scenarios.The following post illustrates a simple light toggled/operated remote control circuit, which can be activated by an ordinary flashlight or more effectively through a laser beam unit (key chain type). The LDR is connected across the base of thetransistor and the positive supply such that when light falls over the LDR, T1 receives the required base

bias and conducts. When T1 conducts, the high potential at pin 14 of IC1 is pulled to logic low. However since a logic low wouldnt effect pin#14, IC1 does not respond as yet. The moment light on the LDR is switched OFF, T1 is switched OFF and pin#14 now instantly receives a subsequent logic high via R5. now IC1 responds, and shifts its output from pin#3 to pin#2. This makes pin#3 logic low, activating T2, and the preceding relay driver stage.