LBL Activated Remote Control Circuit Diagram

This is the simple Laser Beam Light Activated Remote Control Circuit Diagram. 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).

 LBL Activated Remote Control Circuit Diagram

The circuit idea may be understood with the below mentioned points:

1. Transistor T1 alnog with R3, C6 and the LDR itself forms a simple light sensor stage.
2. The LDR is connected across the base of the transistor and the positive supply such that when light falls over the LDR, T1 receives the required base bias and conducts.
3. When T1 conducts, the high potential at pin 14 of IC1 is pulled to logic low. However since a logic low wouldn't effect pin#14, IC1 does not respond as yet.
4. 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 it's output from pin#3 to pin#2. This makes pin#3 logic low, activating T2, and the preceding relay driver stage.
5. The above condition persists until the LDR is illuminated again with a flashlight or with a laser beam.
6. The above operation alternately toggles the output ON and OFF providing the required toggling actions to the connected load.
7. The LDR must be covered inside an opaque pipe, about an inch long so that the ambient light stays obstructed from the LDR.
8. The angle of the pipe should be kept in a such a way that it facilitates easy focusing of the light beam toward the LDR.
9. C6 ensures that the system does not respond to accidental spurious light beams in case it finds its way inside the pipe, and over the LDR.

Parts List

• R3,R4,R5,R6,R7 = 2K2
• T1 = BC547,
• T2 = BC557
• IC1 = 4017
• IC2 = 7812
• ALL DIODES = 1N4007
• C6,C7 = 10uF/25V
• C8 = 1000uF/25V
• C10 = 0.1uF