My Light 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). The circuit idea may be understood with the below mentioned points: Transistor T1 alnog with R3, C6 and the LDR itself forms a simple light sensor stage.  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.  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. 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. The above condition pers...

 Notes: As I was developing my IR Extender Circuit, I needed to find a way of measuring the relative intensities of different Infra red light sources. This circuit is the result of my research. I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET opamp, CA3140 is used in the differential mode to amplify the pulses of current from the photodiode. LED1 is an ordinary coloured led which will light when IR radiation is being received. The output of the opamp, pin 6 may be connected to a multimeter set to read DC volts. Infra red remote control strengths can be compared by the meter reading, the higher the reading, the stronger the infra red light. I aimed different remote control at the sensor from about 1 meter away when comparing results. For every microamp of current through the photodiode, about 1 volt is produced at the output. A 741 or LF351 will not work in this circuit.  Although I have used a 12 volt power supply, a 9 volt battery will also work here.

This project sprang from the need to be able to remotely control audio-visual equipment placed inside cupboards. RF-based commercial units such as those used for home theatre were found to be overkill for this application. The circuit is based on a commonly available infrared receiver module (IRX1) and a PIC12F675 microcontroller (IC1) – see circuit. Most infrared standards specify a nominal 38kHz carrier signal for data transmission, which the module receives and demodulates. Circuit diagram: Infrared Remote Extender Circuit Diagram Digital data output: The digital data output from the module is fed into GP2 (pin 5) of the PIC micro, where it’s received by the PIC program and duplicated on output GP1 (pin 6). This flashes the "Signal" LED to give a visual indication that the extender is receiving the remote control’s transmissions. Copyright: Silicon Chip Magazine