led photo sensor circuit

Description: This design outlines a sensor circuit that utilizes an LED as a light sensor. The operational control and amplification of the output are managed by a 1458 integrated circuit (IC), which functions as an operational amplifier (op-amp). The circuit exploits the photovoltaic voltage generated by a standard LED. The voltage from the LED is buffered by a junction field-effect transistor (JFET) and subsequently fed into the inverting input of the op-amp, configured with a gain of approximately 20. This configuration results in an output voltage change of about 5 volts when transitioning from darkness to bright light. A 100K potentiometer is used to adjust the output voltage, setting it to around 7 volts in darkness and decreasing to approximately 2 volts in bright light.

The sensor circuit operates by leveraging the unique properties of an LED, which can generate a small voltage when exposed to light. This photovoltaic effect is harnessed to detect varying light levels. The JFET serves as a buffer, isolating the LED from the op-amp input to prevent loading effects that could distort the signal.

The 1458 op-amp amplifies the buffered voltage signal, effectively increasing its magnitude to a more usable level. The gain of the op-amp is set to approximately 20, which means that for every 1 volt change at the input, there will be a corresponding 20 volts change at the output. This gain is crucial for applications where significant voltage swings are necessary to trigger subsequent electronic components or systems.

The inclusion of a 100K potentiometer allows for fine-tuning of the output voltage. In complete darkness, the output can be adjusted to reach around 7 volts, providing a clear indication of low light conditions. As ambient light increases, the output voltage drops, reaching about 2 volts in bright light. This range of output voltages can be utilized to interface with other circuits, such as microcontrollers, for further processing or control actions.

Overall, this sensor circuit design provides a robust solution for light detection applications, combining simple components to achieve effective light sensing capabilities with adjustable output levels.This is a design for sensor circuit. This circuit is using LED for sensor a light. But, for control operation and amplifier the output is using 1458 IC. This is an op-amp. This is the figure of the circuit; A circuit that is takes advantage of the photo-voltaic voltage of an ordinary LED. The LED voltage is buffered by a junction FET transistor an d then applied to the inverting input of an op-amp with a gain of about 20. This produces a change of about 5 volts at the output from darkness to bright light. The 100K potentiometer can be set so that the output is around 7 volts in darkness and falls to about 2 volts in bright light.