Dark Sensor Circuit

Here’s a design for simple dark sensor circuit that can be connected as an input or switch to another circuit. The sensor has three green wires (1, 2 and 3). Wire 2 should always be connected to one of the inputs. If wire 1 is also connected then the sensor acts as a dark sensor. If wires 2 and 3 are connected to the inputs then sensor operates as a light sensor. This is the figure of the circuit;

All circuits are drawn on software such as Crocodile Clips. Using this software the individual components can be joined together on the screen. Once the circuit is drawn its operation can be simulated to see if it works. If it fails it can be corrected on the computer screen and tested again. Using software to test circuit designs saves time as there is no need to physically solder together components. It also saves money as components and materials are not wasted on failed circuits.

Photocell Sensor Circuit

Photocell sensor can be regarded as a transducer that is used to detect the light intensity. At full intensity beam with a photocell resistance could be worth about 10 Ohm and the low intensity light (in darkness) could be worth several hundred Ohm. This is the figure circuit of the basic photocell sensor circuit;

 

This circuit using a Cadmium Sulfide (Cds) photocell sensor. The workings of this photocell sensor circuit, when the light falling on the photocell (PC1) is blocked, the resistance will increase and the voltage on the PC1 will rise. When the voltage rises above half of the supply voltage, the output of the comparator will turn on and the LED will light. Because of wide variation in CdS photocells is usually best to install the cell and then measure the resistance under normal lighting conditions. A resistor with a value of approximately three to five times the cell resistance measured is then selected for R1. For example, if the cell resistance was measured at 400 ohms then from 1200 to 2200 ohm resistor is used.

Increasing the value of R1 will cause the sensitivity of the photocell sensor decreases. This may be required when the light that falls on these cells is not too strong or shadows can affect the photocell.

LM741 Light Dark Sensor Circuit

This is a design for dark light sensing circuit. Here’s the figure of the schematic circuit;

Function: extremely useful and versatile in a wide range of renewable energy projects from automatic lighting to security systems. Component: Transistor, Potentiometer, Capacitor, Relay, LDR, LED Spotlight.

TL071 JFET Light Sensor Circuit

This is a design circuit for light sensing circuit. Here is the schematic figure circuit;

Above picture shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. Component: TL071 IC, Resistor, Diode.

Photo Sensor Circuit For Street Light

This is a design circuit for Photo Sensor Circuit Diagram For Street Light Electronic. This circuit using the 2N3906 Transistor. Here is the figure of the circuit diagram;

Features: lower value for the 7.5K resistor, common emitter resistor for positive feedback, be adjusted to about half the supply, 8 volts and 4 volts switching points. Component: Transistor, Resistor, Diode, Relay.