The sunset to sunrise lighting switch is an application of light sensor circuit that is designed to control the automatically based on the light illuminated on the LDR light sensor. The light sensor circuit can be used to design various practical embedded systems based sensor based projects such as security alarm system by photo electric sensor, Arduino managed high sensitive LDR based power saver for street light control system, a solar highway lighting system with auto turn off in daytime, sunset to sunrise lighting switch, and so on. Practical Applications of Light Sensor Circuit As the Darlington pair is activated, the relay coil gets enough supply to get energized, and hence, the load is switched on during night time or when no light is illuminated on LDR. Now, the current flows through the low-resistance path such that it increases base voltage of Darlington pair to reach more than 1.4v. Thus, due to very high resistance of LDR the current flow is very less or almost zero like an open circuit condition. Similarly, during the night time (when the light illuminated on LDR is very less), the LDR resistance increases to a very high value of around a few Mega ohms (approximately 20MΩ). Hence, the load is switched off during the daylight. Thus, the relay coil does not get enough supply to get energized. We are aware of the principle of current, that the current always flow in the low resistance path. This is due to the fact that the resistance offered by the LDR during daytime or when the light is illuminated on LDR is less compared to the resistance of the remaining part of the circuit (that is through relay and Darlington pair). Thus, the supply passes through the LDR and ground through the resistor and variable resistor as shown in the light sensor circuit. A 230v AC supply for both the load and the bridge rectifier is to be maintained continuously for uninterrupted operation of the light sensor circuit.ĭuring the daytime, the light sensor LDR has very-low resistance of around a few 100Ω. The IC7806 DC voltage regulator is used to convert the 12v DC into 6v DC, and then, this 6V DC is supplied to the circuit. The diodes connected in the form of a bridge are used to convert the 12v AC into 12v DC. The bridge rectifier circuit utilizes a step-down transformer to step-down the 230v into 12v. This bridge rectifier circuit converts the 230v AC supply into a 6v DC. The DC voltage required by the light sensor circuit is supplied from a battery or by using a bridge rectifier circuit.
A 230v AC supply is provided to the load (in this case, the load is represented with a lamp). The light sensor circuit is an electronic circuit designed using (light sensor) LDR, Darlington pair, relay, diode, and resistors which are connected as shown in the light sensor circuit diagram. Generally, the relay consists of a coil, this coil gets energized whenever it gets enough supply (required amount of supply depends on the rating of the relay). These LDR sensors are passive and doesn’t produce any electrical energy. But, LDR (Light Dependent Resistor or photoresistor) is used as a light sensor in this light sensor circuit. There are different types of light sensors available such as photoresistors, photodiodes, photovoltaic cells, phototubes, photomultiplier tubes, phototransistors, charge coupled devices, and so on. To understand the working operation of the light sensor circuit, we must know a brief about the components used in designing the light sensor circuit.
The light sensor circuit consists of major electrical and electronic components such as light sensor, Darlington pair, and relay.
DLIGHT SENSOR MANUAL
The light sensor circuit helps to evade the manual control of the street lights erected on highways which is risky and also causes wastage of power. Hence, we can describe it as an automatic light sensor. By using this light sensor circuit, we can eliminate manual switching as the loads can be controlled automatically based on the daylight intensity. The light sensor circuit is a simple electrical circuit, which can be used to control the (switch on and off) electrical load appliances like lights, fans, coolers, air conditioners, street lights, etc., automatically.
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