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Q: What is the need of preset resistor in ldr circuit?
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What is the principle of operation of LDR?

Working of light dependent resistor This circuit explains the principle of operation of LDR (light dependence resistor). The circuit has various applications like shadow alarm, automatic night/morning lamp. LDR, an acronym for light dependent resistor is a resistor whose resistance is dependent on light. The resistance of LDR is of the order of Mega Ohms in the absence of light and reduces to a few ohms in presence of light. In this circuit when the light falls on LDR, the resistance of LDR becomes low and the entire voltage drop takes place across the variable resistance VR1 (10K). As a result the base of transistor (T1) gets high input and it gets biased thereby glowing the LED. When no light falls on LDR, the resistance of LDR becomes high so almost entire voltage drop takes place across it and the base of transistor is at low potential. So transistor does not gets biased nor it becomes conducting, hence switching off the LED. The sensitivity of the circuit can be adjusted by varying the preset VR1. LDR, an acronym for light dependent resistor is a resistor whose resistance is dependent on light. The resistance of LDR is of the order of Mega Ohms in the absence of light and reduces to a few ohms in presence of light. In this circuit when the light falls on LDR, the resistance of LDR becomes low and the entire voltage drop takes place across the variable resistance VR1 (10K). As a result the base of transistor (T1) gets high input and it gets biased thereby glowing the LED. When no light falls on LDR, the resistance of LDR becomes high so almost entire voltage drop takes place across it and the base of transistor is at low potential. So transistor does not gets biased nor it becomes conducting, hence switching off the LED. The sensitivity of the circuit can be adjusted by varying the preset VR1.


What is an LDR symbol?

An LDR is a Light dependent resistor.


What is the meaning of LDR?

LDR refers to Light Dependent Resistor.


What does LDR stand for?

Light Dependent Resistor LDR also means long distance relationship.


It is the ldr is type of resistor?

No i dont think so!


In technology what does LDR stand for?

Light dependent resistor.


What is a use of a ldr?

its a light dependant resistor xx


What are the advantages and disadvantages of light dependent resistor?

itroduction on LDR


What is the purpose of LDR on a circuit?

158980


How do you make Light-dependent- resistance circuit?

A Light Dependent Resistor (aka LDR, photoconductor, or photocell) is a device which has a resistance which varies according to the amount of light falling on its surface.A typical light dependent resistor is pictured above together with (on the right hand side) its circuit diagram symbol. Different LDR's have different specifications, however the LDR's we sell in the REUK Shop are fairly standard and have a resistance in total darkness of 1 MOhm, and a resistance of a couple of kOhm in bright light (10-20kOhm @ 10 lux, 2-4kOhm @ 100 lux).Uses for Light Dependent ResistorsLight dependent resistors are a vital component in any electric circuit which is to be turned on and off automatically according to the level of ambient light - for example, solar powered garden lights, and night security lighting. An LDR can even be used in a simple remote control circuit using the backlight of a mobile phone to turn on a device - call the mobile from anywhere in the world, it lights up the LDR, and lighting (or a garden sprinkler) can be turned on remotely!Light Dependent Resistor CircuitsThere are two basic circuits using light dependent resistors- the first is activated by darkness, the second is activated by light. The two circuits are very similar and just require an LDR, some standard resistors, a variable resistor (aka potentiometer), and any small signal transistor In the circuit diagram above, the LED lights up whenever the LDR is in darkness. The 10K variable resistor is used to fine-tune the level of darkness required before the LED lights up. The 10K standard resistor can be changed as required to achieve the desired effect, although any replacement must be at least 1Kto protect the transistor from being damaged by excessive current.By swapping the LDR over with the 10K and 10K variable resistors (as shown above), the circuit will be activated instead by light. Whenever sufficient light falls on the LDR (manually fine-tuned using the 10K variable resistor), the LED will light up.Using an LDR in the Real WorldThe circuits shown above are not practically useful. In a real world circuit, the LED (and resistor) between the positive voltage input (Vin) and the collector (C) of the transistor would be replaced with the device to be powered. Typically a relay is used - particularly when the low voltage light detecting circuit is used to switch on (or off) a 240V mains powered device. A diagram of that part of the circuit is shown above. When darkness falls (if the LDR circuit is configured that way around), the relay is triggered and the 240V device - for example a security light - switches on.NEW For details of a more advanced light/dark sensor circuit click here to read our new article LM741 Light/Dark Sensor Circuit. We have these circuits available for sale.


What is a LDR dependent AC dimmer?

The LDR dependent AC dimmer is a Light Dependent Resistor which works by chopping off the parts of the AC voltage.


What is Light dependence resistor?

A LDR or light dependant resistor is a resistor that works when light is not shining on it, so if there is light on it it will not resist a current, you can also get them to work the other way.