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In some circumstances a filament bulb is used as a variable resistor. As the filament heats up, its resistance increases. This effect is used in some automatic gain control circuits; as the signal level increases, the changing resistance of the bulb can modify the feedback level in order to hold the level constant.
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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.
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 happens to an LDR when a bright light is shined upon it?
When LDR is exposed to light energy . Due to light energy incident on LDR surface, free electron movement of an atom is increased in LDR. This causes high conduction of curent flowing through LDR. beause of free electron movement in LDR, resitance get decreased.
What is the function of the Light dependent resistor?
The resistance of LDR increases when light is not available (or is limited). And the resistance drops when Light is abundant.This principle can be used in proximity detectors where one or more light source(s) is/are active. When a person / object comes in proximity of the source, the light gets reflected from the object-surface & can now be received by LDR. So due to proximity of the object, resistance of LDR changes - this can be used to trigger different actions like open the door, trigger a motor. Fire an alarm. etc.Resistance of LDR varies according to intensity of incident light over it,It is used in street light to detect day/night and turn on/off the street light automatically
What is the shape of the graph between volt and electric charge where Volt is the potential difference between the ends of an ohmic resisitor and electric charge is the current flowing through it?
-- If one axis of your graph represents the current flowing through the resistor, then label it "Current", not "Electric charge". There's a big difference between charge and current. -- Ideally, the current through an ohmic resistor is a linear function of the voltage across its ends, namely a direct proportion with the resistance being the constant of proportionality. -- Ideally, the graph is a straight line, with slope equal to the resistance in ohms, and y-intercept of zero. -- In reality, the resistor dissipates energy at the rate of (voltage) x (current) watts. It must warm up as a result, and the change in its temperature always has some effect on its ohmic resistance.
What is the difference between an ohmic resistor and a non-ohmic resistor?
A non-ohmic resistor doesn't have a constant resistance. A ohmic resistor has a constant resistance.
How do you set the sensitivity of a light dependent resistor?
using a variable resistor we can adjust the sensitivity of a light dependent resistor
Is LDR an ohmic conductor?
A Light Dependent Resistor (LDR) is not considered an ohmic conductor. Ohmic conductors follow Ohm's Law, where the current through the material is directly proportional to the voltage across it, resulting in a constant resistance. In contrast, the resistance of an LDR changes with varying light intensity, leading to a non-linear relationship between voltage and current. Thus, its behavior does not conform to ohmic characteristics.
Is Light dependent resistor an example of resistor?
yes, a variable resistor
What happens to the resistance of a common ohmic resistor when it is heated?
When a common ohmic resistor is heated, its resistance typically increases.
Is a ceramic resistor ohmic?
yes
What are non ohmic devices give an example?
non ohmic devices are diodes, LED's, Thermistors, LDR(light dependent resistors, cells in series.
What is an LDR symbol?
An LDR is a Light dependent resistor.
Who invented light dependent resistor?
K. K.
In technology what does LDR stand for?
LDR stands for Light Dependent Resistor. It is a type of resistor that changes its resistance based on the amount of light that falls on it. This change in resistance allows LDRs to be used in light-sensitive applications, such as automatic lighting controls.
What is the meaning of LDR?
LDR refers to Light Dependent Resistor.
What are the advantages and disadvantages of light dependent resistor?
itroduction on LDR
