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Questions and Answers
What is another common name for a light dependent resistor?
What is another common name for a light dependent resistor?
How does the resistance of an LDR change as light intensity increases?
How does the resistance of an LDR change as light intensity increases?
What type of material is primarily used in manufacturing LDRs?
What type of material is primarily used in manufacturing LDRs?
Which characteristic is associated with placing an LDR in complete darkness?
Which characteristic is associated with placing an LDR in complete darkness?
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Which of the following applications commonly use Light Dependent Resistors?
Which of the following applications commonly use Light Dependent Resistors?
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What is a notable disadvantage of using LDRs?
What is a notable disadvantage of using LDRs?
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Within the context of fire alarms, what is the role of the LDR?
Within the context of fire alarms, what is the role of the LDR?
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What does it mean that LDRs are considered to be non-linear devices?
What does it mean that LDRs are considered to be non-linear devices?
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Study Notes
Robotics 2 - Lesson 2: Light Dependent Resistor
- This lesson covers light dependent resistors (LDRs), also known as photoresistors or photocells
- LDRs are variable resistors controlled by light
- Their resistance changes based on light intensity
Target
- Students should be able to define LDRs
- Students should be able to identify the working principle and characteristics of LDRs
- Students should be able to create projects utilizing LDRs
Light Dependent Resistor (LDR) Characteristics
- LDRs are made of semiconductor materials with high resistance
- LDRs are non-linear devices
- The sensitivity of LDRs varies with the wavelength of incident light
- Some photocells may not respond to certain wavelengths
Applications of LDR
- LDRs are used in various devices, such as automatic streetlights, camera light sensors, and solar panels
- LDRs enable automatic light detection and contribute to energy-saving applications
- Light sensors utilizing LDRs activate LEDs when sufficient light reaches the LDR
- Fire alarms use LDRs to detect smoke by sensing the change in light intensity caused by smoke
- Automatic streetlights use LDRs; they turn on at night and off during the day
LDR Characteristics: Photoconductivity
- As light intensity increases, LDR resistance decreases
- LDR resistance is very high when kept in the dark. This is known as dark resistance
- Dark resistance can be as high as 1012 Ohms
LDR Advantages
- LDRs are inexpensive and readily available in various sizes and shapes
- They require minimal power and voltage for operation
LDR Disadvantages
- They are relatively inaccurate
- Response time of about tens or hundreds of milliseconds
Activity 2: Light Dependent Resistor
- The activity involves building and coding a circuit with an LDR and an LED to react to light changes
Target - Activity 2
- Students at the end of this part should be able to build and input code to their systems based on provided circuit diagrams
Materials - Activity 2:
- The presentation displays images of components, indicating various materials required for the activity (e.g. Arduino board, resistors, wires, LDR).
Code for Activity 2: Light Dependant Resistor
- The presentation contains Arduino code for the activity
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Description
This lesson focuses on Light Dependent Resistors (LDRs), which are variable resistors sensitive to light. Students will learn about the characteristics, working principles, and practical applications of LDRs in projects. By the end, you will be able to define LDRs and utilize them effectively.
