Description
LDR Module – Light Dependent Resistor – LM393 LDR’s resistance is very high in the darkness, almost as high as 1MΩ but when there is light that falls on the LDR, the resistance falls down to a few K (10-20KΩ @ 10 lux, 2-4K @ 100 lux) depending on the model.
The LDR module produces an output voltage according to the resistance of the LDR and is made available at Analog Output (AO) pin. The same signal is fed to an LM393 High Precision Comparator to digitize it and is made available at a Digital Output (DO) pin. The module has a built-in potentiometer for sensitivity adjustment of the digital output (DO).
You can set a threshold by using a potentiometer; So that when the incident light level on the LDR exceeds the threshold value, the module will output LOW otherwise HIGH. Apart from this, the module has two LEDs. The Power LED will light up when the module is powered. The Status LED will light up when the digital output goes LOW.
Features: ADIY LDR Module
- LM393-based design.
- It can detect ambient brightness and light intensity.
- Adjustable sensitivity (via blue digital potentiometer adjustment).
- Output Digital – 0V to 5V, Adjustable trigger level from preset.
- LEDs indicating output and power.
- Mounting hole
- Power and Signal indicator LED
- Analog and Digital Out
- Adjustable threshold (via potentiometer)
- Input Voltage (V): 3.3 to 5
Specification: LDR Module
- Maximum power dissipation is 200mW
- The maximum voltage at 0 lux is 200V
- The peak wavelength is 600nm
- The minimum resistance at 10lux is 1.8kΩ
- Maximum resistance at 10lux is 4.5kΩ
- Typical resistance at100lux is 0.7kΩ
- Dark resistance after 1 sec is 0.03MΩ
- Dark resistance after 5 sec is 0.25MΩ
Advantages: LDR Module
- Sensitivity is High
- Simple & Small devices
- Easily used
- Inexpensive
- There is no union potential.
- The light-dark resistance ratio is high.
- Its connection is simple
Applications:LDR Module
- Light sensitive devices
- Light intensity meter
- Burglar alarm circuit
How LDR Module works:
First of all, we need to connect the LDR sensor module to a 5v power supply. Then set the threshold voltage at the Non-Inverting input of the IC according to the present light intensity by rotating the preset knob for setting the sensor sensitivity.
When light intensity increase on the surface of the LDR then the resistance of the LDR decreases. Then the maximum amount of voltage will be allocated across the resistor. So, a Low amount of voltage from the LDR is given to the Inverting input of the IC. Then the Comparator IC compares this voltage with the threshold voltage. In this condition, this input voltage is less than the
the threshold voltage, so the sensor output goes LOW.
the threshold voltage, so the sensor output goes LOW.
In contrast, when light intensity decrease (low/dark) on the surface of the LDR then the resistance of the LDR increases. Then the maximum amount of voltage will be allocated across the LDR. So, a High amount of voltage from the LDR is given to the Inverting input of the IC. Then the Comparator IC compares this voltage with the threshold voltage. In this condition, this input voltage is greater than the threshold voltage, so the sensor output goes high.
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