# LDR output values

For the plant monitoring system, i have got the output values as 40,56,75,50, etc., after placing it in both dark and light conditions. What do these values actually mean, how is it calculated and in what unit? I have attached a picture for reference.

Hi @pritichha15,

For the plant monitoring system, the output values (e.g., 40, 56, 75, 50, etc.) obtained in both dark and light conditions represent the analog readings from the Light Dependent Resistor (LDR) used in the setup. These values indicate the resistance of the LDR, and the relationship between LDR resistance and light intensity is inversely proportional, meaning the resistance decreases as the intensity of light increases.

The connection details for the hardware are as follows:

Hardware Required:

• 1 x Bolt IoT Module
• 1 x Micro USB Cable
• 1 x LDR (2-legged device with a red wave pattern disk on top)
• 1 x 10k Ohm Resistor (brown black orange color code)

Connection Steps:

1. Insert one lead of the LDR into the Bolt Module’s 3v3 Pin.
2. Insert the other lead of the LDR into the A0 pin.
3. Insert one leg of the 10k Ohm resistor into the GND pin.
4. Insert the other leg of the resistor into the A0 pin.

The resistance of the LDR is measured by the Bolt IoT Module, and the obtained analog values are indicative of the light conditions. The exact unit of these values depends on the scale used in the system but typically ranges between 0 and 1023 for analog readings. A higher value signifies higher light intensity, while a lower value indicates lower light intensity.

Hello @pritichha15 ,
Concept is that when the light intensity increases LDR resistance decreases and the value of the reading increases , and vice versa. The unit used is Lux(luminous intensity).
Maximum reading is 1.02 thousand(very bright) Lux and minimum is 0(very dark).
I think the mistake you are making is that you should give adequate time(atleast 2 minutes) between two successive readings to note changes in the value for bright and dark condition.
I hope it helps