What do the readings under variable ‘light’ represent and how do they vary with the intensity of light?
(aren’t the values supposed to drop when the product is kept in improperly lit rooms or dark surroundings?)
The column you specified is showing the values that your LDR sensor is reading.
Yes, the values do change when the sensor is placed in different lighting conditions.
LDR’s resistance decreases as the light intensity increases. In the dark and at low light levels, the resistance of an LDR is high and little current can flow through it. When the light level decreases, the resistance of the LDR increases.
In bright light, the resistance of an LDR is low and more current can flow through it.
Hope it helps in addressing your doubt:)
Hello, @itsmejeet16! To be more precise and technical, the values under the column titled ‘light’ represent the decimal equivalent of the digital value of the voltage across resistor R2. Let me elaborate on it for you. At the heart of the Bolt WiFi Module, we have the Tensilica Xtensa 32-bit LX106 RISC microprocessor. It has a 10-bit precision SAR ADC whose input pin is available on Bolt WiFi Module as A0 and, the input voltage range of ADC is 0-1V.
So, when the input voltage is minimum that is 0V, ADC outputs a binary value 0000000000, which is equivalent to 0 in the Decimal number system. Similarly, when the input voltage is maximum that is 1V, ADC outputs a binary value 1111111111, which is equivalent to 1023 in the Decimal number system. Since the pin A0 is 3.3V tolerable, the ADC continues to output 1023 if the input voltage goes beyond 1V.
In our case, the values under the column titled ‘light’ are just the Decimal equivalents of raw ADC data. You can verify this yourself if you have a preset or a potentiometer and a multimeter. I just did it to be able to answer your query in depth. The formula to obtain ADC value is:
value= Vin/Vin(max) ×1023
where, Vin is the input to ADC that is voltage across resistor R2.
Now let’s discuss how these values vary with the intensity of light. For higher light intensity, the resistance of LDR will be lower. Consequently, the voltage across R2 will increase and, the ADC values will rise tending towards 1023. Similarly, for lower light intensity, the resistance of LDR will be higher. Consequently, the voltage across R2 will decrease and, the ADC values will fall tending towards 0. Hope you find this informative…
yes Light Column shows the readings taken by LDR sensor.If yoy change Intensity of Light then reading also changes.
If You placed sensor in Room which dont have Light then it gives Low number of readings in the graph as intensity Is inversely Proportional to Resistance .
and wiceversa for room which have more light so it will gives higher values 1.2 thousand in the graph.
you may check it.
Readings under the ‘light’ variable represents the intensity of light as measured by the LDR(light dependent resistor) sensor. As mentioned in the lecture videos LDR’s resistance is inversely proportional to the light intensity i.e., if the LDR is in dark surroundings then its resistance is high and the current drawn will be less and also the voltage across the LDR is less.(from voltage divider rule and ohms law).
Yes, the values under the light column will drop when our plant monitoring device is kept in dark surroundings.
To answer your doubt, yes here we are observing the readings of the LDR over a certain duration of time. The values under the variable “light” are the light intensity readings taken by the LDR at different instants of time. Also, the readings do change with respect to the brightness of the room. Sometimes you just have to wait longer to notice the change. As elaborated in the lectures, LDR has a unique, rather very useful property in the field of electronics i.e., its resistance is inversely proportional to the intensity of the incident light which makes a LDR similar to a variable switch in its respective circuit.
I would also suggest you to use a graph rather than a table which would help in better analysis. Nothing is wrong in this table format though; you can analyze the data from here also but it’s just that a graph is a better way of representation.
Hope my answer is helpful…