how to use a photoresistor or light-dependent resistor (LDR)

[rajbadri]

hi
is it possible to use a photoresistor or light-dependent resistor (LDR) in esp easy
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please guide

Thanks

[costo]

is it possible to use a photoresistor or light-dependent resistor (LDR) in esp easy

Yes it is possible to set up a circuit in which a Light Dependant Resistor is used, but it will not give you the resistance in ohms, it will give you a certain voltage on the 'Analog Input' which is more or less dependent by the quantity of light that is at your LDR.
You have to put a resistor in series with the LDR and measure the voltage over the LDR. The value of this resistor depends on the LDR-type and if you are using ESP or NodeMCU. A good value to start experiment with may be 100 kiloohms.

But if you only want to measure the quantity of light it is so much easyer to use a BH1750 Lux module.

[jack2222]

Hello,
How can I do if I want to capture the signal from 2 (or 4) photoresistor, to compare the strenght between them ? (e.g. for a solar tracker)

Thanks for your kind support!

[TD-er]

You can use some external ADC chip which has several inputs.
We have support for several in ESPEasy.

[Ath]

Many moons ago, I experimented with 'aiming for the light' too, and built me this, now disassembled, tiny rig:

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(Dismantled it for easier storage)

It consists of 3 TSL2561 I2C light sensors (3 only as they can be configured for 3 different addresses), 2 mini stepper motors, a few pieces of cardboard and a couple of (empty) toilet paper rolls. And not to forget, some ducttape
You will need an ESPEasy release with 'test' in its name as the plugin for the TSL2561 is available in these builds only.

Never got the rules just right, but that was probably also somewhat accountable on the state of ESPEasy in those days (mid 2018 I think), and largely on my lack of knowledge of rules at that time. Eventually I lost interest, but as the hardware works fine, I might try my luck/skills again, somewhere in the near future