Chapter 10 Photoresistor & LED
=====================================
In this chapter, we will learn how to use a photoresistor.

Project 10.1 NightLamp
------------------------

A photoresistor is very sensitive to the amount of light present. We can take 
advantage of the characteristic to make a nightlight with the following function: 
when the ambient light is less (darker environment) the LED will automatically 
become brighter to compensate and when the ambient light is greater (brighter environment) 
the LED will automatically dim to compensate.

Component List
^^^^^^^^^^^^^^^
- ESP32-S3-WROOM x1
- GPIO Extension Board x1
- 830 Tie-Points Breadboard x1
- Resistor 10kΩ  x1
- Resistor 220Ω  x1
- Photoresistor x1
- LED x1
- Jumper Wire x4

Component knowledge
^^^^^^^^^^^^^^^^^^^^
:ref:`Photoresistor <cpn_photoresistor>`
"""""""""""""""""""""""""""""""""""""""""""


Connect
^^^^^^^^^^^^
The circuit of this project is similar to project Soft Light. The only difference 
is that the input signal is changed from a potentiometer to a combination of a 
photoresistor and a resistor.

.. image:: img/connect/10.png

Code
^^^^^^^
Move the program folder “Basic_Starter_Kit_for_ESP32_S3/Python/Python_C
odes” to disk(D) in advance with the path of “D:/Micropython_Codes”. 
Codes of this project is logically the same as the project Soft Light. 

**10.1_Nightlamp**

.. image:: img/software/10.1.png

Click “Run current script”. Cover the photoresistor with your hands or illuminate 
it with lights, the brightness of LEDs will change.

The following is the program code:

.. code-block:: python

    from machine import Pin,PWM,ADC
    import time

    pwm =PWM(Pin(14,Pin.OUT),1000)
    adc=ADC(Pin(1))
    adc.atten(ADC.ATTN_11DB)
    adc.width(ADC.WIDTH_12BIT)

    def remap(value,oldMin,oldMax,newMin,newMax):
        return int((value)*(newMax-newMin)/(oldMax-oldMin))

    try:
        while True:
            adcValue=adc.read()
            pwmValue=remap(adcValue,0,4095,0,1023)
            pwm.duty(pwmValue)
            print(adcValue,pwmValue)
            time.sleep_ms(100)
    except:
        pwm.deinit()

In this code, we use ADC to read the ADC value of the photoresist and map it to 
the PWM of the control LED, so that the brightness of the LED can change accordi
ngly with the change of the ambient light intensity.