ESP32-S3 board
The brain that runs your uploaded sketch.
01 First, know the pieces
What you need
Seven things, one of them new. Tap Define on any part you haven't met — the answer opens as a field note you can read and dismiss without losing your place.
GPIO extension board
Spreads the pins into rows you can reach and label.
Photoresistor
Today's sensor — its resistance follows the light falling on it.
LED
The lamp itself — it only works one way round.
220 Ω resistor
Sits in series with the LED to keep the current gentle.
10 kΩ resistor
Pairs with the photoresistor to turn light into a readable voltage.
4 jumper wires
Temporary, solder-free connections.
02 Make the physical circuit
Chart the circuit
The official Freenove diagram is your chart — schematic on top, the same circuit built on a breadboard below. Click it to enlarge. Two small circuits share the board today: the divider that reads the light, and the LED that answers it.
10 kΩ resistor
→3.3V and the divider midpoint
The fixed top half of the voltage divider.
Photoresistor
→divider midpoint and GND
Its light-driven resistance sets the midpoint voltage.
Divider midpoint
→GPIO 1
The ADC reads the light level here.
LED long leg (+)
→GPIO 14 via 220 Ω
This pin sets the lamp's brightness with PWM.
LED short leg (−)
→GND
Completes the LED's path back to zero volts.
Mind the LED's legs. The LED only lights one way round — long leg toward GPIO 14 through the 220 Ω resistor, short leg to ground. The photoresistor has no polarity, so either leg can face either way. Unplug USB before you move any wire.
03 One action at a time
Build it
This is the main path — you can finish the day without opening a single field note. Tap each step as you go to keep your place.
0 / 9 done
Seat the ESP32-S3 on the GPIO extension board and keep USB unplugged while you wire.
Place the photoresistor on the breadboard — its two legs are interchangeable.
Run the 10 kΩ resistor from the 3.3V rail to one leg of the photoresistor, and take the photoresistor's other leg to GND.
Wire the point where the resistor and the photoresistor meet — the divider's midpoint — to GPIO 1.
Place the LED so its long leg (+) heads toward GPIO 14 and its short leg (−) toward ground.
Put the 220 Ω resistor in series between GPIO 14 and the LED's long leg.
Compare every wire to the chart before you plug in USB.
Open
Sketch_11.1_NightLamp.inoin Arduino IDE and upload it.Cup a hand over the photoresistor, then light it with a phone torch — watch the LED answer each move.
04 Read just enough code
Read the code
The whole sketch is five working lines. One line in setup attaches the LED pin to a PWM channel; the loop reads the light and maps it straight onto the lamp's brightness. Switch to MicroPython if you'd rather see the same idea in Python — the wiring never changes.
#define PIN_ANALOG_IN 1
#define PIN_LED 14
#define CHAN 0
#define LIGHT_MIN 372
#define LIGHT_MAX 2048
void setup() {
ledcAttachChannel(PIN_LED, 1000, 12, CHAN);
}
void loop() {
int adcVal = analogRead(PIN_ANALOG_IN); //read adc
int pwmVal = map(constrain(adcVal, LIGHT_MIN, LIGHT_MAX), LIGHT_MIN, LIGHT_MAX, 0, 4095); // adcVal re-map to pwmVal
ledcWrite(PIN_LED, pwmVal); // set the pulse width.
delay(10);
}analogRead(PIN_ANALOG_IN)Reads the divider's midpoint voltage on GPIO 1 as a number from 0 to 4095. constrain(adcVal, LIGHT_MIN, LIGHT_MAX)Fences the reading inside the 372–2048 window before map stretches that window across the full brightness scale — this is where constrain earns its keep. ledcWrite(PIN_LED, pwmVal)Sets the lamp's brightness on GPIO 14 — 0 is dark and 4095 is full. Optional side path · same circuit
pwm =PWM(Pin(14,Pin.OUT),1000)
adc=ADC(Pin(1))
adc.atten(ADC.ATTN_11DB)
adc.width(ADC.WIDTH_12BIT)
adcValue=adc.read()
pwmValue=remap(adcValue,0,4095,0,1023)
pwm.duty(pwmValue)
print(adcValue,pwmValue)adc.atten(ADC.ATTN_11DB)Widens the ADC's range so it can read the divider all the way up to 3.3V.remap(adcValue,0,4095,0,1023)Stretches the full 12-bit reading onto MicroPython's 10-bit duty scale — the same map idea with different numbers.Same pins, same wiring. This version maps the whole 0–4095 range straight onto a 10-bit duty, so its response curve is gentler than Arduino's constrained window — the idea is identical. Run it in Thonny if MicroPython is set up; otherwise skip it — it should never block the Arduino-first path.
05 Understand, don't memorise
Four small conversions
The whole day is one chain of four conversions, each small enough to hold in your head, running many times a second.
Resistance shifts
The photoresistor's resistance follows the light falling on it.
Volts at the midpoint
The 10 kΩ divider turns that resistance into a voltage on GPIO 1.
ADC to a number
analogRead measures the voltage as a value from 0 to 4095.
Map to brightness
constrain and map squeeze the reading into a PWM level for the LED.
The chain
light → resistance → voltage → number → brightness
Why the window is 372 to 2048
A room rarely swings the ADC across its whole range. constrain fences the reading inside a realistic window, and map stretches that window over the full 0–4095 brightness scale, so the lamp spends all its range on light levels your room actually produces.
What the 10 kΩ resistor is doing
On its own the photoresistor only changes resistance, which a pin can't read directly. Paired with a fixed resistor it forms a divider, and the midpoint voltage rises and falls with the light — exactly the kind of signal the ADC measures.
06 Know it worked
Test & debug
Nothing prints to the screen today — the proof is the lamp answering your hand.
What you should see
- After upload the LED settles at a brightness set by the room's light.
- Cup a hand over the photoresistor — the brightness slides one way.
- Shine a phone torch on the sensor — the brightness slides back the other way.
Which direction is which follows how the divider sits on your board — the proof is the slide itself, steady and repeatable each time you cover and light the sensor.
If it doesn't
- LED never changes? Check the photoresistor's legs and that the divider's midpoint wires to GPIO 1.
- LED always at full? The divider is likely on the wrong rail — confirm the 10 kΩ goes to 3.3V and the photoresistor's far leg to GND.
- Nothing lights at all? Check the LED's direction and the 220 Ω resistor on GPIO 14.
- Upload fails? Swap in a data-capable USB cable.
07 Make the idea yours
Try this: make it your room's lamp
Same working circuit, two edits to the numbers. It fits inside today's 25 minutes.
Find your room's numbers
Add Serial.begin(115200); to setup and Serial.println(adcVal); to the loop, re-upload, and open Serial Monitor. Note the values at your room's darkest and brightest, then write those into LIGHT_MIN and LIGHT_MAX.
Flip the lamp's direction
Swap the last two arguments of map so 0 and 4095 trade places, then re-upload. Whatever your lamp did before, it now does in reverse — set it so darkness makes it glow, and you have a true night lamp.
Logbook
08 Learn it with a hand on the tiller
Coach me through it
Every lesson ships with a code and a machine-readable packet, so an agent can guide you with full context.
Lesson code
TSK-DAY17-NIGHTLAMP
Context packet
How the agent should behave: guide one physical connection at a time, wait for you to confirm, explain terms on request, and always check wiring, board, port, and USB before changing code.