Spark Academy — Learn Electrical Engineering by Building

The mission

Build a lamp that switches itself on at dusk, off at dawn, with a knob to set your idea of “dark” — and, because software makes it a two-line change, a fade mode where brightness grows with darkness. This is the complete embedded-systems loop: sense → decide → act, and every stage is a lesson you own: divider sensing (2.2), ADC (11.2), hysteresis (6.1), PWM dimming (Unit 8).

Shopping list (beyond your kit)

Part	Spec	Qty	≈ Cost
Raspberry Pi Pico	Pico or Pico W, with header pins (or solder them — a rite of passage)	1	$5–7
Micro-USB cable	data-capable, not charge-only!	1	$2
Photoresistor (LDR)	GL5528 or similar	1	$0.50
Resistor	10 kΩ — brown·black·orange	1	$0.10
Reused: breadboard, LED, 470 Ω, jumpers, and the 100 kΩ potentiometer from Unit 8. The 9 V battery retires — the Pico runs from USB and its pins speak 3.3 V.

New voltage, new rule

The Pico is a 3.3 V citizen. Power your breadboard rails from its 3V3(OUT) pin — never connect the old 9 V battery to any Pico pin, and never feed a GPIO more than 3.3 V. (Your LED at 3.3 V through the same 470 Ω still lights fine: (3.3 − 1.8)/470 ≈ 3 mA — dimmer than before, and PWM at 100% is its new maximum.)

The wiring

Seat the Pico across the breadboard’s centre gap (USB connector at one end, like the 555’s notch rule at a bigger scale). Pin numbers below are the physical pins counted counter-clockwise from the USB end — the same DIP convention you learned on the 555, forty pins instead of eight:

#	From	To	With
1	Pico 3V3(OUT) — physical pin 36	+ rail	jumper (red)
2	Pico GND — physical pin 38	− rail	jumper (black)
3	+ rail	a free column (the sensor node)	LDR
4	sensor node	− rail	10 kΩ (divider's bottom leg)
5	sensor node	GP26 / ADC0 — physical pin 31	jumper
6	pot outer legs	+ rail and − rail	the pot IS a divider (2.2)
7	pot wiper (middle leg)	GP27 / ADC1 — physical pin 32	jumper
8	GP15 — physical pin 20	LED anode via 470 Ω, cathode to − rail	your standard LED branch
9	Pico USB	computer	the data cable

Notice what the divider does here: bright room → LDR small → sensor node pulled toward 3.3 V → high ADC reading. Dark room → low reading. The code’s comparisons follow from that one sentence.

Breathing life into it

Download the MicroPython firmware file (a .uf2) for the Pico from micropython.org.
Hold the Pico’s BOOTSEL button while plugging in the USB — it appears as a tiny flash drive.
Drag the .uf2 onto it. The drive vanishes; the Pico reboots as a Python machine.
Install Thonny (free, thonny.org), choose MicroPython (Raspberry Pi Pico) as the interpreter — bottom-right corner.
Paste the program below and press Run. Cover the LDR with your hand.
When it behaves, save it to the Pico as main.py — from then on it runs on power-up, no computer needed. Congratulations: you have shipped firmware.

The firmware

from machine import Pin, ADC, PWM
from time import sleep_ms

ldr = ADC(26)            # light sensor divider  -> GP26
knob = ADC(27)           # threshold potentiometer -> GP27
led = PWM(Pin(15))       # night-light LED       -> GP15
led.freq(1000)           # 1 kHz: your Unit 8 dimmer, in code

HYST = 3000              # Lesson 6.1: no chatter at dusk

lamp_on = False
while True:
    light = ldr.read_u16()        # 0 (dark) .. 65535 (bright)
    threshold = knob.read_u16()   # set by the knob

    if light < threshold - HYST:  # definitely dark
        lamp_on = True
    if light > threshold + HYST:  # definitely bright
        lamp_on = False

    if lamp_on:
        darkness = max(0.0, min(1.0, (threshold - light) / 20000))
        led.duty_u16(int(20000 + 45535 * darkness))
    else:
        led.duty_u16(0)

    sleep_ms(50)                  # 20 decisions per second

Two dozen lines, and every one traceable to a lesson: the two ADC reads (11.2), the hysteresis pair of ifs (6.1), the PWM duty computation (Unit 8), the superloop with its polite sleep_ms(50) (11.1).

If it misbehaves

Symptom	Likely cause	Fix
No board in Thonny	Charge-only USB cable, or interpreter not selected	Use a data cable; pick the Pico interpreter bottom-right
LED never lights	LED direction or wrong pin	Long leg toward the 470 Ω on GP15 (physical pin 20)
Lamp logic inverted	LDR and 10 kΩ swapped in the divider	LDR to +, fixed resistor to − (or swap the comparisons)
Knob does nothing	Outer leg wired instead of the wiper	Middle leg to GP27 — same mistake, same fix as Unit 8
Flickers at dusk	HYST too small for your room	Raise HYST — you have a lab above to pick a value

Experiments — now it's software

Breathe: replace the fade math with a slow sine of duty — a MacBook-style breathing lamp. Three lines.
Log the dawn: print(light) each loop and watch sunrise as a column of numbers in Thonny. Your first data logger.
Average 16 ADC reads (11.2's tip) and watch the dusk transition steady itself.
Pico W owners: the same chip has Wi-Fi — a web-controlled lamp is a weekend, not a career.

Where you stand now

Three builds sit on your desk: a blinker you sized with RC math, a dimmer you steered with diodes, and a lamp that senses and decides because you told it how. You can read schematics, size components, debug with Kirchhoff and a multimeter, reason about signals in time and frequency, follow logic from gate to program counter — and now flash firmware. One summit remains: the master course — sampling and Fourier, PID control, the art of real-world tolerances and debugging — ending with the finest full-circle build this course could offer: your own oscilloscope, pointed back at everything you have made.

Program the Night-Light