DIY hardware list

From the MCU at the heart of it to the sensor that reads the room: the modules, ICs, and boards that show up in every DIY electronics build — with the specs you need to pick one without reading a datasheet.

Quick reference

The ten parts that cover most builds — grab these first, then dig into the full tables below when you need the long tail.

• ESP32 — Wi-Fi + BLE MCU · 3.3 V · 4 MB flash · 30+ GPIO
• Arduino Uno — 5 V beginner board · ATmega328P · shield ecosystem
• Pi Pico (RP2040) — dual Cortex-M0+ · 3.3 V · PIO state machines
• STM32 Blue Pill — Cortex-M3 · 72 MHz · RTOS / PWM-heavy
• DS18B20 — 1-Wire digital temp · ±0.5 °C · waterproof probe
• BME280 — I2C temp + humidity + pressure · 0x76/0x77
• MPU6050 — I2C 6-axis IMU (accel + gyro) · 0x68
• DRV8825 — stepper driver · 1/32 microstep · 2.2 A
• SSD1306 — 128×64 OLED · I2C 0x3C · only 4 wires
• LM2596 + TP4056 — 3 A buck step-down · 1 A Li-ion charger

Microcontrollers & boards

Pick the brain first. The “big four” cover 90% of projects; the table fills in the long tail.

1. ESP32

Wi-Fi + BLE on-chip
3.3 V · dual 240 MHz
4 MB flash · 30+ GPIO

2. Arduino Uno

Beginner standard
5 V · ATmega328P
32 KB flash · 14 GPIO

3. Pi Pico

RP2040 · 133 MHz
3.3 V · dual Cortex-M0+
2 MB flash · 26 GPIO

4. STM32

Performance / RTOS
3.3 V · Cortex-M3/M4
64–1024 KB flash

KEY: 3.3 V vs 5 V is the first decision. ESP32, ESP8266, STM32, RP2040 run at 3.3 V logic; Arduino runs at 5 V. Match your sensors and drivers to the logic level or add a level shifter — see Selection tips.

1. Pick the MCU — ESP32 for wireless, Uno for 5 V shields, Pico for PIO, STM32 for raw speed.
2. Choose the sensors — Match voltage and bus: I2C is the default, 1-Wire for temps, analog for simple reads.
3. Pick the drivers — Any moving or high-current load goes through a driver or MOSFET, never a GPIO.
4. Size the power — Add up stall current, pick a supply with headroom, and common-ground everything.
5. Assemble & test — Wire module by module, test each in isolation, then integrate. Sensor (MPU6050 · I2C) → MCU (ESP32 · brain) → Driver (DRV8825) → Output (NEMA 17)

Sensors

Everything that reads the physical world: temperature, motion, light, gas, current, position.

Analog read (voltage divider)

Resistive sensors (LDR, thermistor, flex) need a fixed resistor to form a divider; the ADC reads the midpoint.

VCC ──[sensor]──┬──→ A0
                 │
                [10k]
                 │
                GND

int raw = analogRead(A0);

1-Wire (DS18B20)

Many sensors share one pin, each with a unique 64-bit address. A 4.7k pull-up to VCC is required.

DQ ──┬──→ pin 2
     [4.7k]
      VCC
# OneWire + DallasTemperature lib

⌁: Prefer digital sensors (DS18B20, DHT22, BH1750) over raw analog ones — they’re calibrated at the factory and immune to ADC noise.

Communication modules

Wireless and wired links: Wi-Fi, Bluetooth, LoRa, RF, RS-485, CAN, Ethernet, GSM.

Range vs power, at a glance

Bluetooth LE   → ~10 m
nRF24L01       → ~100 m
Wi-Fi          → ~100 m
LoRa (SX1278)  → 1–10 km

Pick by distance

Short and battery-friendly: BLE. Medium and point-to-point: nRF24L01. Long and sparse: LoRa. Anything that needs the internet: Wi-Fi or GSM.

# LoRa needs a matched pair
SX1278 on both ends, same
frequency + sync word

I2C

• Data / clock — SDASCL
• Pull-ups — 4.7kVCC
• Wires — VCCGNDSDASCL

SPI

• Clock / data — SCKMOSIMISO
• Per-device select — CS
• Wires — VCCGNDSCKMOSIMISOCS

UART / 1-Wire

• UART — TXRX
• 1-Wire — DQ4.7k
• Cross-wire — TX↔RX

Actuators & drivers

Making things move and switch: motor drivers, servos, relays, MOSFETs, solenoids.

• 50 Hz — servos (SG90, MG996R)
• 490 Hz — Arduino default PWM — pins 3, 9, 10, 11
• 980 Hz — Arduino pins 5, 6
• 25 kHz — LED dimming / motor — above audible whine
• 1–10 kHz — DC motor PWM (L298N / TB6612)
• 38 kHz — IR remote carrier (TSOP38238)

Stepper wiring (DRV8825)

EN ── GND (or a pin)
DIR ── pin 8
STEP ── pin 9
VMOT ── 12 V + 100 µF cap
B2 B1 A2 A1 ── NEMA 17

Servo sweep

Servos take a 50 Hz pulse; 1 ms ≈ 0°, 1.5 ms ≈ 90°, 2 ms ≈ 180°.

servo.attach(9);
servo.write(90);   // center
servo.write(0);    // min
servo.write(180);  // max

!: Never drive a motor from a GPIO pin. A motor’s stall current can be amps; a GPIO sources ~20 mA. Always go through a driver (L298N, TB6612, MOSFET) and a separate power supply with a common ground.

Displays & HMI

Ways to show output and take input: LCDs, OLEDs, TFTs, e-paper, keypads, encoders.

Character LCD

Text-only, cheap, readable in daylight. Uses 6+ pins, or 2 with an I2C backpack.

lcd.init();
lcd.backlight();
lcd.print("Hello");

OLED

Crisp, tiny, no backlight, 4 wires. Great for status readouts and small graphs.

display.clearDisplay();
display.setTextSize(1);
display.println("ESP32");

E-paper

Keeps the image with zero power; refresh takes seconds and ghosting is normal.

display.setRotation(0);
display.display(); // full refresh
display.powerOff();

✓: OLED over LCD: SSD1306 needs only 4 wires (VCC, GND, SDA, SCL) and no contrast pot, so it’s the default choice for quick readouts.

Power & storage

Getting the right voltage, keeping time, and holding data between power cycles.

Linear vs switching

Linear (7805, AMS1117) is quiet but burns the difference as heat. Switching (buck/boost) is efficient but can be noisy for analog readings.

# 12 V → 5 V, 500 mA
# linear wastes: (12-5) × 0.5 = 3.5 W heat
# buck wastes:  ~0.3 W

RTC keeps time

The MCU’s millis clock resets on power loss. A DS3231 on I2C with a coin cell keeps wall-clock time across reboots.

# Wire: VCC→5V  GND→GND
#       SDA→A4   SCL→A5
# read via RTClib, set once

2× 18650 in series = 7.4 V
# boost for 12 V rails, or
# buck down to 5 V / 3.3 V

2× 18650 in parallel = 3.7 V
# double mAh, same voltage
# balance cells first!

Non-typical parts

The odd, the vintage, and the gloriously unnecessary — for when a normal project won’t do.

nixie vacuum haptic fog radiation receipt printer gesture dust

Nixie / VFD basics

Both need a high-voltage rail (170–400 V) from a boost converter plus a driver chip. Multiplex the digits to save pins.

170 V ── anode driver
cathode ── K155ID1 ── GPIO
# never touch HV pins powered

Thermal printer

Speaks ESC/POS over UART. Feed it 5–9 V with a beefy supply — the heating head spikes to ~2 A.

Serial1.begin(9600);
Serial1.write(0x1B); Serial1.write('@'); // init
Serial1.println("Hello, receipt");

!: High voltage lives in this section. Nixie, VFD, and Geiger circuits run at 170–400 V — lethal if you touch the wrong node. Power down, discharge capacitors, and use an isolation transformer when probing.

Selection tips

Six rules that save boards, hours, and money — before you solder anything.

3.3 V vs 5 V logic

ESP32, ESP8266, STM32, and RP2040 GPIOs are not 5 V tolerant. Feed them a 5 V signal and you can kill the pin. Use a level shifter or a resistor divider for 5 V inputs.

5V signal ──[1.7k]──┬──→ 3.3V pin
                    [3.3k]
                     GND

I2C address conflicts

Two devices can’t share a bus address. Watch the usual suspects: 0x27/0x3F LCD backpacks, 0x68 MPU6050/DS3231, 0x76/0x77 BMP280, 0x3C OLED.

// I2C scanner sketch
// prints every address found
Wire.beginTransmission(addr);

Current draw

Size the supply for stall current, not running current. Motors, servos, and relays spike at startup; a weak supply browns out the MCU.

SG90 stall   ≈ 650 mA
MG996R stall ≈ 2.5 A
NEMA17 coil  ≈ 1.2 A

Pin count & shared pins

I2C uses SDA/SCL, SPI uses SCK/MOSI/MISO + one CS per device. On ESP32, some pins are input-only or strapping pins — avoid GPIO 0/2 for arbitrary use.

SPI:  SCK, MOSI, MISO, CS
I2C:  SDA, SCL
UART: TX, RX

Genuine vs clone

Clones often swap the FTDI chip for a CH340 (needs a driver) and may skip protection circuits. They usually work — just verify the board voltage and USB chip before buying in bulk.

# check the USB-serial chip
ls /dev/cu.*    # CH340 → cu.wchusbserial*
                # FTDI  → cu.usbserial*

ESD & reverse polarity

Discharge static before touching bare ICs, and add a flyback diode across any relay, solenoid, or motor. Double-check capacitor polarity and battery orientation — one reversed electrolytic pops.

coil + ──|>|── coil -
   flyback diode across
   every inductive load

Li-ion battery safety

Never discharge a bare 18650 below ~2.8 V or charge above 4.2 V — use protected cells or a DW01A + 8205A board. Don’t mix cells of different age or capacity, and retire any cell that puffs.

4.2 V full · 3.7 V nominal
2.8 V empty · don't go below
TP4056 charges at 1 A

2G / 3G sunset

Carriers are switching off 2G and 3G region by region, so SIM800L-based builds will stop connecting. For new cellular projects use LTE Cat-M / NB-IoT (SIM7000, SIM7080G) or Wi-Fi via an ESP32.

2G  → sunset, avoid new builds
4G  → SIM7000 / SIM7080G
IoT → NB-IoT / LTE Cat-M

5 V → 3.3 V divider R1 1.7kΩ · R2 3.3kΩ ratio 2:3 level shifter bidirectional

• INPUT — High-impedance read. Floats if nothing drives it — use INPUT_PULLUP for buttons.
• OUTPUT — Drive high/low. ~20 mA max per pin — enough for an LED, never a motor.
• PWM — Fast on/off duty cycle: dim LEDs, drive servos, set motor speed.
• ANALOG — analogRead() on ADC pins only; 0–1023 (10-bit) on AVR.

!: Most blown boards come from one mistake: connecting 5 V logic to a 3.3 V input, or a reversed power supply. Check voltage twice, then power up.