Catalogue

An adjustable step-down regulator on a small board — feed it a higher DC voltage, turn the trimmer, get a lower one out. This is how you run 5 V logic off a 12 V battery without cooking a linear regulator. Set the output before you connect anything to it: power the input, turn the trimmer while watching a meter on the output, then wire up your load. The trimmer is multi-turn, so it takes several rotations to move — that is normal, not a fault.

Rubber-tyred wheels that push onto the 3 mm D-shaft of an N20 gearmotor. Sold singly, so a two-wheel robot needs two and a four-wheel one needs four. The D-shaped bore only goes on one way round, which is what stops the wheel slipping on the shaft under load.

A micro metal gearmotor with a 3 mm D-shaft — small enough for a palm-sized robot, geared enough to actually move it. 300 rpm is the middle of the N20 range: quick enough for a line follower, slow enough to have usable torque. Run it from a driver, not from a microcontroller pin. The N20 wheels we stock fit this shaft directly.

Classic Bluetooth serial. Pair it with a phone and anything you print to the serial port arrives in a terminal app — the quickest way to add a remote control or a data readout to a project without touching Wi-Fi. The HC-06 is slave-only: a phone or PC can connect to it, but it cannot initiate a connection to another device. If you need two modules talking to each other, you want an HC-05 for at least one end. Also note it is Bluetooth Classic, not BLE, so it will not pair with iPhones — Android and Windows only.

A dual H-bridge on a board with a heatsink and screw terminals — two DC motors forwards and backwards with speed control, or one stepper. The workhorse for small robots and anything with wheels. It is an older bipolar design and drops a couple of volts across the bridge, so motors run slightly slower than the supply suggests and the heatsink gets warm under load. The on-board 5 V regulator can power your microcontroller, but only with the jumper fitted and the motor supply under roughly 12 V — above that, remove the jumper and feed the logic separately.

The standard four-pin ultrasonic ranger. You pulse TRIG, time how long ECHO stays high, and convert to distance. Cheap, reliable enough for obstacle avoidance and tank level, and the first sensor most robots get. Worth knowing: it does not see soft or angled surfaces well — cloth absorbs the pulse and a surface tilted away reflects it elsewhere. ECHO idles at 5 V, so on a 3.3 V board (ESP32, Pico) put a divider on that pin.

The official RP2040 board — dual-core, and unusually well documented for the price. Its distinguishing feature is PIO: programmable state machines that generate or capture timing-critical signals in hardware, so driving LED strips or a bit-banged protocol does not cost you the main CPU. Runs MicroPython or C. Ships with no headers soldered, and 3.3 V GPIO that are not 5 V tolerant. If you need Wi-Fi, you want the Pico W, not this.

An Arm Cortex-M3 board for when an AVR runs out of speed or peripherals. Considerably more capable than an Uno for the money, and the usual step up for motor control, signal work, or anything needing real timers. Two well-known quirks of this board: many clones ship with the wrong USB pull-up resistor fitted, so USB may not enumerate until it is changed, and there is no USB bootloader out of the box — most people program it with an ST-Link V2 through the SWD header. Budget for an ST-Link if you do not have one.

The ESP32's older, cheaper sibling: single core, Wi-Fi only, and still perfectly good for anything that just needs to get a reading onto a network. If your project is a sensor that posts to a server every minute, this does it for less. 3.3 V logic, not 5 V tolerant. Note the silkscreen labels (D1, D2...) do not match the GPIO numbers you use in code — D1 is GPIO5, D2 is GPIO4. Keep a pinout to hand.

An ESP32 with a camera module and a microSD slot, sold as one board. It runs a web server that streams video over Wi-Fi with about ten lines of setup, which makes it the cheapest way to put a camera on a network. The gotcha that catches everyone: there is no USB port on it. You need a separate USB-to-TTL adapter to program it, and you must jumper GPIO0 to GND to enter flash mode, then remove the jumper and reset to run. Order an adapter with it if you do not already have one.

Dual-core ESP32-WROOM-32 with Wi-Fi and Bluetooth on board. This is the part that replaces an Uno plus a wifi shield plus a bluetooth module, usually for less than any one of them, which is why most new connected projects here start on it. GPIO are 3.3 V and not 5 V tolerant — a 5 V sensor output needs a divider or a level shifter before it touches a pin. Boards come as 30-pin or 38-pin; ask if your enclosure or shield depends on which.

The same ATmega328P as the Uno in a package that drops into a breadboard, which is what you want once a project stops being an experiment and starts being a thing that has to live in a box. Two things worth knowing before you order: A6 and A7 are analog-input only and cannot be used as digital pins, and the USB connector varies by batch — mini-B, micro or USB-C. Ask before ordering if the connector matters to you.

The board most people start on, and the one most Kenyan workshops keep a drawer of. An ATmega328P at 16 MHz, 14 digital I/O and 6 analog inputs, powered over USB-B or a barrel jack. Shields stack straight onto it, which is why it stays in service long after you have outgrown it. Stock here is Arduino-compatible rather than Italian-made, so the USB-serial chip is usually a CH340 — on Windows you may need the CH340 driver before the port shows up. If uploads fail with an avrdude sync error, try Tools > Processor > ATmega328P (Old Bootloader).

A small single-core S2 board with native USB, which is the interesting part: it can present itself to a computer as a keyboard, a mouse or a mass-storage device without any extra hardware. Good where board space is tight. Note the S2 has Wi-Fi but no Bluetooth — if you need BLE, take the plain ESP32 or an S3 instead. Also 3.3 V logic, not 5 V tolerant.