| Arduino Nano (clone) | Arduino Pro Mini (clone) | |
|---|---|---|
| Chip | ATmega328P | ATmega328P |
| Versions | 5 V / 16 MHz | 5 V / 16 MHz or 3.3 V / 8 MHz |
| USB | On board — CH340 on most clones | None — needs a USB-serial adapter with a DTR pin |
| Analog inputs | 8 (A6, A7 analog-only) | 8 (A6, A7 analog-only; A4–A7 are inner pads on many clones) |
| Board size | About 18 × 45 mm | About 18 × 33 mm |
| Idle draw (board) | USB chip and power LED always on | Power LED and regulator can be removed for µA-level sleep |
| Typical price in India | ₹250–400 | ₹200–350, plus ₹100–200 once for a USB-serial adapter |
Both boards carry the same ATmega328P as the Uno, so the same sketches and libraries work on all three. The difference is everything around the chip. Board figures are from the official Nano and Pro Mini documentation; prices are indicative for clones.
The Nano: the Uno you can plug into a breadboard
- USB is built in. Plug in, pick Arduino Nano, upload. Most Indian clones need Processor → ATmega328P (Old Bootloader).
- 5 V logic — works directly with 5 V modules, like the Uno.
- Best for: bench projects, robots, anything that stays near a USB cable or a 5 V supply.
Setup details and pinout are on the Arduino Nano hub.
The Pro Mini: the one you leave inside the project
- No USB. You upload through a USB-serial adapter (CH340, CP2102 or FTDI) wired to the 6-pin header. The adapter’s DTR pin must go to the Pro Mini’s DTR/GRN pin, or you’ll have to tap reset by hand at the right moment.
- 3.3 V / 8 MHz version runs straight from a single Li-ion cell (through its regulator, or with care directly) and talks to 3.3 V sensors without level shifting.
- Low power. With the power LED removed (and the regulator, if you feed it a clean voltage), an ATmega328P in power-down sleep draws only microamps. The Nano’s USB chip and LED can’t be switched off, so it never gets close.
- Smaller and cheaper once you own one adapter for all your Pro Minis.
Gotchas
- Pick the right version in the IDE. Tools → Board → Arduino Pro or Pro Mini → Processor: choose the 3.3 V / 8 MHz or 5 V / 16 MHz option to match your board. The wrong one uploads but every delay and baud rate is off by a factor of two.
- Pin positions vary between clones, especially A4–A7. Check your board’s silkscreen before soldering.
- Don’t power a 3.3 V Pro Mini’s VCC pin with 5 V from the adapter — set the adapter’s jumper to 3.3 V.
Verdict
| You want… | Pick |
|---|---|
| A small board for learning and prototyping | Nano |
| A battery sensor that sleeps for months | Pro Mini 3.3 V, LED removed |
| Many copies of a finished project | Pro Mini — one adapter, cheap boards |
| Plug-and-play with no extra hardware | Nano |
Need Wi-Fi as well as low power? Neither has it — see best boards for battery projects.