How to power Arduino with VIN?
Here’s the short, safe guide to powering an Arduino via VIN.
1) What VIN is (and isn’t)
VIN feeds the board’s 5 V linear regulator. Use it when your source is \> 6 V and < ~20 V.
Recommended: 7–12 V (sweet spot: 7–9 V to reduce heat).
Do NOT put 5 V on VIN. If you already have a regulated 5 V source, feed the 5V pin instead.
On most boards, the barrel jack and VIN go to the same regulator path, but the barrel jack has reverse-polarity protection (a diode). VIN usually bypasses that, so be careful with polarity.
2) Basic wiring (VIN as input)
(+) Supply 7–12 V -> VIN
(–) Supply GND -> GND
That’s it. The regulator makes 5 V for the board.
3) Current & heat (most common pitfall)
The onboard regulator burns off the extra voltage as heat:
Power dissipated ≈ (VIN − 5 V) × I_load
Example: 12 V in, drawing 200 mA (board + sensors) → (12−5)*0.2 = 1.4 W → HOT.
Tips
Prefer 7–9 V if you’ll draw >100 mA from 5 V.
For heavier loads, use a buck converter to 7–9 V (into VIN) or directly to 5 V (into 5V pin).
4) Board notes
Arduino Uno/Mega/Leonardo/Nano (VIN or RAW): 7–12 V recommended.
Due: also OK on VIN, but it’s a 3.3 V logic board—don’t feed 5 V into I/O.
Nano (older “RAW” pin) = VIN.
Clones can differ—if in doubt, check the schematic.
5) Using VIN as an output?
If you power the board from the barrel jack or VIN, the VIN pin will sit near your input voltage. It’s not regulated—don’t power other stuff from it unless you know what you’re doing.
To power external modules at 5 V, use the 5V pin, but remember the regulator’s heat limits (see §3).
6) USB + VIN together?
- Official boards have auto power selection, so using USB while VIN is present is typically fine. Some clones aren’t as robust—avoid weird power loops (don’t back-feed the PC via 5V).
7) Batteries that work well
Not great: 9 V “PP3” rectangular battery (can’t supply much current).
Better: 6×AA NiMH (≈7.2 V) → VIN, or 2–3-cell Li-ion/LiPo through a buck to 7–9 V (VIN) or clean 5 V (5V pin).
8) Quick checklist
Correct polarity to VIN/GND (no protection on many boards via VIN).
Stay in 7–12 V range (ideally 7–9 V).
Estimate heat with (VIN−5)×I; if >0.8 W, use a buck converter.
Common ground with your peripherals.
