Voltage Regulator
Using AMS1117 33 Voltage Regulator with Arduino Uno
What is the AMS1117 33?
A simple fixed 3.3V linear regulator found on countless breakout boards to safely power 3.3V logic from a 5V source. The AMS1117-3.3 takes an input voltage a bit above 3.3V and drops it down to a clean, stable 3.3V output using simple linear regulation — no switching, no configuration, just a dropout voltage and some wasted heat — making it the near-ubiquitous small regulator seen on the back of ESP8266, ESP32, and countless sensor breakout boards whenever 3.3V logic needs to be derived from a 5V supply.
Specifications
| Regulator type | AMS1117-3.3 fixed 3.3V low-dropout (LDO) linear voltage regulator |
| Input voltage | 4.75V–15V DC (practical range; must exceed 3.3V output by the dropout voltage) |
| Output voltage | Fixed 3.3V DC (non-adjustable — the '-3.3' in the part number denotes this fixed version) |
| Dropout voltage | ~1.1-1.3V typical at full rated current |
| Output current | Up to ~1A (with adequate heatsinking/cooling; less at higher input-output voltage differential due to heat dissipation) |
| Package | Commonly SOT-223 surface-mount package on breakout boards, sometimes TO-220 for higher-current bare regulator boards |
| Efficiency | Lower than a switching (buck) regulator — wastes power as heat proportional to the input/output voltage difference and current drawn |
AMS1117 33 Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VIN | Regulator input, 4.75-15V DC |
| 2 | GND | Ground (also the regulator's tab/heatsink connection on some packages) |
| 3 | VOUT | Regulated 3.3V DC output |
Being a linear regulator, the AMS1117-3.3 dissipates the input-to-output voltage difference as heat proportional to the current drawn — fine for small logic loads (tens to a few hundred mA) but it will run noticeably warm and waste real power if pushed near its 1A rating from a much-higher-than-3.3V input; for higher-current or higher-efficiency 3.3V generation, a switching buck regulator is a better choice.
Setting Up AMS1117 33 with Arduino Uno
Wiring
| Component pin | Arduino Uno pin | Note |
|---|---|---|
| VIN | 5V pin on the Uno | Uno's 5V rail is a safe, regulated source for the AMS1117's input |
| GND | GND | — |
| VOUT | Feeds a separate 3.3V-only module (not back into the Uno) | The Uno already has its own onboard 3.3V pin — this setup is for powering an external 3.3V peripheral that needs more current than the Uno's onboard regulator can spare |
No code applies — this is a passive linear regulator. Typical use with an Uno: the onboard 3.3V pin is current-limited (~50mA), so if a 3.3V module needs more than that, tap 5V into an AMS1117-3.3 breakout instead and feed its output to the module. Add a 10µF (or per-datasheet) output capacitor if your breakout doesn't already include one, or the regulator can be unstable.
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