Voltage Regulator
Using AMS1117 33 Voltage Regulator with Arduino Uno
What is the AMS1117 33?
AMS1117 33 practical reference
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.
Key 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
Pinout and connection notes
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.
- VIN: Regulator input, 4.75-15V DC
- GND: Ground (also the regulator's tab/heatsink connection on some packages)
- VOUT: Regulated 3.3V DC output
Integration checklist
- Confirm the exact part number and breakout-board revision.
- Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
- Check controller pin assignments and bus address or interface mode against the example code.
- Power up with external loads disconnected, then test signals before full integration.
- If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.
Troubleshooting and reproducibility
Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.
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 |
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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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