Brownout detector was triggered
Espressif ESP32
Severity: ModerateWhat Does This Error Mean?
Brownout detector was triggered means the ESP32's supply voltage dropped below the safe operating threshold. This is a power supply problem — the ESP32 needs a stable 3.3V (or 5V via USB/VIN). Use a better power supply or reduce power consumption.
Affected Models
- ESP32-DevKitC
- ESP32-WROOM-32
- ESP32-S3
- ESP32-C3
- ESP32-CAM
- Wemos D1 Mini ESP32
Common Causes
- USB port cannot supply enough current (especially during Wi-Fi transmission)
- Long or thin USB cable causing voltage drop
- Wi-Fi transmission spikes drawing up to 500mA
- Too many peripherals drawing power from the 3.3V pin
- Powering the board from a weak battery
How to Fix It
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Use a powered USB hub or a wall adapter instead of a laptop USB port.
The ESP32 can draw up to 500mA during Wi-Fi bursts. Laptop USB ports may not supply this consistently, especially if other devices are connected.
-
Use a short, thick USB cable.
Long or thin cables lose voltage under load. Keep the cable under 1 meter and use a quality cable.
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Add a large capacitor (100-1000uF) across the power pins.
A capacitor smooths out the voltage dips during Wi-Fi transmission spikes. Solder a 100uF or larger capacitor between 3.3V and GND near the ESP32.
-
Reduce Wi-Fi transmit power in your code.
Add WiFi.setTxPower(WIFI_POWER_8_5dBm) to reduce the transmit power. This reduces range but also reduces peak current draw.
Frequently Asked Questions
What is a brownout?
A brownout is a temporary drop in voltage — not a full power loss, but a dip below the minimum the chip needs. The ESP32's brownout detector monitors the voltage and resets the chip if it drops too low, to prevent unpredictable behaviour.
Why does Wi-Fi cause brownouts?
Wi-Fi radio transmission requires bursts of high current (up to 500mA). If the power supply cannot deliver this current instantly, the voltage dips. The ESP32's 2.4GHz radio is the most power-hungry component on the chip.