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Brownout detector was triggered

One of my sensor pods (ESP32 D1 Mini) browns out every time it starts. I think it’s been going on the whole time.

But now it’s stuck. It won’t start the program, just keeps starting and browning out.

How can I prevent triggering the brownout detector?

If it is definitely a brownout, then you are running with insufficient power. You might need batteries with more capacity, or a power supply rather than a phone charger. Etc. Check the data sheet for actual power requirements.

If this was an Arduino Uno then there’s another cause. The fuse settings are incorrect for a 16 MHz ATmega328. The brownout detection us fused at too low a voltage for that speed. It will reset long before browning out.


This morning, it appears to be working. BME 680 sensor is frequently not found, and that’s where I am. So it’s passing the brownout detector failure.

Do you know the capacity of the power supply? Output volts times amps = watts. 5V and 2A will be 10W for example.

It’s possible that your sensor dropping off is also power related, perhaps you have too much “stuff” (I know all the technical terms!) hanging off of one too small, power source.

If you have a multi-meter, stick it into circuit between battery + and board, and measure current. I suspect you will be drawing too much, causing the brown outs. Either this, or you have a dodgy sensor somewhere that may be shorting some power to ground.

All guesswork of course, but potentially helpful.


Thanks Norm,
I’ll get around to measuring, but the brownout pod 3 is a D1 Mini with BME680 and VEML for Uv, with one 5V smoke sensor, MQ-2.

The R32 has four 5V sensors with a 3V BME 680, and that runs like a champ. It’s the only one running right now, because I failed to build a shield for Pod1 and Pod3 is refusing to detect the BME680, so it isn’t browning now.

Hi Joe,

I’ve done a rough calculation based on the data sheets for those sensors and the D1 Mini. Your total load is somewhere in the vicinity of 264mA at 5V which is 1.32 watts.

The biggest drain is the heater for the MQ-2 which draws 0.18 A (180 mA) at 5V for the heater coil. I’d say that your power source needs to be 1500 mA at 5V minimum. Some devices draw a lot of current at startup.

The D1 Mini has WiDFi and BLE doesn’t it? BLE apparently, can cause brown outs. Are you using BLE?


I don’t like BLE. Too much infrastructure.

So I’m not using JSON at all in this program. I’m deleting the library.

Try to connect 1000uF cap at 3V3 rail.

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