ESP8266 Community Forum

- Thu Apr 16, 2020 9:26 am #86577 Hi, I'm a very new ESP8266 NodeMcu user. I already made some small projects (measuring solar cell output voltage and BMP280 sensor with MQTT link to RaspberryPi). So far so good, as long as I upload my code via USB and the Arduino IDE. I thought that when disconnecting the USB and hook up an external power supply (3.3V) it would work on its own...but nothing happens (and even already blew up one module ). I read a lot about boot modes and pulling up/down some GPIO pins but no luck this far. Some say to pull GPIOO (D3) up to 3.3V...but this pin is currently used for SPI connection towards the BMP280 sensor.

Any suggestions? Thanks in advance.

- Thu Apr 16, 2020 11:26 am #86579 in you have a NodeMcu, it has all the boot configuration pins handled.
power it with a phone charger over the USB connector.

- Thu Apr 16, 2020 12:37 pm #86583 You probably need to give some more information as I have been running NodeMcu boards for years without a problem.

Either use a regulated 5V supply into Vin or through the USB or back feed a regulated feed into 3V3.

If you are running off a Lipo directly it can put out 4.7V when fully charged.

- Thu Apr 16, 2020 2:00 pm #86584 Well, I already tried several options:
- 9V battery to a 3.3V voltage regulator
- lab power supply set to 3.3V
- power adaptor to a 3.3V voltage regulator

None of these worked. Strange thing is that the 3.3V (Voltage output pin) on the ESP only provides about 1.8V (to power sensors etc...). Already replaced the node module...same result.