ESP8266 Community Forum

- Wed May 03, 2017 12:04 pm #65514 So, this is probably a dumb question, but in reading various Google results, I can't quite find a simple answer.

The use of 3.3 volts vs 5 volts to power the ESP8266?

I'm trying to design a device using a photosensor to detect the presence of light.
The project I'm going to modify is here:
https://www.childs.be/blog/post/how-to- ... sp8266-12e
In the fritzing diagram, it appears to use the 3.3v pin, a GND pin, and the ADC pin.

My stoopid question is = do I have to provide a 3.3 volt power source on that "red" rail of the breadboard, so that both the ESP8266 _and_ the LDR/photoresistor are powered at 3.3volts via that red rail?

Or is that 3.3v pin on the ESP8266 actually _providing_ the 3.3 volt source for the LDR, and the author of the article has simply omitted the fact that they are powering the ESP8266 over the 5v USB port?

I may be asking for a bit of other help - I'll be trying to have a voltage (light) threshold trigger the sending of some sort of alert via email/SNMP trap, or other network-oriented method, so once I get the LDR part working, and set up the physical light detection conditions, I'll be ready to move on to 'what to do when light is detected' phase...

Thanks in advance! Tim

- Mon May 08, 2017 1:32 pm #65717 Don't put 5v on your ESP; you'll fry it.

- Mon May 08, 2017 1:37 pm #65718 The board gets 5 volts from the USB cable. There is a 3.3 volt regulator on the board that supplies the ESP8266. That 3.3 volt supply is what is connected to the LDR.

- Tue May 09, 2017 3:00 pm #65776 Yea. The board is providing 3.3V for the LDR from its on-board regulator. The actual power comes in on the USB cable. (Although you can power the board externally by providing 3.3V on the same pin (or 5V on the Vin pin?)).

The author perhaps assumed that the readers would be powering and programming the board by the USB cable anyway.