I have an ESP8266-01 WiFi Module and I have some troubles in supplying power to it. I use an Arduino Nano powered by a 9V battery (actually 6x 1,5V AA) through the Vin pin and the GND pin. I power the ESP8266's pin Vcc with Arduino's pin 3v3 and GND is obviously connected to GND. Up to here everything's fine. The ESP8266 turns on. Then I connect ESP's pin CH_PD to 3v3 to enable the chip. This last connection makes the ESP turn off. If I measure the voltage between pin 3v3 and GND while the CH_PD is connected, I find 1.2V. If I measure it without connecting CH_PD, it is 3.3V as expected. Does someone know why?

note 1: If I use an Arduino Uno powered by my laptop through USB, with the same configuration, everything works fine. CH_PD causes no problems at all.

note 2: Arduino Uno is original, whereas Nano is not.

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    \$\begingroup\$ The ESP8266 requires quite a bit of current, peaking at over 200mA. Add to that the draw of the arduino itself and you might be seeing brownouts. \$\endgroup\$ – Hearth Oct 28 '18 at 21:45
  • \$\begingroup\$ I agree with above comment, to solve the problem, consider using a (switched mode) regulator like for example: ebay.com/itm/… to supply power to the ESP module. Being a switched converter, this will also use the battery more efficiently. \$\endgroup\$ – Bimpelrekkie Oct 28 '18 at 21:56
  • \$\begingroup\$ A short [and a little snarky] answer to the titular question would be: "Because Arduino is a microcontroller board, not a general purpose power converter." \$\endgroup\$ – Nick Alexeev Oct 29 '18 at 23:17

The 3.3V from arduino nano (genuine) is supplied by internal LDO in the FT232R chip which can supply up to 50mA. Arduino UNO has a dedicated LDO for 3.3V supply. If you're using a cloned version you'll need to check what is supplying the 3.3V and check the maximum current they can provide. Most likely the chip supplying 3.3V cannot provide sufficient current for your ESP to boot.

  • \$\begingroup\$ Ok, I understand Arduino Nano can't do the job. Thanks for your answer and for the previous comments. So, I suppose a voltage regulator will work... I have a LD33V and it can stand up to 1.5A \$\endgroup\$ – Massimiliano Taverna Oct 30 '18 at 8:14

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