Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)

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By jcdrb
#90210 My ESP-12F is not powering up using an AMS1117 (3.3V) voltage regulator and a 12V 3A power supply. The LED flashes once as the barrel jack is inserted and then nothing.

Here is the schematic:


It powers up fine if I use the 3.3V output from a Node MCU using pin 2 on the 6 pin header on the right of the schematic.

I also measure 3.3V on the VCC pin of the ESP-12F with my multimeter when using the 12V power supply and around 3.1-3.2 when using the Node MCU as power.

Any ideas what the issue could be??

User avatar
By eriksl
#90225 Otherwise:
- check the voltage in real life, if the ESP is drawing more current than the combo of regulator and wiring can supply, the voltage will be lower. There is a current surge when the ESP startups due to RF calibration, be prepared that your power supply must be able to supply 500 mW immediately.
- connect a serial port and simply see what happens, maybe it does work but stops with an error message
- always add ceramic capacitors to electrolytic capacitors. I know most (all?) ESP boards have power decoupling capacitors themselves, I'd still add a 100 nf ceramic capacitor near the chip or board.
- did you follow the instructions on the datasheet of the voltage regulator on power decoupling (mostly found in the "application notes" section.
- if you're going down from 12 V to 3V3, that's a big difference, especially when the ESP is drawing 500 mW. It means 9 Watts of power dissipation. Your regulator may not be up to that (very probably). I always recommend to use a (switching) buck DC/DC converter to do the main conversion, from 12 V to about 4V5. It will do that will minimal loss and most of them at at least 2 A without problems. Then do the final conversion with a lineair regulator (like this one or one that is especially designed for this purpose: LM3914) and then it will have to dissipate almost no power (1V2 @ 500 mW = 0.6 W). The advantage of using a lineair converter in addition to the DC/DC converter is that it will smooth out a lot of the high frequency ripple that DC/DC converters tend to generate. I am using this scheme to even go down from 20 V (laptop power supply) without issues.