ESP8266 Power issues using 9V battery and LM317 regulator

In my previous post, I made a simple variable power supply intended to power my ESP8266.  I hooked it up and was having some problems.  This is what I found….


For this test, I am going to keep it simple.  I am going to use my FTDI USB to serial cable and see if the ESP8266 reboots when I pull the RESET pin high or low (since I can’t find documentation on which polarity the RESET is).  Here is a simple diagram of the setup.


(Click on diagram to enlarge)


Never got to the toggling test.  The ESP8266 would never even boot up.


  • Probing the LM317 output was showing only about 1.01V being output.  I checked the data sheet and it should be able to output 1.6A.
  • Maybe a big spike during boot up?… So I added a 2200uF cap on the LM317 output.  That still did not help.
  • Probed the 9V battery and it was down to only 2.6V.
  • I took out the 9V battery and used the 5V supply from my Arduino board.  The LM317 output was regulated to 3.3V as expected.  When I used this setup, the ESP8266 booted with no issue.
  • ====> The 9V battery is too weak!!!!  I did buy the battery at the 99 cent store.  Wonder if all 9V batteries are like this so need to go buy a name brand battery to try.


I replaced the 99c store 9V battery (Eveready) with another brand from the 99c store (Sony).  Everything is working great!  I am surprised how big a variance there is with batteries.  I guess you get what you pay for.


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