ESP8266 Community Forum

i am using a USB adapter connected to my computer as power input for the ESP8266 (using its 3.3v output and to it's ground). using arduino serial console i am able to communicate with it well - send and receive data.
when i change the power source from the USB to a tuned regulator that gets 12v input and gives 3.3v output, i cannot communicate with the module - i get strange characters instead for every command that i send.
what is the reason for that? the power input in both cases for the ESP is exactly 3.3v - i verified it with a multimeter.

the usb adapter:
http://www.ebay.com/itm/USB-2-0-to-TTL- ... 258d29444b

the regulator:
http://www.ebay.ca/itm/LM317-Linear-Ful ... 3f3d11c036

the power source dc adapter for the regulator:
http://www.ebay.ca/itm/Portable-DC-12V- ... 2a3f1fc80f

That is a bit strange and I don't see anything wrong with what you describe. When you are using the 12V/3.3V power setup do you still connect the ground of the USB adapter? I'm thinking maybe you forgot and that could be your problem.

Another test might be to take the 5V from the USB adapter and feed that into the regulator. This eliminates the 12V power adapter. Sometimes these power adapter designs are not very good and they don't perform well under light loads. The multimeter might read 3.3V but it is not fast enough to catch dips in the Vcc level. These dips are not fast enough for the multimeter to see but they are long enough to cause troubles with the ESP.

Also, it is not a good idea to use 12V to 3.3V, that is a lot of wasted energy. If you have an old phone charger you can use the 5V output of that to feed your regulator and that would be better.

Like GeorgeIoak already mentioned: check if ESP & usb serial adapter have a common ground.
Also the LM317 is a poor choice in your application. With 12V input, the LM317 needs to dissipate up to 2W in heat. If not properly heatsinked, its thermal protection might kick in and shutdown (possibly causing a reboot-loop for the ESP).
If you cannot reduce the input voltage (eg. if other parts of your circuit require 12V), you should use a buck instead of a linear regulator, such as:
http://www.ebay.ca/itm/mini-DC-DC-Conve ... 0788623921

I made a few tests thanks to your reply - I didn't know that there are unstable power sources which I cannot see their instability with my multimeter and i suspect that was the reason for my problems.
I am using a 5v power adapter with the regulator to 3.3v -> ESP power and so far it works perfectly. I will make further tests with other power sources - this module seems to be VERY sensitive to its power source.

BTW - i am using common ground of course.

Thanks a lot