I've successfully migrated and ATMEL328P-UP microcontroller from the Arduino Uno Board to a breaboard, following these instructions: https://www.arduino.cc/en/Tutorial/ArduinoToBreadboard. Everything is OK, the bootloader worked and code is already uploaded an running.
The ATMEL is connected to a pair of sensors, and all the system works using 3.3V. And here comes the problem: I'm using a 5V USB power bank to power up everything. When I make this connection:
USB Power Bank @ 5V -> Arduino Uno board (without the microcontroller) -> 3.3 V Output from the board -> ATMEL/Sensors on the breadboard
everything works just fine! Now I decided to replace the Arduino uno board with an LM317 voltage regulator which gives me the 3.3V needed. The connection is this:
USB Power Bank @ 5V -> LM317 with 3.3 V output -> ATMEL/Sensors on the breadboard
and nothing happens! Is as if there wasn't enough current to feed the ATMEL nor the sensors. I've checked the Vcc/GND pins of the sensors and the ATMEL and they're all getting the required 3.3 V, but for some reason the system seems to be OFF.
What could be happening? I'm sure the USB power bank is at full charge, so it should be able to supply enough current. Any suggestions?