Breadboard Arduino not working with external power source

Hi,

I am attempting a project that I would like to eventually work by itself without the need for an Arduino board. I have created the project as a standalone on a breadboard and tested it with power coming from the Arduino's 5v power line. (Nothing else is connected to the Arduino board apart from 5v power). With power coming from the Arduino everything works as expected. I then followed the instructions on the Arduino on a Breadboard page for creating a 5v regulated power supply, and my project did not work correctly: only input from one of the four buttons I was using was recognised. I measured the voltage from my power supply circuit and it read 5.1v, so I presumed that this was not the problem.

My project consists of four pushbuttons as inputs with an 8x8 LED matrix controlled by a MAX7219 IC as an output. I measured the current drawn from the entire project and it was around 0.5A. The input power source going to my 5v regulated power supply is from a 12v, 5A power adaptor.

Does anyone know why I am experiencing problems? Thanks in advance, Andrew

sorry, but this is not very clear, and without seeing anything.....

(Nothing else is connected to the Arduino board apart from 5v power). With power coming from the Arduino everything works as expected.

what do you mean ? you used the arduino board as a .... PSU (!?) ?? and when you replace the power supply with the one you've done, it doesn't work anymore ?

which means that your entire project (standalone "arduino" + inputs/outputs ) works OK if powered from a arduino's 5V pin ? if yes, than your home made power supply is faulty .

could you post a picture of your wiring ? and also a schematic of your project ? without these elements, we can only guess, and I'm afraid no answer will be really useful

There's no reason why it would not work. Recheck all your wiring starting from the power regulator, in particular the GND/VCC wires.

Please, post a picture of your breadboard + a schematic

Hi,

Thanks for the advice. I checked all my connections, and I discovered that my 12v power supply was indeed faulty. Sometimes it worked, sometimes it didn't. After about 5 tests with a multimeter I eventually found it to be outputting nothing.

Sorry for the easy fix, Andrew