Question: I'm working on a project where my arduino talks to another device that uses serial communication. I've connected my USB cable to a USB-to-serial adapter, so it can communicate with the device.

The problem I'm running into is powering the device: if I'm using the USB for serial, I can't use it for power. I have made sure that the device isn't turning on by putting 

```
pinMode(13, OUTPUT);
for (int i = 0; i < 10; i ++) {
    digitalWrite(13, HIGH);
    delay(1000);
    digitalWrite(13, LOW);
    delay(1000);
}

```

at the start of the `setup` function: if it works, it should start by blinking LED 13. 

I tried powering it with a 5V power supply through the power jack, next to the USB connector, but that didn't work. Is there something I'm missing? Do I need a different type of power supply?

Answer: 
It seems that my mistake was that I just created new files with another program and simply put them in the project directory. This probably confused the IDE as the files were not included in the build of the project.

Managed to fix this issue by creating new files within the project itself and simply copying my code into them. For VMicro/Visual Studio:

> 
> VMicro\Add Code\Add Empty Arduino .h and .cpp files
> 
> 
>
The question is a bit unclear, however as far as I know, for the included libraries use: 

```
#include <SPI.h> 

```

So the `<` and `>` are used for common libraries which are in the C:\Program files...\Arduino folder 

And for specific (own made or sketch-depending) include files 

```
#include "MyFile.h"

```

should be used, which should be located in the same folder as the sketch file.