Powering my project with 15V

Hi everybody,

I have a working spare laptop power supply, that outputs to 15V (for a max of 4A).
I would like to use this to power my arduino and some components of my circuit.
How can I supply stable 5V to Arduino and 15V to the eletronic of my project? The project is made of a bunch of leds and a couple of 2N2222 that are piloted by Arduino.

How can I supply stable 5V to Arduino and 15V to the eletronic of my project?

For Arduino you need >7V (the standard power input). So you may use ie. 7808 voltage regulator.

Arduino will run on 5 volt supply, but you have to be careful that it is well regulated. When you connect Arduino to a PC to program, you run the board off the 5 volt USB port. You can therefore use the 5 volt port to run the board. Running 5 volts into the power jack will not work because the onboard voltage regulator consumes some of the voltage to operate and you will end up running at around 3.7 volts. So use a 7805 regulator to power the board and the 15 volts for the rest. Why 15 volts? Are you doing something with op-amps?

To elaborate on what Pito said, the on-board regulator on the Uno (and probably other versions) accepts from 6-20v, but the developers recommend 7-12v. So, if you have the right barrel jack on your laptop power supply, you could plug it right into the Arduino’s barrel jack. It’s beyond the recommended range, but well within the acceptable range. A fully charged 12v battery is also often beyond 12v, so I think it should be fine depending on how much current you’re running through the Arduino.

To power the 15v circuit, just cut the power cord on the DC side of your supply, and branch the positive and negative wires over to your 15v circuit, and then connect the base pins on the 2n2222s to the digital pins on the Arduino.

In this scenario, you do not need an additional voltage regulator.

Some additional thoughts:
1)After running the board for a couple minutes, check to see if the regulator gets hot, if it does, the regulator Pito recommended (or similar) will be necessary to reduce the 15v to 7-12v.
2)If you don’t have a barrel jack, you can power the Arduino directly through the Vin pin and Gnd.
3)If you do have a barrel jack, you could theoretically run your 15v circuit out of the Vin pin. See this description of the Vin from Arduino’s website:

VIN. The input voltage to the Arduino board when it’s using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

However, there may be a small voltage drop out of the Vin pin (test with a meter if you have one) because of a protection diode, and you should pull 1 amp or less (hopefully a lot less) from the Vin pin because the diode is only rated at 1amp. So if you want the 4amps from your power supply, this second scenario isn’t going to work.

Thanks everybody for the tips. Right now I'm still coding my Arduino, so I use the USB plug to power my Uno, and the laptop power supply to power the board. It is 15V straight from the power supply, so this is why I'm using 15V. When my project is ready I want to bring Arduino far from the computer, so I was thnking about the 15V also for Arduino. I will try both solutions, thanks!

You're welcome and good luck! If my post was helpful, please click the green + on the left (karma)!