How to power external LED's

Other Hardware Motors, Mechanics, Power and CNC
1

I am looking at a project in which I'll need to more power to drive LEDs than the Uno 5v can supply. I can see getting an external power supply and a barrel jack receptacle to power the LEDs, but do I still need a separate power supply for the Uno itself? Or can I jumper the positive line from the external supply to VIN? Is there a standard way to accomplish this?

2

Depends on the power supply. If it is a 5V supply then you can power the Uno through its 5V pin - not Vin which needs a minimum of 6.5V. You will also need to connect the power supply negative to Uno GND.

Steve

3

Thanks. Is using VIN ok if the supply is at least 6.5v?

4

According to the general specifications for the Arduino Uno R3, power can be supplied from any of the following:

  • USB
  • 9 V DC jack
  • Vin pin (7-12 V)

It is my understanding that the jack and Vin pins are tied together, so 7-12 V supplied to either should work.

5

Thanks.

Where do I find this specification?

6

Look at the Power section under the FAQ tab for the Arduino Uno Rev3 within the Arduino Store.

7

woolsey:
It is my understanding that the jack and Vin pins are tied together, so 7-12 V supplied to either should work.

Not quite, they are linked by a diode, so that >6.75V will work for Vin but the jack needs more like 7.5V. The diode
prevents damage if the wrong polarity power plug is inserted. The schematic for Arduinos are open-source.