Power Issue

Hey, I am suffering from a very basic problem to which I don't know the solution. I have an Arduino Mega, a bunch of 5v sensors, and a single channel 5v relay.
The Sensors need more current to operate and so I am using an external 5v 1amp regulated power supply. that's why I have to make GND common supply and Arduino. I am also powering the relay with that power supply and so I have to common the power supply's positive and 5v of Arduino and that's why I may a complete connection of power supply and Arduino via 5v and GND. This power the Arduino also,

The project is working but I think that I should power the Arduino via in(if I want) and that too with at least 7v.

Will, what I am doing cause any difficulty/problem in the project/future? If yes, what should i do? If no, why?

You can power the Arduino with 5V to the 5V pin. There is no need to use the Vin pin.

PerryBebbington:
You can power the Arduino with 5V to the 5V pin. There is no need to use the Vin pin.

but still, it needs 7v at least, right? if yes, what should I do?

No, it doesn't need 7V. It needs 5V, which you can feed in to the 5V pin. If for some reason you want to power it from more than 5V then you can use 7 to 12V on Vin, but there is no requirement to do so. 5V on the 5V pin is enough.

PerryBebbington:
No, it doesn't need 7V. It needs 5V, which you can feed in to the 5V pin. If for some reason you want to power it from more than 5V then you can use 7 to 12V on Vin, but there is no requirement to do so. 5V on the 5V pin is enough.

Ok, Thanks.

It really is better to power the Arduino with the external 5V supply connected to the 5V pin. Connecting a higher voltage to Vin (or the power jack) means that the 5V power is supplied by the onboard 5V regulator. That regulator is not heat sinked so can only supply limited current before it overheats and shuts down. Supplying by external 5V regulator bypasses the weak on board regulator.

7 V - 12 V >> V In pin and barrel >> regulator >> regulated 5 V >> 5V pin, and the Arduino

The recommended max power from the onboard regulator on a Uno, Mega and the like is 1 Watt (by RuggedCircuits). That means that the 5V regulator can safely supply 500mA max with 7V to Vin, but less than 150mA with 12V to Vin. An Uno or Mega will use around 50mA of that. So you need to know how much current that the 5V line must supply and the input voltage to decide if the power strategy will work reliably. If you feed the Arduino Vin with 12V, do not expect the 5V rail to provide 300mA.

Hi,
Can you post a circuit diagram showing your project wiring including power supply connections?

Thanks.. Tom.. :slight_smile: