Can I connect Vin and 5V when powering 5V on Vin?

I'm trying to find a quick fix for solving the 4.5V on the 5V pin of the yun.
So I wonder... can I simply connect the Vin and the 5V when the yun is powered with 5V on Vin?
Best regards
Jantje

bump.

can I simply connect the Vin and the 5V when the yun is powered with 5V on Vin?

No.

Connect an external 5V to the 5V pin only or connect Vin to 6.5V or above only.

Grumpy_Mike:

can I simply connect the Vin and the 5V when the yun is powered with 5V on Vin?

No.

Connect an external 5V to the 5V pin only or connect Vin to 6.5V or above only.

Warning:
This is plain wrong for the Yun, you will damage it. Vin must be 5V.

And to the OP, I see nothing wrong with connecting Vin and 5V together on the shield, as there is a diode on the 5V output which will be reverse biased (and blocking) if the 5V pin is connected to a voltage higher than is produced by the Yun. I am actually planning on doing it myself as my proto shield has the 5v regulator supplying Vin.

This only applies to the Yun, do not do it on other Arduinos.

Grumpy
Did you notice this is about a yun which has different power specifications than al other Arduino's?
http://arduino.cc/en/Main/ArduinoBoardYun states

VIN. The input voltage to the Arduino board. Unlike other Arduino boards, if you are going to provide power to the board through this pin, you must provide a regulated 5V.
5V. The power supply used to power the microcontrollers and other components on the board. This can come either from VIN or be supplied by USB.

This post Arduino Yun 5v pin doesnt give me 5v. - #6 by sonnyyu - Arduino Yún - Arduino Forum shows schematics which make me think it is ok to power Vin and 5V with 5V but I'm not an electronics guy and I'm not sure it is the right shematics :~ so I'd like to be sure.

This posts mentions shorting Vin and 5V Two diode between VIN and +5V: wrong design choice? - Arduino Yún - Arduino Forum
This post states you can probably do so Power question - #3 by system - Arduino Yún - Arduino Forum and someone else states he would never do so :~

I don't want to break my expensive yun so I'd like to be really sure. If you say I can or can't I'm sure enough, but I want to be sure you didn't miss the yun part :smiley:

Best regards
Jantje

I can let you know, when I do it, next time I have it out of the greenhouse.

bjarne:
I can let you know, when I do it, next time I have it out of the greenhouse.

great txs
Jantje

As I understand it, you connect VIN to regulated 5V. You can power other devices from the +5. But if you have a lot to draw power it is better to have an independent source for the other devices you connect.

Grumpy
Did you notice this is about a yun which has different power specifications than al other Arduino’s?

Sorry missed that.

This post http://forum.arduino.cc/index.php?topic=209836.msg1542386#msg1542386 shows schematics which make me think it is ok to power Vin and 5V with 5V but I’m not an electronics guy and I’m not sure it is the right shematics

Well if that schematic is right you can not power the Yun through the 5V pin. There is a diode in that line so that pin is for outputting power only, you will not be able to power it through that pin. I would not attach a source of power to the 5V pin.

The Vin has a series diode as well so supplying 5V to that will result in about 4.5V going to the 5V internal line.

I'll play sure and won't connect them then.
Thanks
Best regards
Jantje

I just connected +5V out of my 5 Volt regulator on the pro to shield to both the Vin and +5V pin of the Yun. As expected that gives my a full +5V to my sensors and everything works fine. The diode in the +5V output becomes reverse biased, so it prevents the 5V from 'entering' through the +5V pin.

It works great !

The diode in the +5V output becomes reverse biased, so it prevents the 5V from 'entering' through the +5V pin.

In which case why do you connect your 5V pin to Vin. If it becomes reverse biased (which it does ) why bother connecting anything to it?

Because it still gives me the option of powering the Yun from the USB port and have the +5V output available for the shield, albeit at the reduced voltage by the diodes. I sometimes use this when I play on my desk.

bjarne:
Because it still gives me the option of powering the Yun from the USB port and have the +5V output available for the shield, albeit at the reduced voltage by the diodes. I sometimes use this when I play on my desk.

Exactly. I have two Yun's running essentially 24x7 since November. Each is powered by an 5V, 2A wall wart feeding into Vin and 5V on the Yun and there are no ill effects.

For dev work, I can temporarily shed some the loads and power everything off USB.

I was thinking of putting a jumper on my shield.
I mostly work with a switching regulator and external power. By having 5V on the 5V and a jumper to select between 5V or +6.5V on Vin I can use the shield for all arduino's.
Best regards
Jantje