Power via 5v rail

Official Hardware Mega GIGA R1 WiFi
1

Is it possible to power the Arduino Giga by sending 5v directly to the 5v power rail?

PIN: 5
Description: +5V Power +5V Power Rail

I have an existing shield for a Arduino Uno R3/R4 that sends 5v to this pin. This seems to work just fine for the Uno. Again to emphasize the shield is sending 5v to the 5v power rail pin and not the VIN. Looking at the schematics for the Uno and Giga, this should be fine as it's simply skipping the buck converters that step the variable voltage that can be supplied on the VIN pin to 5v.

2

Sounds risky. The Giga runs at 3.3 V, this way you will back feed 5 V through the 5 V regulator into the 3.3 regulator.

At stake: the 5 V regulator.

If you try, come back and tell us whether the magic smoke was released or not :wink:

3

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It definitely does not skip the 3.3v converter see the official Arduino diagram. It does go against the arrows. I see the same depiction in the Uno and have not encountered any issues yet.

4

I missed that one, good call. Well then, from what I can see in this diagram you're good to go.

:+1:

5

In either case will report back once I test it out.

6

Hi @spielp,

I wouldn't recommend you power the board using the 5V out PIN since it is designed to be a voltage output:

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It has a protection Schottky diode but I still do not recommend you input voltage in that PIN.

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I recommend you input the voltage using the VIN pin instead, which has been designed for this purpose.

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I hope this helps you to clarify it :slight_smile:

7

It's not skipping them; it is applying 5V to their output - ie, feeding them "backwards".

8

It = the 5 V or the VUSB?

9

@awneil @jorgetrujilloroman

From my understanding the recommendation against power an Arduino through the 5V pin is that if something is connected to the VIN pin that sinks current, i.e with a lower voltage potential than 5V, it can hurt or destroy the voltage regulator through the backward diode inside. In the Giga, there's a converter, and I can't say if there's a corresponding sub-circuit. Lets assume there is.

To power an Arduino with 5V will not automatically destroy the regulator / converter. It will only happen if you have something that sink current from VIN, which only happens if something is connected to the VIN with less than 5V (not counting the the Vf of the built-in diode). And the USB is protected by the diode.

So accordingly to the schematics / diagram, there's little risk.

10

It’s not as simple as sending it to VIN as the shield has its own voltage converter that drops incoming voltage from 24v to 5v that is then feed to the Arduino and to another converter that drop the 5v to 3.3v. The 3.3v is used for something else not by the Arduino. A couple of issues. The VIN says that input voltage should be a minimum of 6v, in my case the shield only supplies 5v.

11

Is the shield always sourcing 5V, or is it optional?

12

Currently the shield is providing 5v.

I would like the shield to be usable both on the Giga and Uno R4 minima. Looks like both boards can deal with VIN of 24v as both are using buck converters. I was previously using this shield with Uno R3 which had an upper limit of 20v on the VIN, thus the presence of the converter on the shield in the first place. I could get rid of the converter on the shield all together and just pass 24v to the Uno R4 minima and Giga boards directly.

Would it at all be beneficial to feed these boards with a lower voltage?

1 Like