Can I solder 5V to usb input?

Other Hardware General Electronics
1

Hello,

I am working on a project, where I have desisgned a PCD, which uses a DC/DC to convert 28V to 5V.

Now I want to supply the Arduino through its Vin and GND Pins. But if I do so, the Arduino outputs something around only 4.1 V as HIGH, not the desired 5V.

I suggest if I use 5V through the Vin PIN, it is not the same as if I would use the USB's 5V?

So my question is: Can I solder the 5V and GND directly to the USB's GND and 5V wires on the bottom layer of the Arduino, or can this damage either the Arduino or my PCB then?

You can download an picture of my described problem, if you would like to.

Thank you for helping me!

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2

The Vin goes into a 5v regulator so 5 volts will be reduced. It is capable of handling 7.5 v to around 20v. Recommend range is 7.5 to 12v. Best is around 9v.

You may be able to set your DC/DC converter to 9v.

Weedpharma

3

Yes I have found out this, too. But the PCB is already produced and any IC I would like to change, would take many changes...
So I would like to find a way to use the 5V I already have. Is soldering an option?

4

Soldering is always an option as 5v is 5v. It depends on your soldering ability.

Weedpharma

5

OK.

I simply wasnt sure if my laptop's 5V output is different than my DC/DC's 5V output.
So the supply via USB is differently processed (electrically), than via Vin. Is this correct?

So if noone says soldering directly on the bottom to the USB's GND and 5V is risky, I will do it this afternoon.
Thanks in advice!

6

"So the supply via USB is differently processed (electrically), than via Vin. Is this correct? "

5v from USB is regulated from the PC. As it is already 5v, it is supplied direct to the electronics.

Weedpharma

7

USB 5V goes thru a resettable fuse to protect the PC if the device tries to draw more.
Do not supply external 5V when PC is connected - the external may end up supplying 5v into the PC and may cause problems.

8

Sounds like you are new to this stuff.

Use the board the way it was designed.
Power the board using the power jack minimum of 7 volts.
Or
Power it from the PC via the USB.

If you power it any other way you WILL eventually forget what's what and you WILL damage something.

9

I think OP has a custom board Larry.

10

Yes, you can supply 5V directly to the USB socket if you wish. Or to the pin labeled "5V" in the Power section.

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11

Now I want to supply the Arduino through its Vin and GND Pins. But if I do so, the Arduino outputs something around only 4.1 V as HIGH, not the desired 5V.

Sorry, I thought they were using an standard Arduino.

12

The Vin pin goes to a linear regulator. It is the same as plugging an adapter into the barrel connector jack.

So if you put 5V into it, the regulator drops out some voltage and the 5V line on the Arduino will be less than 5V.

Put 5V into the pin labeled 5V. It bypasses the regulator.

13

I've externally powered my arduino thru the arduino 5v pin using a 7805 regulator chip. Try using the 5v pin first, then solder at other points if the regulator board works.