Arduino works only USB-powered, LDO defect?

Other Hardware General Electronics
1

Good evening Guys,

I have a working Arduino System (2 Arduinos communicating via 433). But both of them only work if i plug them into the laptop/PC. If if plug my 7.4 LiPo Battery in Vin/GND, they do not work. Here i measured a Voltage of ~8V. So it should be enough for the extern powersupply.

Also i measure not 5V on the 5V-Pin. It is also 8V, so it looks like the LDO is defect. Could that be the cause of my issue? If i power the Arduino with the LiPo, it only works the onBoard LED, he does not do the code.

Do I need 2 new Arduinos? :open_mouth:

2

Also i measure not 5V on the 5V-Pin. It is also 8V, so it looks like the LDO is defect. Could that be the cause of my issue?

Yes.

Do I need 2 new Arduinos?

If they still work on the USB power then you could just replace the regulator.

3

Also i measure not 5V on the 5V-Pin. It is also 8V, so it looks like the LDO is defect.

Maybe you have a missing ground. Are you measuring 8V between the Arduino's 5V pin and the Arduino's ground? I

If so, your regulators are blown. But in my experience,* blown regulators tend to short to ground when they fail (giving no output voltage) rather than shorting-across (passing-through the applied voltage).

*I've never had an Arduino regulator blow.

4

Rachmaninow:
Also i measure not 5V on the 5V-Pin. It is also 8V, so it looks like the LDO is defect.

Hang on hang on! :astonished:

Are you saying you are measuring eight volts from the 5 V pin to ground on the board? That does not make sense and if it was the case, it is very surprising indeed that the board would work at all afterward on its correct 5 V.

5

Damn... I think the one raduino is now complete defect :confused: He smoked and something exploded when i powered it with the LiPo (8.2V)

The other Arduino:
I measure 8.28V Input. But only 2.8V from 5V pin to GND. I think that is the reason, why the Arduino does nothing. USB-powered it works fine.

I need mobility, so USB is no option to me. Thanks for your help and your suggestions.

6

Again, please explain in excruciating detail.

The only reason - other than a manufacturing defect which is possible, but unlikely - for catastrophic failure of an Arduino when powered with the right voltage (8.2 is fine) in the correct polarity, is if something is incorrectly connected to it.

Do these boards still work or not connected to USB only and no other connections?

If so, check again the voltage on the 5 V terminal.

7

... Like where exactly was the 8V iipo attached to the board?