myNameIsFred123
Posts: 3
Joined: Sun Sep 05, 2021 9:52 pm

Fried Pico with External Power Supply

Sun Sep 05, 2021 10:03 pm

Hi, I got a pico a few days ago and have been experimenting with it. Up until today I've just been powering it via the micro-usb port from my laptop's usb. Today I attempted to power the pico with a 5v 3amp wall wart (verified voltage with multimeter) and the pico let go of its magic smoke. He's dead. I followed the data sheet's recommendation to power the pico via the VSYS pin. I connected the 5v power supply's positive to the VSYS, and the negative to the ground pin just below the VSYS, and this killed the pico. Did I misunderstand the datasheet here?


Thanks

ex_piro
Posts: 9
Joined: Sun Jul 18, 2021 10:32 am

Re: Fried Pico with External Power Supply

Mon Sep 06, 2021 12:10 am

That all sounds like you're doing it right, assuming you didn't have both the power supply and your pc connected at the same time. I use cheap USB chargers to power my development pico and it's been running for months on that. The only difference is I have a diode between the VSYS pin and the power supply so I can also plug in my pc at the same time. The pico is not tolerant of over voltage, anything over 5.5V will probably fry it in short order. One thing to check is that your wall wart is not putting out any AC voltage along with the DC. Your multimeter will not pick that up when measuring DC voltage. It will give you the average voltage. Check it with your meter on AC volts and see if your have an AC voltage on the output. I suspect the power supply as a more likely cause than a problem on the pico board, especially since it ran fine on the USB power.

myNameIsFred123
Posts: 3
Joined: Sun Sep 05, 2021 9:52 pm

Re: Fried Pico with External Power Supply

Tue Sep 07, 2021 7:28 pm

ex_piro wrote:
Mon Sep 06, 2021 12:10 am
That all sounds like you're doing it right, assuming you didn't have both the power supply and your pc connected at the same time. I use cheap USB chargers to power my development pico and it's been running for months on that. The only difference is I have a diode between the VSYS pin and the power supply so I can also plug in my pc at the same time. The pico is not tolerant of over voltage, anything over 5.5V will probably fry it in short order. One thing to check is that your wall wart is not putting out any AC voltage along with the DC. Your multimeter will not pick that up when measuring DC voltage. It will give you the average voltage. Check it with your meter on AC volts and see if your have an AC voltage on the output. I suspect the power supply as a more likely cause than a problem on the pico board, especially since it ran fine on the USB power.
Hi, thanks for confirming that my connection from the power source is right! At least I can rule that out now. I'll eventually order another pico, and just don't wanna fry the next one in the same fashion. I checked the AC voltage on my wall wart and its reading 0.007 volts. I didn't know that getting AC voltage through these wall warts was a thing. Thanks for shedding that light. I'll definitely keep that in mind in the future. I've used the same wall wart on other boards, like the Seeeduino Xiao and an Arduino Uno, without problems. I'm thinking I must've hooked up something wrong when attempting to power the Pico. Is it possible that 0.007V AC fried it? Oh well, at least at $4 its not a big loss. Thank you for the help!

trejan
Posts: 3715
Joined: Tue Jul 02, 2019 2:28 pm

Re: Fried Pico with External Power Supply

Tue Sep 07, 2021 7:51 pm

myNameIsFred123 wrote:
Tue Sep 07, 2021 7:28 pm
Is it possible that 0.007V AC fried it?
No. That is mains hum and everywhere. Your wallwart doesn't have any significant AC output.

lurk101
Posts: 965
Joined: Mon Jan 27, 2020 2:35 pm
Location: Cumming, GA (US)

Re: Fried Pico with External Power Supply

Tue Sep 07, 2021 11:33 pm

myNameIsFred123 wrote:
Tue Sep 07, 2021 7:28 pm
I checked the AC voltage on my wall wart and its reading 0.007 volts.
Otherwise called ripple. Perfectly normal and of no concern.

myNameIsFred123
Posts: 3
Joined: Sun Sep 05, 2021 9:52 pm

Re: Fried Pico with External Power Supply

Thu Sep 09, 2021 2:39 am

trejan wrote:
Tue Sep 07, 2021 7:51 pm
No. That is mains hum and everywhere. Your wallwart doesn't have any significant AC output.
lurk101 wrote:
Tue Sep 07, 2021 11:33 pm
Otherwise called ripple. Perfectly normal and of no concern.
This makes sense. One thing I observed when checking the AC voltage on the DC power supply is that the multimeter reads a higher AC voltage when the probes aren't in contact with anything (aside from the air). It actually reads ~0.040V just ambient voltage in the air, and hooking the probes to the DC power supply's output actually drops that down to 0.007V.

Fascinating...

User avatar
penitko
Posts: 16
Joined: Thu Jun 10, 2021 9:25 am
Location: Finland, Vantaa

Re: Fried Pico with External Power Supply

Fri Sep 17, 2021 6:22 am

ex_piro wrote:
Mon Sep 06, 2021 12:10 am
The only difference is I have a diode between the VSYS pin and the power supply so I can also plug in my pc at the same time.
1)
What kind of diode do you have and is it forward or reverse connected ?

2)
In that way, when the voltage supply is not taken from the USB connector, can the USB connection still be used for data transfer with D+ and D- pins?

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