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Old 17-08-2019, 19:27   #1
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power for Pi B+

Why does the system run fine on a 2.5 amp power brick but flash the low power lightning bolt when run off of a 3 amp 12-5 V transformer? I want to avoid turning DC into AC and back into DC.
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Old 17-08-2019, 20:07   #2
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Re: power for Pi B+

Have you measured the actual loaded output voltage of the PS?
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Old 17-08-2019, 20:44   #3
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Re: power for Pi B+

Try another converter. I use a 12->5VDC 5amp unit that runs both a 3B+ and 5 port switch with no problem at all.


I should have added, the 3amp converters do seen to have a problem running the RPi. I experienced the same issue during testing.
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Old 18-08-2019, 11:35   #4
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Re: power for Pi B+

My bet is the 3 amp converter is a cheap Chinese item and they lie about the specs on most things they sell.
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Old 18-08-2019, 11:53   #5
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Re: power for Pi B+

I've been having good results from these guys. My Pi test bench has one. One of these powers 4 USB jacks on our boat.

Given that the Pi's don't like having their power just cut off (it sometimes corrupts the SD card), you might consider getting one of those USB power packs for the Pi, and using a 12-5 converter to keep that charged.
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Old 18-08-2019, 11:56   #6
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Re: power for Pi B+

Been running my pi for more than a year using a dc-dc 12v->5 from Amazon... Direct wired to gpio. No issues... Very happy... Also have a similar boost converter running my monitor.

One time I did get lightning bolt was due to connection.. Remove, spray and back to normal..

Is your converter adjustable? Confirm output voltage with a multimeter..
Good luck

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Old 18-08-2019, 14:11   #7
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Re: power for Pi B+

You have not provided enough information to answer fully:


What was your 12v system voltage?
What make and model of the two devices in question (ideally with links to their data sheets so that I don't have to go searching)?
What peripherals do you have attached to the Pi (again make and model and links to data sheets)?


Depending on the design of you DC/DC converter the output may not be stabilised but follow the input and if it is an automotive targeted product it will be looking for 13.8V - 14.4 V on the input. Does it get warm? Do you still get the low power warning when you are running your engine with the alternator putting out 13.8 - 14.4V?
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Old 19-08-2019, 01:11   #8
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Re: power for Pi B+

Quote:
Originally Posted by Moo View Post
You have not provided enough information to answer fully:


What was your 12v system voltage?
What make and model of the two devices in question (ideally with links to their data sheets so that I don't have to go searching)?
What peripherals do you have attached to the Pi (again make and model and links to data sheets)?


Depending on the design of you DC/DC converter the output may not be stabilised but follow the input and if it is an automotive targeted product it will be looking for 13.8V - 14.4 V on the input. Does it get warm? Do you still get the low power warning when you are running your engine with the alternator putting out 13.8 - 14.4V?
I am using stabilised and isolated power supply from Main Well. These are available in a lot of specifications.

Works very good. Voltage can be slightly adjusted for the RPI. Mine RPI4 running on 5,1 volt. These power supplies are also rather cheap and almost everywhere available. 12 - 5 volt cost around € 25,-

https://www.meanwell.com/webapp/prod...spx?prod=SD-25

Regards,


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Old 19-08-2019, 03:27   #9
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Re: power for Pi B+

Quote:
Originally Posted by verkerkbr View Post
I am using stabilised and isolated power supply from Main Well. These are available in a lot of specifications.

Works very good. Voltage can be slightly adjusted for the RPI. Mine RPI4 running on 5,1 volt. These power supplies are also rather cheap and almost everywhere available. 12 - 5 volt cost around 25,-

https://www.meanwell.com/webapp/prod...spx?prod=SD-25

Regards,


Bram

I meant that the OP who has the problem should post so that I and others can provide more targeted suggestions as to what the problem might be.
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Old 19-08-2019, 05:18   #10
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Re: power for Pi B+

The input voltage must be between 4.75 and 5.25 volt (loaded).

Use a more short and thick cable because long cables decrease voltages.
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Old 19-08-2019, 05:30   #11
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Re: power for Pi B+

Quote:
Originally Posted by isladelobos View Post
The input voltage must be between 4.75 and 5.25 volt (loaded).

Use a more short and thick cable because long cables decrease voltages.
These cheap usb cables are mostly too thin. I have cut the original power supply cable in two and use the part with connector to power the RPI. Then you see de difference between the cables.

That is main cause for this problem.
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Old 20-08-2019, 09:37   #12
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Re: power for Pi B+

I also have the Mean Well converter for Pi with Montessier HAT and M.2 SSD HAT.
Two good quality power cables.

Runs fine for over a year now.
SSD much faster as SD card, and no problems with corrupt SD Card.
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Old 23-08-2019, 08:06   #13
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Re: power for Pi B+

This may be a alternative?
Unfortunately not for 12 V (4.2V - 10V)
https://www.electrokit.com/en/product/pijuice/
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