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mahjongg
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Re: voltage and polyfuse

Sat Aug 18, 2012 2:29 pm

kerml wrote: I think that 0.6 ohm is too low and it could be damaged!
Any one can give me a second opinion?
0.6 ohm isn't "too low", (saying its too low is contradictory) in fact if its "damaged" (in the sense it has recently been blown) it should be too high, not too low, also polyfuses are self repairing although they never completely recover.

Also 4.82 is completely normal, so unless you PSU has a lot of ripple on its 5V it should be fine.

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kerml
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Re: voltage and polyfuse

Sat Aug 18, 2012 2:48 pm

But why I have to connect the PS two times to the rpi boot?

Could be a SD card problem?
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mahjongg
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Re: voltage and polyfuse

Sat Aug 18, 2012 3:12 pm

I would say start another thread in the troubleshooting section with that fault description.
Use: "Why do I have to power up the RPI two times to boot?"

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kerml
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Re: voltage and polyfuse

Tue Aug 28, 2012 8:33 pm

mahjongg wrote:I would say start another thread in the troubleshooting section with that fault description.
Use: "Why do I have to power up the RPI two times to boot?"
You are right!
But my rpi is working!
And I need another one.
I will buy a new one and use a different sdcard manufacturer and also a different power supply.
Then I can switch cards and the PS and see the effect on the first rpi.
Amor de Slackware
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Re: voltage and polyfuse

Tue Aug 28, 2012 8:42 pm

I'm glad your PI is working (my thought == "Mission accomplished"!).

then, every problem is an opportunity to learn....

If you buy another one, chances are good that you will get one with the offending 140mA fuses removed, so you will see no nonsense with "limited to 100mA devices only" (unless your PSU is a piece of s**t, and collapses to 4.6 volt under the load, that is, but that is indeed -another- issue).

Maybe your original card will be fine, especially if you use the latest firmware, SD-card compatibility also improves with leaps and bounds.

If you have two pie's you have so much more opportuniteit to test things, its true!

Have fun with your pi's. :P

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kerml
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Re: voltage and polyfuse

Tue Aug 28, 2012 9:02 pm

How I can get info about

"offending 140mA fuses removed"

when buying the rpi?
Amor de Slackware
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Lob0426
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Re: voltage and polyfuse

Wed Aug 29, 2012 7:01 pm

kerml wrote:How I can get info about

"offending 140mA fuses removed"

when buying the rpi?
No real info available, but the newest RasPi are showing up with 0 ohm resistors in place of the 140ma fuses. This is a recent production change.
512MB version 2.0 as WordPress Server
Motorola Lapdock with Pi2B
Modded Rev 1.0 with pin headers at USB

http://rich1.dyndns.tv/
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Re: voltage and polyfuse

Thu Aug 30, 2012 4:39 am

I power my Pi through GPIO and I've short circuited the USB polyfuses. I get 5.1 volts pretty much everywhere no matter what I connect to the USBs ( I wouldn't push it as far as a 2.5" HDD ). I can plug webcams and heavy keyboards in and out and the Pi keeps going. I have a deep mistrust of phone chargers........
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

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Re: voltage and polyfuse

Thu Aug 30, 2012 6:36 am

Lob0426 wrote:
kerml wrote:How I can get info about

"offending 140mA fuses removed"

when buying the rpi?
No real info available, but the newest RasPi are showing up with 0 ohm resistors in place of the 140ma fuses. This is a recent production change.
Well.... *Some* of the new ones to show up have 0 ohm resistors in place of 140 mA polyfuses. The two I received today have polyfuses.

I will see what shows up in the (estimated) 7 weeks for next to arrive.

stanley
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Re: voltage and polyfuse

Wed Mar 13, 2013 5:22 am

Hi,
My Pi is still reading 3.9 to 4.0V on TP1/TP2 after I let it cool off for like 12hrs..

I tested with the following results :-

F3 polyfuse is 0.6 Ohm

Belkin 4-port hub, 2.6A, 5V :
outside : 4.57V
inside : 4.0V

Apple iphone charger. 1.0A :
outside : 4.75V
inside : 4.0V

TP-Link Hunt-Key ( low ripple adapter ), 1.0A :
outside : 5.04V
inside : 4.0V

Is this board okay or faulty or I still have to "wait" longer for the F3 polyfuse to cool off..

Mine is a rev 2.0 without any polyfuse on F1 & F2
Stanley
blog :- http://arduino-for-beginners.blogspot.com/
fb group :- https://www.facebook.com/groups/arduino.for.beginners/

obcd
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Re: voltage and polyfuse

Wed Mar 13, 2013 7:21 am

Even your outside voltage readings are low.
This might indicate that your Pi is consuming 2 much current.
It would also explain why the Polyfuse has such a high voltage drop.
To be sure about this, you would need to measure the Pi current, preferable when it's powered from
the gpio 5V and GND pin's. If it's higher than 300 - 500mA you're Pi is defective.

stanley
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Re: voltage and polyfuse

Wed Mar 13, 2013 8:06 am

obcd wrote:Even your outside voltage readings are low.
This might indicate that your Pi is consuming 2 much current.
It would also explain why the Polyfuse has such a high voltage drop.
To be sure about this, you would need to measure the Pi current, preferable when it's powered from
the gpio 5V and GND pin's. If it's higher than 300 - 500mA you're Pi is defective.
Thanks for the reply... it measured 200mA with nothing connected and the polyfuse had recovered.. my Pi is back to normal now...
Stanley
blog :- http://arduino-for-beginners.blogspot.com/
fb group :- https://www.facebook.com/groups/arduino.for.beginners/

obcd
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Re: voltage and polyfuse

Wed Mar 13, 2013 8:37 am

Good to hear.
Are you willing to share what tripped the Polyfuse in the first place?
(To prevent others from doing the same)

stanley
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Re: voltage and polyfuse

Wed Mar 13, 2013 2:15 pm

Are you willing to share what tripped the Polyfuse in the first place?
(To prevent others from doing the same)
I used to run the below setup overnight without any issues until this time only...

My setup as follows, RPi running Adafruit Occidentalis v0.2 with nRF24L01+ on SPI and Bluetooth modules connected to RPi console port...

Power supply is 5V 2.6A Belkin F4U040 powered 4-port USB hub with a Asus N10 wireless adapter connected...

To monitor the operating voltage, I have this http://www.myduino.com/index.php?route= ... uct_id=169 voltage meter connected to TP1/TP2 all the time...

I'm mainly testing/developing the nRF24L01+ RF modules...
Stanley
blog :- http://arduino-for-beginners.blogspot.com/
fb group :- https://www.facebook.com/groups/arduino.for.beginners/

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