More power/heat related problems ...

jamodio wrote:

 

The original post is in spanish. Here is the link ...

http://www.geektopia.es/es/technology/2012/06/22/articulos/se-calienta-el-ordenador-raspberry-pi-estudio-de-sus-temperaturas-en-funcionamiento.html

Excellent, thanks jamodio!  As it happens I'm fairly good with languages and I speak Spanish quite reasonably, so the article made great reading without translation.

That's a really good series of tests made by Remy, and I'll paste one of the images from the article here because it includes the temperature scale on its right-hand side:

This is Remy's thermal image captured with a Fluke Ti35 during H.264 video and AC3 audio playback at 1080p and with Ethernet connected, which yielded the highest temperature recorded, peaking at 65.1C.  It's the first numeric evidence I've seen of the blisteringly high temperature that I've noted (but not measured) on my LAN9512 device.

It would be very interesting to get Foundation engineers' comments on these figures, as so far I think Gert has only commented on subjective observations of "very hot" or finger tests.  Is anyone here not banned yet, and dares post Remy's temperature-labelled image in a hardware thread over there?

Morgaine.

Jorge,

  Is this 1.8V SoC pin issue similar to the floating 1.8V SoC pin issue with the beta boards?

     http://www.raspberrypi.org/archives/470

It sounds to me like maybe they had 2 related problems, but only fixed one.

>I'll put out a warning out there to be carefull on what you put on the GPIO ports and if you use the +3V3 line to supply power to any external circuitry.

I don't know if it's at all related, but abisher reported a mysterious

-3.3V measured between a GPIO pin set to be an output, and ground.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=10198

And perhaps related, Gert explained that a GPIO pin set to be an output

can source as well as sink, resolving a mystery.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=9196

Interesting, I've not seen that comment on the blog about the problem found on the beta boards.

For sure nobody was paying much attention or reviewing the schematics before sending the design to the pcb fab.

Not with the intention to be rude, but I'd not pay much attention at what abisher has to say, in few exchanges I had with him it came out pretty clear that most of the time he does not have much of a clue of what he is talking about, just repeat the message like a parrot, but is fast to aplogize when he realizes he screwed up.

Gert is correct, many GPIO modules on modern microcontrollers and processors can be configured as open collector/drain, which is very handy because you can drive almost anything regardless the power supply to the MCU, but you have to keep in account that whatver current circulates through the load will also circulate or "sink" through the output circuitry of the MCU, so there are current limitations and like any other current circulating through it, it may genearte heat. This is a typical situation with ethernet PHY circuits like the one on the LAN9512, those types of chips are designed to operate somehow "hot" because the differential output drivers sink current that flows through the windings of the ethernet transformer.

But there are ways to use the open drain combined with external driving circuits to handle larger loads without having the MCU to sink excesive currents.

On the other hand if it is not open drain or open collector, you are sourcing the current from the power supply pins to the load, again generating heat on the chip.

In any case, you still need power if you want to put something on the GPIO pins of the R-pi, then where you get that from ?

Depending on the project, I'd strongly recommend to use a separate 3.3V regulator, you can feed it from the main 5V line (asuming that whatever you put won't trigger the

main polyfsue.)

-J

Hi.

How are you?

Please tell me what are the characteristics of the two sheatsinks used.

Thanks