[foldr]

>Yeah, and microSD cards run at 3V3.

Err, yes. Hence the LDO regulators.

>The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3.

The RPi has filtering capacitors. In general filtering capacitors are regular cheap X5R or X7R caps. They don't need to be anything special. Look at any LDO regulator datasheet.

> Oh, and people usually buy the 2-5$ range of power adaptors from Amazon

What does that have to do with the designers of the RPi? They don't have any control over which power supplies people buy.

[paulmd]

> The RPi has filtering capacitors

It's hard to specifically assign blame to noise since it's such a personal and transient problem, but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering and if anything is doing things that are much more sensitive to noise due to its OS.

http://www.crazy-audio.com/2013/09/raspberry-pi-power-supply...

> What does that have to do with the designers of the RPi? They don't have any control over which power supplies people buy.

You shouldn't have to buy a power supply at all. The norm is that when you buy a piece of hardware it comes with an appropriate power supply. When I buy a $15 gigabit-ethernet switch from D-Link, it comes with a power adapter.

Again, the Pi Foundation wanted to hit their price target so they could put "A computer for $35!!!" in their advertising, so they cheaped out on something that probably costs $2 when you are buying a million of them. At quantity 500, you are already down to $4 when sourcing them from Mouser.

They also pretty much openly encouraged you to use whatever crappy USB charger you had lying around. The reality is most knockoff chargers are total crap, their current ratings are dramatically overinflated, and they certainly won't be delivering clean power anywhere near their current ratings, which again amplifies the problems with the Pi's lack of filtering.

All of this has been well-known for ages. Check out Ken Shirriff's excellent series of teardowns on cheapo USB chargers and his comparison to a genuine Apple charger. This was not news even at the time.

http://www.righto.com/2012/03/inside-cheap-phone-charger-and...

http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-ap...

http://www.righto.com/2012/05/apple-iphone-charger-teardown-...

[foldr]

>but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering

What is your source for all these statements? How do the voltage regulation circuits in phones differ? If anything the phones ought to have more noise, since they're using switching regulators rather than linear regulators.

>Again, the Pi Foundation wanted to hit their price target

Yes, you got it. There's 1001 improvements that could be made to the RPi. If you made all of those improvements, it would not be affordable.

>They also pretty much openly encouraged you to use whatever crappy USB charger you had lying around.

They say to use a charger that's rated for at least 2.5A. That does not include most crappy phone chargers. They also sell an official RPi power supply which anyone is free to buy if they're concerned about this issue.

[paulmd]

> What is your source for all these statements? How do the voltage regulation circuits in phones differ? If anything the phones ought to have more noise, since they're using switching regulators rather than linear regulators.

It's pretty self-evident that the circuits are different. The phone normally operates from its battery, the amount of ripple present from a battery is zero. I'm not sure what source exactly you want me to provide to cite the fact that a phone has a battery, anyone knows that.

Also, typically a phone will use a buck converter (or perhaps buck-boost) to drop its voltage, rather than a switching regulator.

Some phones do have problems operating while plugged into crappy adapters (the power does pass through), the most common being that the touchscreens stop working.

> Yes, you got it. There's 1001 improvements that could be made to the RPi. If you made all of those improvements, it would not be affordable.

And yet any network switch you buy off the shelf for $15 comes with a workable power supply.

But yes, that is my point, the parent was asking for reasons why you wouldn't buy a Raspberry Pi, and the fact that it's got a shitty power system that tends to result in SD card corrupt is a major reason you should not purchase a Pi and prefer a properly engineered product. I think we're in agreement.

The Pi Foundation themselves cite the cost of the switching-mode power supplies on their alpha boards as adding $2 to the bill-of-materials cost, leading to their decision to remove them from production boards. Terrible anti-consumer move, how much have you spent on burned-out SD cards so that they could hit their $35 price point?

https://www.raspberrypi.org/blog/power-supply-confirmed-as-5...

Anyway, any random piece of electronics comes with a power supply. A $15 network switch comes with a power supply, or a drive enclosure (those are even quite beefy ones!). Competing products like the ECS Liva come with their own power supplies too, and the total cost of the system is the same as the Pi.

> They say to use a charger that's rated for at least 2.5A. That does not include most crappy phone chargers.

They've backpedaled on this since the launch after problems started appearing. The official spec at launch was that the Pi pulled 700ma for Model B and 300ma for Model A, and pretty much any random charger meets that spec. Anyway, most chargers are significantly overstating the amount of clean power they can provide, because they expect the phone to be using them for charging, not for operating.

You can see the original statement from the Pi Foundation here: https://www.raspberrypi.org/blog/power-supply-confirmed-as-5...

And then after launch they started realizing they had problems: https://www.raspberrypi.org/forums/viewtopic.php?f=2&t=5420

> I'll be testing PSUs soon as well, although maybe not as thoroughly. It certainly seems that the Foundation may have been wrong in assuming that USB chargers produce the current they say they do and that all USB cables are reasonably constructed.

The fact that $1.99 adapters you get off eBay were built like shit wasn't a shocker to anyone, even at the time. That's a hilariously naieve assumption for them to make.

> They also sell an official RPi power supply which anyone is free to buy if they're concerned about this issue.

This only launched within the last year. Good on them for finally doing it, but it should be included with the device, and should have been included from day 1.

http://www.electronicspecifier.com/power/stontronics-manufac...

[foldr]

> The phone normally operates from its battery, the amount of ripple present from a battery is zero. I'm not sure what source exactly you want me to provide to cite the fact that a phone has a battery, anyone knows that.

I was asking for a cite on the claim that the phone has a better voltage regulation circuit. AFAIK both the RPi and phones are using jellybean switching regulator ICs to convert and regulate the voltage. Even an expensive switching regulator is going to have a hard time competing with the PI's linear regulators in terms of output noise. (The Pi, of course, can afford to waste a bit of power, whereas the phone needs to juice all of the battery capacity.)

>Also, typically a phone will use a buck converter (or perhaps buck-boost) to drop its voltage, rather than a switching regulator.

Erm, a buck converter is a kind of switching regulator (one that drops rather than increases the voltage). See for example the buck/boost/etc. options under 'Topology' in Mouser's switching regulator category, or the Wikipedia definition:

http://www.mouser.co.uk/search/refine.aspx?N=10368713

https://en.wikipedia.org/wiki/Buck_converter

>Some phones do have problems operating while plugged into crappy adapters (the power does pass through), the most common being that the touchscreens stop working.

This undermines your point that phones somehow have better voltage regulation circuitry than the RPi. Many that will run directly off USB power have exactly the same issues.

>Good on them for finally doing it, but it should be included with the device, and should have been included from day 1.

But why are you still advising people not to buy the Pi because of power supply issues? I bought my first Pi a few months ago and made sure to get an adequate power supply (not difficult). I haven't had any problems.