Too high voltage? (PSP PSU 5.4 V)

[S10QaN]

Hi,

I have 5 PSP power supply units laying around, so I made a USB plug at the end of one of the chargers.

I tested the PSU at forehand, and I got 5.42 V, also while connecting a resistor in seriel (auto adjustment?).Why is this?


I tried to plug it in the RPi and I measured 5.31 V over TP1 and TP2. The RPi was not connected to anything, not even a SD card. So maybe the voltage will be lower with load.

So my question is regarding the high voltage, is it safe for the RPi? Remember that this was measured over TP1 and TP2.

In the Wiki I read that the RPi will run well of 4 AA batteries, but that have to be with a regulator, right? 4 AA batteries would output 1.6 x 4 = 6.4 V. Is the regualtor on the RPi up for the job to regulate such high voltage down to ~5 V?

The PSP charger seems like a solid power supply for the RPi though, delivering stable (maybe too stable) 5+ V (actually 5.3 V). Should I modify it to deliver closer to % V output?

Sorry for my messy English, I guess I am excused as I am from Norway!.

Thanks in advance.

[mahjongg]

The "works with four AA-batteries" story was only ever really true with one of the first beta boards, which featured a 5V low drop regulator.

Officially 5.25 is the maximum for most "5V logic" devices (5V +5%) with 4.75 (5V - 5%( as minimum, but the PI (or rather its USB peripherals) seem rather more comfortable with a minimum of 4.8 Volt.
If a "5V supply" has an unloaded output voltage that is much higher than 5% over nominal, then its probably very badly regulated, and the designers are anticipating a rather dramatic drop when you load the thing, not good for a PI!

I don't think the PI will drop dead if you apply 5.4 Volt, but attached peripherals might be more sensitive, but no doubt this voltage will collapse when you draw a few 100mA.

[S10QaN]

I somehow posted this thread 2 times, here's the link to the other one: http://www.raspberrypi.org/phpBB3/viewt ... 95#p155595

The "works with four AA-batteries" story was only ever really true with one of the first beta boards, which featured a 5V low drop regulator.

Officially 5.25 is the maximum for most "5V logic" devices (5V +5%) with 4.75 (5V - 5%( as minimum, but the PI (or rather its USB peripherals) seem rather more comfortable with a minimum of 4.8 Volt.
If a "5V supply" has an unloaded output voltage that is much higher than 5% over nominal, then its probably very badly regulated, and the designers are anticipating a rather dramatic drop when you load the thing, not good for a PI!

I don't think the PI will drop dead if you apply 5.4 Volt, but attached peripherals might be more sensitive, but no doubt this voltage will collapse when you draw a few 100mA.

Thanks for your reply. I think I'll investigate this further when I get more parts. I probably will power a USB hub with this also, so I hope I can get it down to 5.25 V (unloaded) so it stays around 5 V (or a bit over).Many PSUs goes too low (voltage) when the load increases, because of the cables and internal resitance and different quality on the PSU.