Raspberry Pi just assembled

It is important that the board is getting at least 4.75v on the board. I got my Pi on Thursday and after loading the image onto the SD card using my Mint Linux machine I placed the card into the socket on the PI (had mouse, keyboard, monitor and ethernet hooked up) and plugged in my power. The board came up just fine and while it was booting up I measured the DC on the board itself, I got 4.87v which is low but ok. I'll probably just build a small 5.25 V supply to make sure I'm getting 5v on the board.

As soon as it booted it went out and found any updates all by itself, also I was offered the option of using the whole 8GB SDHC card instead of the 2GB partition so now I have plenty of room for programs and files. Hell my old Toshiba TSE1000 only had 1MB of ram and two floppy disks on it and that was plenty for that era.

Bob

Bob Cleary wrote:

 

It is important that the board is getting at least 4.75v on the board. I got my Pi on Thursday and after loading the image onto the SD card using my Mint Linux machine I placed the card into the socket on the PI (had mouse, keyboard, monitor and ethernet hooked up) and plugged in my power. The board came up just fine and while it was booting up I measured the DC on the board itself, I got 4.87v which is low but ok. I'll probably just build a small 5.25 V supply to make sure I'm getting 5v on the board.

IMO, 4.87V is plenty for the RasPi, with good margin.  My own RasPi works down to 4.65V.  It really depends on your peripherals: if they work fine at 4.87V there's really no need to increase it to 5.0V.

Since 3.3V regulator RG2 is a linear regulator, you're better off with 4.87V instead of 5.0V: RG2 won't run as hot with 4.87V input.

Good point, does that mean the bulk of the current is used by the 3.3v portion?

Years ago I worked with stack computer boards (3" sq) that got very flaky below 4.80v and the supply for them was about 5 ft away and they did not bother to use remote sense, it took a good 30 minutes to get that supply out so you could tweak the pot up so you could have alittle margin to play with.

I'm using a usb charger I bought from TigerDirect that has two 0.5a and a single 1a ports on it, the lead they supplied is pretty thin but so far it works well.

Bob Cleary wrote:

 

Good point, does that mean the bulk of the current is used by the 3.3v portion?

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I'm using a usb charger I bought from TigerDirect that has two 0.5a and a single 1a ports on it, the lead they supplied is pretty thin but so far it works well.

You can find the RasPi schematics at http://elinux.org/Rpi_Hardware#Schematic_.2F_Layout.  To save cost, I believe all of the voltage regulation on RasPi uses linear regulators, except for the SoC core voltage which has an internal switching regulator using an off-chip inductor.  So except for the SoC core, each X mA used by a given voltage requires X mA of 5V.  All of the current goes through 3.3V regulator RG2, which gets warm.  USB and HDMI peripherals use 5V, so they don't warm RG2.

You might see if you can find a Micro USB cable with larger conductors.  However, it's usually impossible to tell in advance, especially with mail order.

Everything is working fine,have not checked the voltage as yet.....many thanks for the comments.

Regards...John

Everything is working fine,have not checked the voltage as yet.....many thanks for the comments.

Regards...John