Re: [DVRPTR_V1] Re: power supply
- This method works well, doesn't bypass/defeat the Pi fuse either.
Note a good hub won't 'back-feed' power from it's 'upstream' port and the Pi's microUSB connector
doesn't have any data connections, it is strictly power only.
upstream|<----<|A,USB Raspberry Pi
USB A|>---->|microUSB power only
HUB B| +------------------------
D|>---->[USB, DVRPTR modem, power]<--- 12vdc
+5|<-- good 5 volt source, 2 or more amps.
The fuse on the Pi is rated 1A, the Pi itself uses approx .7 amps. So even with a hefty power
supply, the Pi can theoretically only supply about .25 A total to the USB ports, that is only about
1/2 of what 1 port should be able to use, so best off to plug any significant load devices into the
This layout above works very well.
-Jim- N1JMM, KB1YPL_B
Visit my Pi running ircddb, dvrptr, Apache & many other things:
On 4/15/13 5:04 AM, Howard Small wrote:
> Does this mean that if I use a 5V 2A powered usb hub with no devices connected directly to the
> dvrptr board (all external devices connected to the dvrptr board via the hub), a usb A to usb B
> cable providing the data link to the board then that would be OK For powering the board? Or is that
> still not recommended?
> On 15/04/2013, at 17:23, "do1fjn" <dvrptr@... <mailto:dvrptr@...>> wrote:
>> Hi Pierre,
>> --- In DVRPTR_V1@yahoogroups.com <mailto:DVRPTR_V1%40yahoogroups.com>, Pierre Martel
>> <petem001@...> wrote:
>> > I know that mine from the german team is running on usb. There was a place
>> > to jump on yhose board to make it run on usb. But that was just if you
>> > wanted to run a hotspot with out the ambe board. Like in a repeater or
>> > such...
>> USB powering is not recommended for repeater / unmanned operation. If you use the board as Hotspot
>> w/o Addons then you can use 5V USB.
>> The weak point of my design is the 78L033 linear voltage regulator - it's a 'normal' part (no
>> low-drop), so for a stable 3.3V it need a good 5V source. USB-Power is sometimes (Hubs) a bit
>> lower: In this case, it's possible that the DV-RPTR do a reset by a small source voltage drop.
>> I tested USB powering with some real HW (Notebooks, PCs) w/o any problems. Using "emulated" poor
>> USB voltage (4.7-4.8V, 100mA) I can force a reset (by ST706T).
>> For PC software (using my open source firmware) it's possible to detect a reset and restore
>> configuration in this case. But I think this feature isn't used in Jonathans or Kurt's software.
>> Jan, DO1FJN
I think the RaspPI is more critical - a good / stable 5V source is needed (>700mA).
If the raspPI works, the 5V source is good enough to feed the DV-RPTR (30mA) too.
The DV-RPTR can't handle 'longer' "brown-outs" (voltage < 4.7V) very well. There is no problem with the (low) current consumption.
Another point are the USB-connectors: The USB-miniAB connector is not so stable like the USM-miniB...