[hpsdr] LPU Capacity

Wed Dec 28 15:08:58 PST 2011

Hi Pete,

The 5VSB pin is +5 Volt standby power, used to power things like the 
NIC (for wake on LAN) and the power on-off switching circuitry that 
has to be always active in the PC. It is not used (or even 
distributed over the Atlas bus) by any HPSDR boards.

The picoPSU is a good choice, but it is a bit RF-noisy.  The reason 
that it is so small and runs so cool is that it is a switch-mode 
power supply (SMPS) as opposed to the LPU, which is a linear power supply.

The 5V regulator on the LPU is rated at 2A continuous, but the pico 
fuses are not. When you get up towards the maximum rating of the 
regulator, the fuses will trip (and reset, and trip, and...). This is 
the reason for the LPU errata suggesting that you remove them from 
the circuit (short them out).

73,
Scotty WA2DFI

At 14:04 2011-12-28 -0500, n3evl wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>
>A couple of months ago I decided to retire LPU in favor of the 
>picoPSU-120-WI-25.  This appears to fulfill the current requirements 
>of the usual suspects + Metis at 1 Gigabit. The picoPSU spec quotes 
>two figures for 5V:
>
>5V 6A
>5VSB 1.5A
>
>I have no idea what 5VSB refers to - maybe somebody can shed some 
>light on this designation?
>
>The picoPSU unit is quite small and does not have the tall heatsinks 
>used with LPU.   It supposedly runs quite a bit cooler but I left 
>the fan in place figuring some air flow through Pandora can't hurt.
>
>Pete, N3EVL
>
>On 12/28/2011 10:03 AM, Chris Day wrote:
>>
>>***** High Performance Software Defined Radio Discussion List *****
>>
>>
>>
>>Thanks, Erich. Replacing the soft fuses with wire has been enough 
>>so far, but I haven't fired up the transmitter section of Pennylane 
>>yet. Linear chain will be external, so there will be no extra load 
>>from that. Meanwhile, playing with Mercury with delightful results.
>>
>>Chris Day
>>AE6VK
>>
>>
>> > Date: Wed, 28 Dec 2011 04:12:10 -0800
>> > From: <mailto:vk5hse at yahoo.com>vk5hse at yahoo.com
>> > To: <mailto:hpsdr at lists.openhpsdr.org>hpsdr at lists.openhpsdr.org
>> > Subject: Re: [hpsdr] LPU Capacity
>> >
>> > ***** High Performance Software Defined Radio Discussion List *****
>> >
>> > Have cobbled together various reflector postings for my own 
>> reference as well as for others.
>> >
>> >
>> > There was a summary posted to the reflector that is worth reviewing:
>> >
>> > 
>> <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2011-March/014678.html>http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2011-March/014678.html
>> >
>> > the meaty bits were:
>> >
>> > Magister = Ozy
>> >
>> >
>> > power consumption summary:
>> >
>> >
>> >                        12 V         5 v
>> > OZY               .001  A        .1 A
>> > PENY             .4 A           .2 A
>> > MERC            .2  A          .5 A
>> >
>> > Metis 100                         .4A
>> >
>> > Metis 1000bT                   .75A
>> >
>> >
>> > no-one seems to have stated excalibur power requirements, but it 
>> doesn't appear to be huge
>> >
>> >
>> > add the LPU errata document:
>> >
>> > 
>> <http://www.tapr.org/pdf/LPU_Errata.pdf>http://www.tapr.org/pdf/LPU_Errata.pdf
>> >
>> > which mentions in errata #2:
>> >
>> > "Description of Error:
>> > Fuses F2 and F3 are underrated for a full system. They are rated 
>> at continuous 1.1A without
>> > tripping, while an Ozy/Mercury/Penelope system draws typically 
>> 1.3A from the +5V rail.
>> >
>> >
>> > Symptoms:
>> > An Ozy/Mercury/Penelope system will operate for a short period 
>> and then unexpectedly shut
>> > down. The time can vary, but is typically around 10 minutes. 
>> This is due to F2 opening and shutting
>> > down the +5V output. (Note that F2 doesn't actually "open"; it 
>> becomes higher resistance to protect
>> > the load.) After a power cycle, normal operation resumes.
>> >
>> >
>> > Recommended Corrective Action:
>> > Short across F2 and F3 with pieces of wire."
>> >
>> >
>> >
>> > There has also been talk of strapping the 12V feedtrhough for 
>> high power things like a PA
>> >
>> > 
>> <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2010-July/012616.html>http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2010-July/012616.html
>> >
>> > and some suggestion of shorting the 5V fuse and relying on the 
>> regulator to protect itself +/- modifying R6 the series resistor
>> >
>> > 
>> <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2010-July/012617.html>http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2010-July/012617.html
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