[hpsdr] PicoPSU ATX...-12 volt current concern?

[w3sz at epix.net]

I would be interested to hear the 'common wisdom' on this one.  I had similar concerns regarding the issue of Atlas/Ozy/Janus power consumption and so after combing the archives, I went to the TAPR booth at Dayton and asked which supply was recommended for Atlas/Ozy/Janus.  I was shown the A/O/J triad using a pico-psu unit which I was told was "on sale" at www.minibox.com currently with 12 volt AC/DC adapter.  The only such combo I could find on www.minibox.com was the picoPSU-120 Power Kit so I went home and ordered it.  It is true that the rating on this for -12V is 0.05A.  Peak rating for -12V is 0.1A.   I guess it is possible that there was another, higher power combo on sale at www.minibox.com and that I just missed it and ordered the wrong unit, but I looked carefully for a long time and couldn't find any other such combo deals.  I considered ordering the PW-200-M but decided to go with the unit that appeared to be exactly what was shown to me at the TAPR booth.

I figured that since [I thought] it was being used, demoed, and recommended by some of the TAPR staff that it should work OK. Based on that logic, I ordered one.  It is due to
arrive here Tuesday and I am finishing the Atlas board today so that I am ready for its arrival in 48 hours.  My expectation is that it will work fine as long as I don't expand beyond the A/O/J triad.  When I do expand further, I am prepared to get another supply.

I considered and specifically rejected using a large switching supply because of the fact that the current requirement of the A/O/J combo from its +12V supply was probably a couple of orders of magnitude below the maximum current rating of the +12 V rating of those switching supplies I had available:
http://www.pcpower.com/products/viewproduct.php?show=T51ATX&view=techspecs .    Perhaps this decision was a mistake.  I could have built a linear supply to supply the 'other' voltages, but the pico-psu combo was easy, didn't waste a lot of power, and was cheap.


The URL for the pico-psu which was [I thought] recommended to me at the TAPR booth at Dayton is:
http://www.mini-box.com/picoPSU-120-power-kit?sc=8&category=13

This is referenced from a page with more choices at:
http://www.mini-box.com/s.nl/sc.8/category.13/.f

The manual for the picopsu-120 is at
http://resources.mini-box.com/online/PWR-PICOPSU-120/PWR-PICOPSU-120-manual-engl.pdf

The PW-200-M gives 0.1A [0.2A peak] for -12 V.  It is also referenced on the page:
http://www.mini-box.com/s.nl/sc.8/category.13/.f

and its manual is at:

http://resources.mini-box.com/online/PWR-PW-200-M/PWR-PW-200-M-manual.pdf

It might be that a wiser choice at this point, rather than the picopsu-120, would be to get the PW-200-M.

Thanks in advance for your comments, and

73,

W3SZ
Roger Rehr
http://www.nitehawk.com/w3sz


Quoting Kurt Loken <ae6uj at yahoo.com>:

[Hide Quoted Text]
***** High Performance Software Defined Radio Discussion List *****

Hello Everyone,

So I'm trying to make my first contribution to the FAQ
and I already need some help.  Here is the question
"What is the recommended means of powering the ATLAS?"
Yes, an ATX power supply will work, but...

The PicoPSU ATX is nifty looking unit  (I was ready to
order one myself),  A picture of it plugged into the
Atlas board even graces Page 1 of the the Atlas
assembly documentation on the TAPR website.  But since
it is only rated for 50ma on -12v, do we want make a
warning to people in the FAQ not to buy this
particular unit and to be mindful of the -12V current
requirements for the ATX supplies they do choose?

As a reminder...Bill Tracey reported that with
Ozy/Janus playing radio with an SDR 1000 had a -12V
current draw of 70 ma.  I assume this will only
increase with the future boards plugged into Atlas.

Let me know if I should put a warning in the FAQ
answer for this particular unit.

Regards,

Kurt - ae6uj



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