[eagle] Re: Receiver Spec vs. ATP, a few Suggestions and aQuestion or Two

Juan Rivera juan-rivera at sbcglobal.net
Sat Jul 28 16:52:44 PDT 2007

Hi Chuck,

I don't think that existing supply is running at 90% efficiency.  I'll have
to solder it back together to take a few measurements but the manufacturer's
specs don't claim quite that much and this one isn't running properly.  I've
got a bit more data in my symposium presentation and I hope to complete that
in the next few days and get it out.

I found a step-down converter that's designed to supply a maximum of about
100 mA and it runs at 400 kHz with automotive temp range.  If no one else
steps up I'll put out some info on this one.



-----Original Message-----
From: Chuck Green [mailto:greencl at mindspring.com] 
Sent: Saturday, July 28, 2007 3:30 PM
To: juan-rivera at sbcglobal.net
Cc: 'Bdale Garbee'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)';
eagle at amsat.org; 'Samsonoff at Mac. Com'; 'Juan.Rivera (Work)'
Subject: Re: [eagle] Re: Receiver Spec vs. ATP, a few Suggestions and
aQuestion or Two

Hi Juan,

I think the reason you have not seen much regarding the CAN-Do redesign 
is that, as far as I know, no one has stepped up to do the power supply 
redesign.  Until that happens, not much else will happen.

I'm not thrilled with the idea of giving up the switching power supply.  
Remember that the efficiency hit must be multiplied by 10-15, the number 
of CAN-Do's on the satellite. 

The "dead-bug" modification is intended to fly.  Those who were not 
around in the early days have no idea what loose wires have flown 
successfully in the past.  That's not to say we should encourage such 
things, just that it's not as ugly to those of us who have seen much 
worse in the past as you might think.  Because of the IC's mass (very 
small) it is probably very secure just the way you see it.  But we will 
also epoxy a radiation shield to it and then conformal coat the whole 
thing with a heave conformal coating which will make it very difficult 
for anything to move.

I'm ready to start a new design (layout) just as soon as someone gives 
us a new power supply design that is quieter, and hopefully, more 
efficient than the 90% we now have.


Juan Rivera wrote:
> Bdale,
> It would be a trade-off.  I've put out all the information I have and
> everyone knows my opinions.  I think someone else is supposed to be
> into this but I forgot who it is since nothing has been posted.  I'd like
> see some alternative suggestions from the experts on the CAN-Do, the
> enclosure, and the EMI situation in general.
> By the way, do I have a prototype CAN-Do module or was the intent to fly
> this version with the dead-bug step-down converter hanging by three leads
> and a few wires?
> Juan
> -----Original Message-----
> From: Bdale Garbee [mailto:bdale at gag.com] 
> Sent: Saturday, July 28, 2007 2:41 PM
> To: juan-rivera at sbcglobal.net
> Cc: 'John B. Stephensen'; David Smith; Dave Black (Work); Dave Black
> eagle at amsat.org; Samsonoff at Mac. Com; Juan.Rivera (Work)
> Subject: Re: [eagle] Receiver Spec vs. ATP, a few Suggestions and
> or Two
> On Fri, 2007-07-27 at 21:23 -0700, Juan Rivera wrote:
>> I have a few thoughts...  The CAN-Do switching step-down converter is
>> only supplying 11 milliamps.  If we take a slight efficiency hit we
>> could just go to a simple linear regulator and completely eliminate
>> the radiated and conducted EMI emission problem from CAN-do.  That
>> eases the EMI filtering and shielding requirements for every single
>> payload.  That seems like a good trade-off to me.
> Hrm.  What makes you say "a slight efficiency hit"?  
> Doing this on one or two modules that are particularly susceptible to
> noise *may* make sense (and I'm certainly open to considering this as an
> alternative), but we're already on our second power supply design on the
> CAN-Do! because the original switcher, which was more efficient than a
> linear regulator, was deemed too inefficient to fly on P3E by our
> AMSAT-DL friends.
> Bdale
> _______________________________________________
> Via the Eagle mailing list courtesy of AMSAT-NA
> Eagle at amsat.org
> http://amsat.org/mailman/listinfo/eagle

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