[mythtv-users] HDHomeRun Prime iPad app

jedi jedi at mishnet.org
Sat Aug 20 23:54:01 UTC 2011

On Sat, Aug 20, 2011 at 06:36:15PM +0100, Mike Perkins wrote:
> On 20/08/11 18:16, James Van Vleet wrote:
> > On Fri, Aug 19, 2011 at 5:20 PM, Raymond Wagner<raymond at wagnerrp.com>wrote:
> >
> >>> it makes sense to remove as much unnecessary weight as possible.  No,
> >>> this is just some marketing weenie telling the engineers to use external
> >>> supplies because a slightly smaller unit will be more appealing and sell
> >>> more.
> >>
> >
> > I did a brief stint in the appliance hardware thing and based on
> > that experience I don't believe this is the case.  The real reason I
> > discovered is that it is *much* less expensive and painful from a UL (or
> > other equivalent) standpoint to purchase an already approved UL external
> > power supply and feed low voltage into your device.  Doing this can make
> > both the initial UL cert and the updates as the device changes a snap.
> >
> > Otherwise you are feeding 110-220 volts into your device and UL is MUCH more
> > interested in those.
> >
> > Also there is the whole getting that heat out of our device thing, but in
> > our case taking a lot of the UL headaches out of the system was the big win.
> >
> I'd sooner have the heat generated inside the box where the designed-in fan can 
> correctly dispose of it than have it generated by a lump of plastic sitting on 
> the furniture or on the carpet. (A typical 12v supply for a pico-PSU is a brick, 
> not a wall-wart.) Still, I agree with your reasoning as to why they do such things.

   Chances are that the brick is going to be in a better position to radiate
heat even without a fan. Whereas shoving that extra source of heat and noise
generation in your main enclosure is going to just further complicate an 
already rather difficult problem.

   The brick can also be designed specifically to passively radiate heat
better too.


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