[pvrusb2] Weird behavior with my Happauge UB-PVR

[Eric A. Bonney]

Mike Isely wrote:
> On Thu, 20 Mar 2008, Eric A. Bonney wrote:
>   
>> I actually only see the issue of the USB HDs changing where they are 
>> mounted at boot time. After that they are always good and they are 
>> plugged into the same power/surge strip as the PVR. I am guessing that 
>> the PVR may be more sensitive than the HDs. If it is a dirty power 
>> issue any suggestions on how to resolve the issue?
>>
>>     
>
> Well not knowing anything about your USB hard drives, I can't really 
> make any comparison about how sensitive they might be compared to the 
> PVR.  The real sensitivity is probably going to depend on how good the 
> power brick / wall wart is.
>
> One thing people don't immediately realize (and I've said this many 
> times in the past) is that PC power supplies are going to be much more 
> robust than an external power supply for a USB device.  A PC power 
> supply manages hundreds of watts and has considerable internal 
> capacitance which can carry it across momentary power glitches.  I kid 
> you not - I have personally witnessed having the lights blink out in my 
> house for 1/4 - 1/2 second and the PC (no UPS!) sails right through it 
> without a hiccup.  Compare that to a power supply for a USB device - 
> such a device will typically be a tiny little switcher with a very low 
> power rating and not much internal capacitance.  A wall wart is not 
> going to be able to sustain its output voltage when there are "gaps" in 
> the incoming power.  A wall wart also isn't going to have anywhere near 
> the filtering of a PC power supply.
>
> I've seen people get unwelcome surprises due to this.  They think the 
> power in their house is clean - because the PC is fine, and then start 
> scratching their heads when the PVR seems to randomly reboot / reconnect 
> once or twice a day.  Because the PVR is "on its own" as far as power 
> supply is concerned, it can't benefit from all the filtering / capacity 
> of the PC power supply.  (And this is not a fault of the PVR since 
> USB-supplied power is limited to 1/2 amp at 5 volts (2.5 watts) which is 
> not enough to run the PVR.  This is why 3.5" external USB hard drives 
> all have external power while far more power-efficient "laptop" style 
> external USB hard drives frequently / barely can run directly off the 
> USB cable.)
>
> There was a case a while back of a pvrusb2 user seeing these symptoms.  
> He ultimately traced the root cause as being the air conditioner in his 
> house.  Every time it turned on, it glitched the AC power in the house, 
> causing his PVR-USB2 device to reset.  His PC was never affected.
>
> I would start by plugging your PVR into a surge protector.  If the 
> problem is surges or EMI, the the surge protector's filtering should 
> help.  If however the problem is due to actual fraction-of-a-second gaps 
> in the line power, then a surge protector won't help.  In that case you 
> need a UPS.  Heck, just get a nice UPS, plug your PC into that and then 
> plug in your PVR to it while you're at it.  If the problem really is 
> dirty power, then that will definitely solve it.
>
>   -Mike
>
>
>   
Ok well now things are making a little more sense. Let me give you more 
feedback on my setup, as I really didn't think it was related until now. :)

I have an APC backup until that everything is plugged into. This until 
will keep power going for about 30 minutes before it shuts off, I have 
tested it to see how long it will last. So the power strip is plugged 
into the APC and then things are plugged into it and also some items are 
plugged directly into the APC unit.

So I am not really sure how short power lapses would cause this issue, 
since the PVR is getting it's power from the APC unit anyways, or at 
least I think it is. I will need to verify that here shortly.

If it isn't then I can understand why my PVR goes from /dev/video0 to 
/dev/video1 once in a while if it loses power. I'll check on my 
configuration shortly and post back...

Thanks a lot for the help guys.

-Eric