>> Just for clarity let me add that this bridge is on Earth where gravity
>> is 9.81 m s-2    :-P
>>    
>
> Does not matter, I was talking about kg not weight ;-)
>
> Anyway, if that bridge doe snot collapse for 3 nights with 80kg of sandbag
> on top of it, would you use it?
>
> What everyone trying to tell you is that these things are not matter of
> theoretical calculations. As components are physical devices you have to
> know that there are far more things have to take into account than you would
> probably like to calculate with. If an ant will go on that bridge with the
> self resonation of it then it will collapse. Does not matter if it was
> designed for 80kg. If one of the labor just made a slight mistake during the
> building process then it may take only 70kg. If you continuously use that
> bridge for the maximum 80kg then all the bricks and cement and everything
> will be overused and the lifetime of that bridge will be degraded to a very
> short time. Maybe this example is not perfect but I hope it shows that you
> have to thinking in a different way.
>
> Tamas
>
>
>
>
> On Mon, Jul 14, 2008 at 6:44 PM, Tomás Ó hÉilidhe <spam_OUTtoeTakeThisOuTlavabit.com> wrote:
>
>  
>> Tamas Rudnai wrote:
>>    
>>> Tomas, this is well explained in the datasheet, but look at this way:
>>>      
>> Let's
>>    
>>> say you weight exactly 80kg, and you need a bridge over a cliff. The
>>> architect designs a bridge that is rated for 80kg only, and according to
>>>      
>> the
>>    
>>> structure and the used material if 80.1 kg is on the bridge it will be
>>>      
>> more
>>    
>>> than likely to collapse. Would you use that bridge?
>>>
>>>      
>> Just for clarity let me add that this bridge is on Earth where gravity
>> is 9.81 m s-2    :-P
>>
>> So the bridge is rated for 80 kg, and it's more than likely to collapse
>> if you apply 80.1 kg
>>
>> Things that need to be taken into account:
>>
>> 1) Whether failure is a "brick wall drop" or whether it's "linear". For
>> instance, this bridge we're talking about, just like the PIC
>> microcontroller, will have a gradual failure as the current is
>> increased. To compare this to how the bridge works, let's say the bridge
>> starts to flex at about 80.02 kg, and begins to sheer at 80.08 kg.
>>
>> 2) The disposition of the manufacturer that gave you those limits. If
>> the manufacturer is reputable, then the bridge probably won't start to
>> flex until about 790 N.
>>
>> If Microchip says 25 mA is the upper limit then we're probably grand up
>> to about 30 mA or so. On the prototype board for my Connect4, I went
>> straight from a PIC pin to an LED to ground, without a current-limiting
>> resistor. I left the device on overnight for three nights in a row and
>> it didn't fail! For the craic I might cut one of the LED legs out to
>> definitively measure the current flow. Also note that I had 7 LED's on
>> at once, so not only was I flouting the "per pin" rule, I also flouted
>> the "all pins" rule! And it still managed to stay working for 3 nights
>> in a row!
>>