Tom=E1s =D3 h=C9ilidhe wrote:>
>
> Mark Rages wrote:
>> Why do you need 5V?  The 16F887 is happy at 3V.  It's important to
>> read the "electrical characteristics" part of the datasheet when
>> you're doing the circuit design.
>
> Will the 887 be happy with two AA batteries in series? As the batteries
> begin to deplete will the voltage drop cause the 887 begin to fail?

As Mark wrote, this information is in the datasheet, and as Mark pointed
out, it's important that you take the time to read and understand it.

No, it's not necessarily easy, but you're trying develop a real product
that you intend to sell.  You have to take what you are doing seriously,
and put in the effort you need to master the areas you need to learn, to
design a successful product.  That's not me being nasty and refusing to
answer simple questions or whatever, or saying it was hard for me so it
should be equally hard for you - I'm simply pointing out that, although
help is available, there are no real shortcuts.  At some point, you have
to understand the data sheets yourself.

In this case, you would see that the '887 can run ok right down to 2V, at
8MHz.  And the battery data would tell you that at 1V output, an alkaline
AA battery is finished anyway.  So the answer is that, by the time the
voltage drop causes the 887 to fail, your batteries will be effectively
drained.

I'd be more worried, if I were you, about whether 3V is enough to drive
your LEDs and the impact as voltage falls on LED brightness.  Personally
I'd use 3 x AA to get more headroom - your device is too small to fit
them, but then you could look at AAAs (lower capacity of course, but one
thing you find in engineering is that there is no such thing as magic -
everything is a trade-off).

But please - read those data sheets.


David Meiklejohn

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