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'[PIC]: IR remote control with a PIC,wake-on-rb-cha'
2002\08\04@180140 by Jinx

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part 1 1081 bytes content-type:text/plain; (decoded 7bit)

> When sleeping, the PIC16F628@4MHz consumes about
> 42uA @ 5V. If I suply it with some AA Alkaline batteries, it
> would mean rougly:  2850mAh / 42uA = 67857 hours =
> 2827 days = 7.74 years without use

What are you basing the "2850mAh" figure on ? Alkaline AAs
I've seen have been under 1000mAh, usually 800mAh, which
would give you more likie 2 years than 8

(btw, the frequency of the micro is irrelevant when it's asleep)

I think you could simplify the circuit by eliminating the gates too.
The attached shows two switches. As Aaron says, get the PIC
to hold a port pin high to supply its own Vcc until it's finished
transmitting or learning. After it's powered itself down there will
be NO current consumption at all until the next switch push

I know others have suggested low power PICs but only under
ideal conditions does the SLEEP current approach the book
value, and it's still too high for small batteries. Most remote
controls use fractions of a uA on standby and you won't get
down that far with a micro




part 2 1703 bytes content-type:image/gif; (decode)


part 3 105 bytes
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2002\08\04@201052 by Russell McMahon

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part 1 2716 bytes content-type:text/plain; (decoded 7bit)

> > When sleeping, the PIC16F628@4MHz consumes about
> > 42uA @ 5V. If I suply it with some AA Alkaline batteries, it
> > would mean rougly:  2850mAh / 42uA = 67857 hours =
> > 2827 days = 7.74 years without use
>
> What are you basing the "2850mAh" figure on ? Alkaline AAs
> I've seen have been under 1000mAh, usually 800mAh, which
> would give you more likie 2 years than 8

My somewhat dated tables suggest a figure of around 2300 mAH for Alkaline
AA's. Some modern cells will presumably be at the higher figure Edson used.
Note that actual delivered mAH depends on laod and low laods tend to give a
much higher figure.

> I think you could simplify the circuit by eliminating the gates too.
> The attached shows two switches. As Aaron says, get the PIC
> to hold a port pin high to supply its own Vcc until it's finished
> transmitting or learning. After it's powered itself down there will
> be NO current consumption at all until the next switch push

If I understand this circuit correctly the PIC is holding itself up by its
own bootsraps with no visible means of support - ie powering its own Vcc
from poert pins which draw power from Vcc which .... Quite possibly I am
missing something.

A functionally equivalent arrangement is to use the PIC to turn on a
transistor (bipolar or FET) which provides Vcc while required and turns
itself off by disabling the transistor when finished. The cleanest way is a
high side switch (transistor). The trouble is that this needs a low level to
be on and a high level to turn off  As the PIC pins will usually go to a low
state when off (with a high side switch) the polarity is difficult to
achieve. Adding 1 extra transistor simplifies design although it could
probably be achieved with care with a single transistor.

The attached diagram is party of a real world circuit that works. Power is
turned on by pressing button "Sw" and is held on by PIC as long as required.
Not all the components shown are needed for a simple application but it
shows that there can be more to this than meets the eye. Without going back
into my design I would not be sure why everything was there now. It looks
too complex for what it does but everything there was deemed necessary at
the time. (I can't imagine why the zener is there :-) ). The two PIC pins
used probably relate to the need for the switch to be functional as a
push-button when turned on (input to PIC bo) while the power is held on
using PIC b7. Little touches like the BAT85 to prevent input pin being
pulled to either 5v need remembering when voltages over 5 volts are used.



       Russell McMahon





part 2 5106 bytes content-type:image/gif; (decode)


part 3 105 bytes
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2002\08\04@211856 by rusque (Listas)

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Hello Jinx,

> What are you basing the "2850mAh" figure on ? Alkaline AAs
> I've seen have been under 1000mAh, usually 800mAh, which
> would give you more likie 2 years than 8

   I've seen it on a table on a web page that I can't find anymore...

> (btw, the frequency of the micro is irrelevant when it's asleep)

   Oops, sure. :)

   Best regards,

   Brusque

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2002\08\04@235124 by Herbert Graf

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> > What are you basing the "2850mAh" figure on ? Alkaline AAs
> > I've seen have been under 1000mAh, usually 800mAh, which
> > would give you more likie 2 years than 8
>
>     I've seen it on a table on a web page that I can't find anymore...

       I don't know about alkalines but I do know the AA rechargable batteries I
use are 1600mAh. TTYL

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