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'[PICLIST] Fw: [PIC]: EE challenge PIC && 12V'
2001\01\11@153131 by GMorbe

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Hi all,

thanks for your comments that far. Most of your suggestions tend more or
less to eitherone of my initial concepts except using a reg with a shutdn
capability which is a third idea.

From the standpoint of a simple clean concept one should probably take the
5V LDO. But each of the three concepts are fairly easy to implement. Because
it needs to be Low Cost i tend to leave the decision to the pocket
calculator.

By taking a cheap reg or even a zener then add up 2 transistors, 3 diodes
and some passives, i think there will be no big difference left compared to
the LDO, but it needs to be calculated more exactly to say. The discrete
approach however relies on standard components only.

Germain

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2001\01\12@064631 by Roman Black

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GMorbe wrote:
>
> Hi all,
>
>  thanks for your comments that far. Most of your suggestions tend more or
> less to eitherone of my initial concepts except using a reg with a shutdn
> capability which is a third idea.

> By taking a cheap reg or even a zener then add up 2 transistors, 3 diodes
> and some passives, i think there will be no big difference left compared to
> the LDO, but it needs to be calculated more exactly to say. The discrete
> approach however relies on standard components only.

1. I think you can do it with one transistor/fet. Maybe on
the -ve leg of the battery with some lateral thinking.

2. Diodes and transistor VERY cheap in large quantities,
especially when you factor in the ability to buy broad
spec of parts of reasonable compatibiity, cheapest
tender, specials that month, etc etc. Much better for
your manufacturer, and safer when supplies are
unpredictable.

3. I would look at running the transmittrer section
straight from the battery in a way that it is normally
off. This means your reg only has to do the pic.
So you can use the tiniest of zeners for the reg.

4. I would definitely choose an option that is
completely open circuit when off. Those 23A 12v
batteries are hard to get and expensive. Very
annoying in remotes that go bad when you haven't
used them for a while. We sell these batteries,
to lots of annoyed people I might add! ;o)
-Roman

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2001\01\12@140307 by Peter L. Peres

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Just before you finish calculating:

You can set the PIC to sleep and wake up to check the keys (or keypress
wakeup), and use a LDO regulator that works all the time. This leads to a
minimum parts solution.

Peter

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