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'Beginners Problem ??'
1999\03\10@234738 by Sean Breheny

face picon face
Hi,

Off hand,I would ask three questions:

#1) What is your power supply to the PIC?
#2) How exactly do you produce that square wave from the AC supply? In
other words,what is between the AC line and the PIC?
#3) What value are those resistors going to the LEDs?

I'm thinking that there are several possibile causes of your problem,which
include:

#1) A power supply which is erratic, inadequate for the power consumption,
not-decoupled (inadequate cap on the PIC's Vdd pin),doesn't rise
monotonically and quickly on power-up,or a combination of these.

#2) The circuit which transfers the square wave to the PIC pin could be
allowing high voltage pulses to reach the PIC pin,thereby conducting
through the input-protection diodes and raising the Vdd supply line
periodically,thus making the power supply to the PIC unsuitable.

#3) The total power drain of the LEDs exceedes the max total source or sink
current of PORTB (100mA source,150mA sink),therefore causing the PIC to
lock up if the number of lit LEDs is greater than a certain number.

Sean

At 09:59 AM 3/11/99 +0530, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
spam_OUTshb7TakeThisOuTspamcornell.edu ICQ #: 3329174

1999\03\11@100014 by jamesp

picon face
Biswanath,

The first things I would check are the power supply to make sure
it is at the correct voltage and is stable, Put a 10K pullup on
RESET, and I would put the input on RA4 as opposed to RA1, because it is a schmi
tt
trigger input, and will square up the incoming pulses. RA4 would also need a
10K pullup as it is OPEN
DRAIN.   And, I would add 10 uF and .01 uF caps to Vdd for
bypassing if you don't already have them there.  When I design
something new whether for me or someone else, I try to use my
general rules of overengineering to get the design working and
stable.  Then I start taking away parts to find out which are
absolutely necessary, and which can be done without.  This
method hasn't let me down yet.  I'd be interested to know if
these suggestions have any impact whether positive or negative.

                                      Regards,

                                        Jim





{Quote hidden}

1999\03\11@190540 by Sean Breheny

face picon face
Hi Jim,

You are making very good points but there is just one thing: RA4 doesn't
need a pull-up when it is being used as an input. The pull-up only applies
to it when it is acting as an output,that is when it has an open drain
configuration.

Sean

At 08:54 AM 3/11/99 -600, you wrote:
>Biswanath,
>
>The first things I would check are the power supply to make sure
>it is at the correct voltage and is stable, Put a 10K pullup on
>RESET, and I would put the input on RA4 as opposed to RA1, because it is a
schmitt
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
.....shb7KILLspamspam@spam@cornell.edu ICQ #: 3329174

1999\03\11@220542 by Biswanath Dutta

flavicon
picon face
Thanks Sean --  Answer to your questions --

1) I'm using a prototyping kit which has a rectifier, 1000mfd, 5V regulator --
and is supposed to take in AC. It has a jack which just fitted a small AC
adapter which I happened to have -- it produces 12V DC, no regulation -- so I
just plugged that in. Getting about 4.95V

There may be a problem here -- with the power supply rise time as you have
mentioned.
How important is this & why ?

2) I'm using a 2N2222A transistor -- emittor to gnd, 22K to base, 5.6K
collector to +5V, collector to Pic input. AC voltage is isolated from the mains
by a trafo which gives 22V, connected between 22K and gnd.

3)  470 ohms in series with each LED.

Hope this helps to understand the problem.

Thanks to Mr. & Mrs Paul also for responding.

Biswanath Dutta

Sean Breheny wrote:

{Quote hidden}

1999\03\12@191159 by Sean Breheny

face picon face
Hi again Biswanath,

At 08:22 AM 3/12/99 +0530, you wrote:
>Thanks Sean --  Answer to your questions --

You are very welcome. I just hope we can solve your problem. I know someone
here can.

>
>1) I'm using a prototyping kit which has a rectifier, 1000mfd, 5V
regulator --
>and is supposed to take in AC. It has a jack which just fitted a small AC
>adapter which I happened to have -- it produces 12V DC, no regulation -- so I
>just plugged that in. Getting about 4.95V
>
>There may be a problem here -- with the power supply rise time as you have
>mentioned.
>How important is this & why ?

No,it sounds as if your supply is pretty good. I'd just try adding a 10uF
or so electrolytic cap and a 0.1uF ceramic cap directly between the PIC's
Vdd and Vss pins. I think your supply should rise quickly and monotonically
as it is. The problem with the supply not rising quickly and monotonically
is this: when a PIC first receives power,it holds itself in reset for a
short period of time (if the Power up start timer is enabled). If the power
is not up to its full value by then,the PIC can begin running code in an
unreliable manner or lock up. If the power doesn't rise steadily (i.e. it
dips) during power up,then the PIC can enter a metastable state (it locks
up and won't run code until the power is removed and re-applied). I must
admit that I don't know the particular mechanisms by which this happens in
a PIC,but I think the basic idea is that a PIC is a large sequential logic
circuit. In order to work properly, certain registers (such as the PC) must
get set to their startup values. If the power is not good enough,the
mechanisms which are supposed to set these registers may not set them,or
the registers may lose their contents after being set.

>
>2) I'm using a 2N2222A transistor -- emittor to gnd, 22K to base, 5.6K
>collector to +5V, collector to Pic input. AC voltage is isolated from the
mains
>by a trafo which gives 22V, connected between 22K and gnd.

This could possibly be the problem,although I can't offhand see why it
shouldn't work O.K.. You should be able to do what you want by simply
putting about a 220K resistor between the PIC pin and the output of the
transformer. This will allow the PIC's protection diodes to clip the
voltage with very minimal current flow.

>
>3)  470 ohms in series with each LED.
>

This sounds O.K,it would yield somewhere around 50mA max,less than the rating.

>Hope this helps to understand the problem.
>
>Thanks to Mr. & Mrs Paul also for responding.
>
>Biswanath Dutta
>

Try what was suggested above and let us know what happens.

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
.....shb7KILLspamspam.....cornell.edu ICQ #: 3329174

1999\03\12@211232 by Biswanath Dutta

flavicon
picon face
Hi Sean,

Thanks once again.

I went back to the dtasheets and saw the PWRT problem mentioned by you.
BTW, I also have external reset Circuitry connected to MCLR -- 10K to VDD, 10mfd
to gnd.
Re: Power-up timer.  Logically, shouldn't the timer start timing after proper
voltage is reached ? ie. 2 V or more ? Why do they have it this way ? Any idea ?
At what voltage does the timer start ?
Shall try a few changes with the power supply and line input, and get back to yo
u.

Regards  -- Biswanath Dutta


Sean Breheny wrote:

{Quote hidden}

1999\03\12@214956 by Jim Paul

picon face
Biswanath,

Isn't 10uF a little large for reset?  I would use something about 1 uF or
less.
This would speed up the edges if it was smaller.  Just curious wht you went
with 10 uF?   Also, I intended to mention the power up timer  when I spoke
to
you last time, but it slipped my mind.


Regards,


Jim
{Original Message removed}

1999\03\12@231502 by Wagner Lipnharski

picon face
Hi Biswanath,

I don't want to be a pest in your life, but by the fact
that you are learning, you would understand if I correct
you in few things, and I am sure some other people
around will learn it too.

In electronics there are few standards, and it help us
to communicate universaly with almost no problems.

If you learn this now, you will never forget and will
start with the right foot.

all thousands references are lower case, as;

milli (m) 0.001
micro (µ) 0.000,001
nano  (n) 0.000,000,001
pico  (p) 0.000,000,000,001
deca  (d) 10
centi (c) 100
kilo  (k) 1,000
Mega  (M) 1,000,000 (upper case because the -m- milli)
Giga  (G) 1,000,000,000 (upper case because -g- gram)
...others

Ohms,      or R  Resistance
Farads,    or F  Capacitance
Henris,    or H  Inductance
Volts,     or V    
Current,   or I, or Ampere(s)
Impedance, or Z
Hertz,     or Hz

For example, milli is just "m" it is not an abreviation
form, so it does not carry the dot "m."
Start using the right denomination as much as possible
and quickly you will do it without any effort.

10kOhms, or R10k, not 10K, someone can confuse it with
10 Kelvin degrees.

10uF, not 10mfd, someone can mixup it with milliFarads
or some bad name.

Meter (m) doesn't make confusion with milli (m) since
milli alone doesn't exist. It is quantifying some other
unit, as Volts, grams, even meters (mV, mg, mm).

It is incorrect use the letter "u" for micro, but as
it doesn't make any confusion with anything else, and
as the symbol "µ" is not available directly at the
keyboard, we understand and don't care... grrrr!

I already saw many ways to represent the SI standards,
and everytime I see it wrong, my soul get iced.  
Terrors of the standards:
"mts." for "meters", instead the simple "m",
"hrs." for "hours", "mints." for minutes,  
"K" for "kilo", worse, KG for "kilogram",
looks like "a Kelvin degree in free falling
acceleration at G (gravity) 10m^2/s .

Degrees use the "¡" symbol, as ¡F or ¡C, to type it
just press and hold ALT+SHIFT and type 0 1 7 6 at the
numeric keypad.

The same for "µ" ALT+SHIFT+0181 (not 181)
            "¸" ALT+SHIFT+0189
            "¹" ALT+SHIFT+0188
            "²" ALT+SHIFT+0190

So, make my soul warm... :)

I am sorry, I was born in Brazil, and we use metric
system there, so don't ask me why here in US we use
"lb" and say "pounds"...  or at price lists we use
to write "$150/mil" to represent $150 per thousand...
(I understand because in Portuguese that's perfect,
mil = thousand).
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\13@032641 by Gerhard Fiedler

picon face
At 23:12 03/12/99 -0500, Wagner Lipnharski wrote:
>I don't want to be a pest in your life,
...
>you would understand if I correct you in few things,

i had to repeat the above :)

> milli (m) 0.001
> centi (c) 100
> kilo  (k) 1,000

as a matter of fact, centi is 0.01 (not 100) as in cm (centimeter):
100cm=1m, but i'm not sure whether centi is actually part of the SI. "cm"
is probably the only really common use for "c".

> Ohms,      or R  Resistance
> Farads,    or F  Capacitance
> Henris,    or H  Inductance
> Volts,     or V    
> Current,   or I, or Ampere(s)
> Impedance, or Z
> Hertz,     or Hz

here the common abbreviations for the different -- how's that called? here
i am right at the edge of my language skills -- you-know-what-i-mean :) and
their units got mixed up (what exactly i mean will be clearer from the
slightly modified list):

capacitance (C) in Farad (F); common pF, nF, µF (uF), mF
inductance (L) in Henry (H); common µH (uH), mH
voltage (V) in Volt (V), common mV, V, kV
current (I) in Ampre (A); common pA, nA, µA (uA), mA, A
resistance (R) in Ohm (greek Omega; often R, because Omega is rare in fonts
and on keyboards); common mOhm, Ohm, kOhm, MOhm
impedance (Z) in Ohm, too
power (P) in Watt (W); common µW (uW), mW, W, kW, MW, GW, TW
frequency (f) in Hertz (Hz = 1/s); common Hz, kHz, MHz, GHz

here one starts to see the beauty of the SI: =all= units  are
multiplications/divisions of the 7 base units meter [m], second [s],
kilogram [kg], Ampre [A], Kelvin [K], mol (how's that in english?),
candela [cd].

for example (units in brackets):
time (t) is   [s]
length (l) is   [m]
speed (v) is l/t   [m/s]
acceleration (a) is v/t   [m/s^2]
mass (m) is   [kg]
force (F) is m*a   [kg*m/s^2 = N (Newton)]
work (W) is F*l   [kg*m^2/s^2 = Nm (Newton-meter)= J (Joules) = Ws
(Watt-second)]
power (P) is W/t   [kg*m^2/s^3 = Nm/s = W (Watt)]
current (I) is   [A]
voltage (v) is P/I   [kg*m^2/(s^3*A) = V (Volt)]
resistance is v/I   [kg*m^2/(s^3*A^2) = Ohm]
capacitance is I*t/v   [s^4*A^2/(kg*m^2) = As/V = F (Farad)]

... and so on. i think this is pretty nice, especially since you can get to
one unit from different directions (like from mechanical relations and from
electrical relations), and it always works out right -- and with the units
getting "transparent," you see that all of them actually are related. you
would think "how's pounds and gallons related to Ohm?" -- but they actually
are. resistance relates to voltage and current, these relate to power,
which relates to work, which relates to length and force, which relate to
volume (gallons) and mass (pound), respectively. only that gallon and pound
don't give Ohm.

basically this is why i like the SI (also called the "metric system"). (the
only inconsistency is that "kg" as a base unit already has a multiplicator
with it. but one can live with that... :)  


>Meter (m) doesn't make confusion with milli (m) since
>milli alone doesn't exist. It is quantifying some other
>unit, as Volts, grams, even meters (mV, mg, mm).

and to make things clear the upper and lower case =is= significant. not
always, often it is actually redundant if the context is clear, but you
never know... somebody else might think in a different context.

>It is incorrect use the letter "u" for micro, but as
>it doesn't make any confusion with anything else, and
>as the symbol "µ" is not available directly at the
>keyboard, we understand and don't care... grrrr!

i mostly use (windows) "US International" which has a lot of the nifty
characters (including all the portuguese accents and tildes :) and switches
easily back and forth between it and the normal US keyboard (eg. for
programming).

>Degrees use the "¡" symbol, as ¡F or ¡C, to type it
>just press and hold ALT+SHIFT and type 0 1 7 6 at the
>numeric keypad.

if you type it on the numeric keypad, you don't need the shift (only the
alt key) -- at least with num lock on and on my keyboard.

on the US International ¡ is <right-alt><shift>;

>The same for "µ" ALT+SHIFT+0181 (not 181)  => is <right-alt>m
>             "¸" ALT+SHIFT+0189 => is <right-alt>7
>             "¹" ALT+SHIFT+0188 => is <right-alt>6
>             "²" ALT+SHIFT+0190 => is <right-alt>8

but there might be a problem with these characters. they are not standard
(7bit) ascii, so some non-windows recipients may actually see garbage here.
is that a problem or are such characters within the accepted use policy? :)

ge

1999\03\13@082624 by Bob Drzyzgula

flavicon
face
On Sat, Mar 13, 1999 at 12:24:06AM -0800, Gerhard Fiedler wrote:
> At 23:12 03/12/99 -0500, Wagner Lipnharski wrote:
> >I don't want to be a pest in your life,
> ...
> >you would understand if I correct you in few things,
>
> here the common abbreviations for the different -- how's that called? here
> i am right at the edge of my language skills -- you-know-what-i-mean :) and
> their units got mixed up (what exactly i mean will be clearer from the
> slightly modified list):

Here is some word usage that may help you write what you wanted to say:

Electrical current intensity is one of the basic quantities covered
by International System of Units (SI). The symbol for electrical
current intensity is I. The SI unit for electrical current intensity
is the ampre, which is given the symbol A.

> here one starts to see the beauty of the SI: =all= units  are
> multiplications/divisions of the 7 base units meter [m], second [s],
> kilogram [kg], Ampre [A], Kelvin [K], mol (how's that in english?),
> candela [cd].

In english, "mole" is the name of the basic quantity, while
"mol" is the symbol for the unit.

> ... and so on. i think this is pretty nice

No argument here. Now if I could just remember how many
teaspoons in a tablespoon, and how many tablespoons in
a cup...

> They are not standard
> (7bit) ascii, so some non-windows recipients may actually see garbage here.
> is that a problem or are such characters within the accepted use policy? :)

I had this concern as well. For what it is worth, the
"vim" editor under a stock RedHat Linux system displays
the symbols just fine, as does the "mutt" mail reader.
But I know that there are many editors and browsers
that are not so functional as these.

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
bobspamspam_OUTdrzyzgula.org                until something bad happens
============================================================

1999\03\13@093156 by Marc

flavicon
face
> as a matter of fact, centi is 0.01 (not 100) as in cm (centimeter):
> 100cm=1m, but i'm not sure whether centi is actually part of the SI. "cm"
> is probably the only really common use for "c".

"cl" is, too (0.01 liters).

1999\03\13@094616 by Bob Drzyzgula

flavicon
face
On Sat, Mar 13, 1999 at 03:11:52PM +0100, Marc wrote:
> > as a matter of fact, centi is 0.01 (not 100) as in cm (centimeter):
> > 100cm=1m, but i'm not sure whether centi is actually part of the SI. "cm"
> > is probably the only really common use for "c".
>
> "cl" is, too (0.01 liters).

And "cg", centigram, is found on high-precision lab scales.

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
@spam@bobKILLspamspamdrzyzgula.org                until something bad happens
============================================================

1999\03\13@101841 by Nick Taylor

picon face
How many is "one billion"?
Is it 1,000,000 or 1,000,000,000?

- - - Nick - - -

1999\03\13@102638 by ryan pogge

flavicon
face
1,000,000,000  is one billion
1,000,000          is one million



>How many is "one billion"?
>Is it 1,000,000 or 1,000,000,000?
>
> - - - Nick - - -
>

1999\03\13@102850 by Dave VanHorn

flavicon
face
>How many is "one billion"?
>Is it 1,000,000 or 1,000,000,000?
>
> - - - Nick - - -


it's not 1,000,000  but the rest depends on  where you are.

1999\03\13@104751 by Nick Taylor

picon face
I lost count of my zeroes ...
is "one billion" equal to
one thousand millions or
one million millions?

- - - Nick - - -

1999\03\13@105402 by Harold Hallikainen

picon face
One billion is a thousand million in the US and a million million in the
UK.

Harold


On Sat, 13 Mar 1999 07:47:07 -0800 Nick Taylor <KILLspamntaylorKILLspamspamINAME.COM>
writes:
>I lost count of my zeroes ...
>is "one billion" equal to
>one thousand millions or
>one million millions?
>
>- - - Nick - - -
>

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1999\03\13@114926 by Wagner Lipnharski

picon face
Gerhard Fiedler wrote:
> >Degrees use the "¡" symbol, as ¡F or ¡C, to type it
> >just press and hold ALT+SHIFT and type 0 1 7 6 at the
> >numeric keypad.
>
> if you type it on the numeric keypad, you don't need the shift (only the
> alt key) -- at least with num lock on and on my keyboard.

In pure DOS using any text editor, you don't need to hold down
shift, but in some windows editors, if not at all, it makes
a difference since windows interpret it as ALT+PgDn when
pressing ALT+3 at the numeric keyboard. This is why you need
to select "numeric" state with [shift] or [numeric lock].

> basically this is why i like the SI (also called the "metric
> system")....
Not trying to create any problem here, please, but comparing,
a meter/1000 is just "mm", how in standard form you represent
a inch/10? 3/32 + 3/512 + 3/8192 + 3/65536 + 3/1048576 + ... ?  

est‡ certo Gerhard?
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\13@122446 by Wagner Lipnharski

picon face
Harold Hallikainen wrote:
>
> One billion is a thousand million in the US and a million million in the
> UK.
>
> Harold


So, you mean that all over the world, is this:

(1) Million        10^6
(2) Billion (bi)   10^9
(3) Trillion (tri) 10^12
(4) QuaWhat? Quallion? hehe

and in United Kingdom is:

(1)   Million           10^6
(1.5) Thousand Millions 10^9
(2)   Billion           10^12
(2.5) Thousand Billions 10^15
(3)   Trillion          10^18
and so on?

I need to take care when writing my checks to you guys
in UK... about the billions I mean.

Somebody said that it is easy not to see the dot "."
in the middle of a resistor value, as 4.7k Ohms, instead
the common use of 4k7, probably this is why in portuguese
we use "comma" instead the "dot", for the decimal reference,
as 4,7k Ohms, or 2,5cm. Yes, our thousand separators is
the... "dot".  2.512,25 means two thousand, five hundred...
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\13@123522 by Sean Breheny

face picon face
At 12:22 PM 3/13/99 -0500, you wrote:
>the common use of 4k7, probably this is why in portuguese
>we use "comma" instead the "dot", for the decimal reference,
>as 4,7k Ohms, or 2,5cm. Yes, our thousand separators is
>the... "dot".  2.512,25 means two thousand, five hundred...

You probably know this,but that isn't just in Portuguese,but in
Spanish,French,and I think several other European languages.

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
RemoveMEshb7TakeThisOuTspamcornell.edu ICQ #: 3329174

1999\03\13@132821 by rweaver8

flavicon
face
Thank you for your run down on basic electrical terms. I am pretty much
familure with them. Dont think your rundown was wasted though. I did
learn something from it: How to type degrees. I have always wondered how
to do that.
Ralph

1999\03\13@140222 by Gerhard Fiedler

picon face
At 12:22 03/13/99 -0500, Wagner Lipnharski wrote:
>So, you mean that all over the world, is this:
>
>(1) Million        10^6
>(2) Billion (bi)   10^9

actually, in germany a "Billion" is 10^12, too, not only in the uk. 10^9
would be a "Milliarde". you better make your clients use plain numbers
(without decimal points/commas and without commas/points to separate the
thousands) for you BIG checks... :)

ge

1999\03\13@140224 by Gerhard Fiedler

picon face
At 11:48 03/13/99 -0500, Wagner Lipnharski wrote:
>Not trying to create any problem here, please, but comparing,
>a meter/1000 is just "mm", how in standard form you represent
>a inch/10? 3/32 + 3/512 + 3/8192 + 3/65536 + 3/1048576 + ... ?

well, in electronics we got used to call "inch/10" "100mil" :)  =somebody=
on this side of the ocean must have had a need to facilitate calculations
and start counting in decimals rather than in binary fractions...

ge

1999\03\13@140226 by Bertel Schmitt

picon face
Depends on where you are. In Germany (for instance), a billion equals a
million millions, whereas in the USA, it equals a thousand millions. Makes
takeover talks between European and US companies very interesting ....

BS


At 04:47 PM 3/13/99 , Nick wrote:
>I lost count of my zeroes ...
>is "one billion" equal to
>one thousand millions or
>one million millions?

1999\03\13@141047 by Gerhard Fiedler

picon face
At 08:25 03/13/99 -0500, Bob Drzyzgula wrote:
>Here is some word usage that may help you write what you wanted to say:
>
>Electrical current intensity is one of the basic quantities ...

thanks. "quantity" was the word i couldn't come up with. i'll get better...
patience. :)

ge

1999\03\13@144831 by Wagner Lipnharski

picon face
just a silly thing for laughing:

if Volts = Resistance × Current,
what is the voltage in a charged perfect capacitor,
where the resistance between the plates is infinite,
with zero current flowing between them?
... hmmm, how much is Infinite × Zero?

so, the charged electrons matter in this capacitor?

Can we say a capacitor does not hold "Voltage", but
"charged potential capacity to creates current"?


Another:

If Resistance is  Voltage / Current,
a simple wire connected to nothing, flowing zero
Amperes, will has zero volts on its ends. So, what
is its resistance?

Zero / Zero = Zero?  It can be an isolant!!! and
will has a zero resitance in this situation???
--------------------------------------------------------
Wagner Lipnharski

1999\03\13@162133 by Gerhard Fiedler

picon face
At 14:46 03/13/99 -0500, Wagner Lipnharski wrote:
>just a silly thing for laughing:

maybe, but in case you take it seriously, they do have answers...

>if Volts = Resistance Current,
>what is the voltage in a charged perfect capacitor,
>where the resistance between the plates is infinite,
>with zero current flowing between them?
>... hmmm, how much is Infinite Zero?

1) this formula of course applies only where there is =only= resistance
involved (ie. other contributors like capacity negligible). in an ideal
capacitor, the formula is

v = Q / C

(why would you apply the formula for an ideal =resistor= to an ideal
=capacitor=? don't confuse people here... somebody might take you seriously :)

2) "infinite" is not a number and neither a reality. what you actually do
have is a very high value for the resistance and a very low value for the
current. (how long do =your= capacitors hold a charge? mine discharge in
times a whole lot smaller than "infinity." :)

>so, the charged electrons matter in this capacitor?

of course, that's Q [As], the charge in the cap.

>Can we say a capacitor does not hold "Voltage", but
>"charged potential capacity to creates current"?

that's exactly what "voltage" is, i guess.


>If Resistance is  Voltage / Current,
>a simple wire connected to nothing, flowing zero
>Amperes, will has zero volts on its ends. So, what
>is its resistance?
>
>Zero / Zero = Zero?  It can be an isolant!!! and
>will has a zero resitance in this situation???

as long as there is no voltage and no current, the resistance is not
defined (and neither known). this follows from both the mathematical
approach (division through 0 is not defined) and the physical approach
(resistance =is= defined as the relationship between the voltage and the
current, and without any of them there is no way to determine the resistance).

we often talk about resistance (and other quantities of parts) in a pretty
abstract way, without being aware of it. for example, when you say "this
resistor has 5k1," what you actually mean is "when i send a dc current of 1
mA through this resistor, i can measure a voltage of 5V1 at its terminals."
which doesn't necessarily mean that the equivalent is true for 1fA or 1kA.
in these cases, the resistance of the same part might well be a whole lot
different, because it creates a different voltage than the one derived from
the resistance at 1mA. so the resistance of our "5k1 resistor part" at 0 A
is actually not only not defined but also not known. and in some real cases
this fact that the values are only valid over a certain range may create
problems -- always then when you get out of the linear range of your parts
(eg. over voltage for resistors or high frequencies for caps, to cite two
common cases).

ge

1999\03\13@205128 by rweaver8

flavicon
face
The easy way to remember is a billion is a thousand million.

Ralph

Nick Taylor wrote:
>
> How many is "one billion"?
> Is it 1,000,000 or 1,000,000,000?
>
>  - - - Nick - - -

1999\03\14@071356 by g.daniel.invent.design

flavicon
face
Wagner Lipnharski wrote:
> So, you mean that all over the world, is this:
> (2) Billion  10^9

> and in United Kingdom is:
> (2) Billion  10^12

Not just the U.K. Wagner, somehow the newer Americans lost three zeros
during their settlement of America in their race to become:
               Yankee "Bilionaires"

Regards,
Graham Daniel (N.Z.)

1999\03\14@223448 by Biswanath Dutta

flavicon
picon face
Hi Everybody.

Wow ! This is what the list is all about. I am amazed with the time &
effort you obviously very busy people spend in answering to the postings
on the list. Just going through them can be quite enlightening. Thanks
to all. Hope to be able to contribute my wee bit sometime in future.

Wagner --   Not a pest at all. As you rightly said, we are all perpetual
learners and I not any less than anybody else. I find learning very
exciting and that's what makes this ever changing field of electronics &
microcontrollers so interesting. You are most welcome.

Sean --      I added the caps to the IC pins as suggested by you --
didn't help much to improve the situation but I've kept them on any way
since its a good idea.
I am getting convinced that the problem may be due to stray capacitances
and noise pickups -- due to the following reasons--

1) The behaviour has changed somewhat (with or without the above caps) .
Now it locks up less often. Even when it does (happens only during
power-up), external reset gets it working.
2) I've got another beginner's program working, and its working fine --
two 7 seg. LED displays displaying 00 to 99 on command from UP/DN
buttons. No power up problems.

Specially due to point 1 above I shall rewire the circuit and let you
know.

Thanks --  Biswanath

1999\03\14@234122 by AJAY WAZIR
flavicon
picon face
part 0 1513 bytes

-----Original Message-----
From:   Biswanath Dutta [SMTP:spamBeGonesavlinkspamBeGonespamCAL.VSNL.NET.IN]
Sent:   Monday, March 15, 1999 7:37 AM
To:     TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
Subject:        Re: Beginners Problem ??

Hi Everybody.

Wow ! This is what the list is all about. I am amazed with the time &
effort you obviously very busy people spend in answering to the postings
on the list. Just going through them can be quite enlightening. Thanks
to all. Hope to be able to contribute my wee bit sometime in future.

Wagner --   Not a pest at all. As you rightly said, we are all perpetual
learners and I not any less than anybody else. I find learning very
exciting and that's what makes this ever changing field of electronics &
microcontrollers so interesting. You are most welcome.

Sean --      I added the caps to the IC pins as suggested by you --
didn't help much to improve the situation but I've kept them on any way
since its a good idea.
I am getting convinced that the problem may be due to stray capacitances
and noise pickups -- due to the following reasons--

1) The behaviour has changed somewhat (with or without the above caps) .
Now it locks up less often. Even when it does (happens only during
power-up), external reset gets it working.
2) I've got another beginner's program working, and its working fine --
two 7 seg. LED displays displaying 00 to 99 on command from UP/DN
buttons. No power up problems.

Specially due to point 1 above I shall rewire the circuit and let you
know.

Thanks --  Biswanath

1999\03\16@041855 by Dr. Imre Bartfai

flavicon
face
Hi,

I think the phrase "all over the world" is not precise. For instance, here
in Hungary, a billion is also 10^12. The number 10^9 is called here
"milliard" (I do not know whether this is general). 10^24 is quadrillion,
10^30 is quintillion, etc. In Hungary, in 1946 there was the hugest money
inflation of the world, so there existed such money note as xxx
quadrillion...

Imre


On Sat, 13 Mar 1999, Wagner Lipnharski wrote:

{Quote hidden}

1999\03\18@192200 by Sean Breheny

face picon face
Hi Biswanath,

I'm very sorry for the long delay. I have been very busy and it is hard to
keep track of all my email...

I don't really know about the power-up timer question,I guess part of the
answer is that the chip is designed to work with voltages which are
somewhat lower than 5V so it can't wait until 5V is reached because the
supply might not be that high. That being said, why they couldn't set it to
some voltage above which the chip is guaranteed to work,I don't know.

A couple more suggestions: Try just tieing MCLR to high and eliminating the
reset circuit.

Also,try feeding the circuit pulses from a known good pulse generator and
temporarily disconnecting it from the mains. I still sorta suspect the
connection to the mains.

Sean


At 07:29 AM 3/13/99 +0530, you wrote:
>Hi Sean,
>
>Thanks once again.
>
>I went back to the dtasheets and saw the PWRT problem mentioned by you.
>BTW, I also have external reset Circuitry connected to MCLR -- 10K to VDD,
10mfd
>to gnd.
>Re: Power-up timer.  Logically, shouldn't the timer start timing after proper
>voltage is reached ? ie. 2 V or more ? Why do they have it this way ? Any
idea ?
>At what voltage does the timer start ?
>Shall try a few changes with the power supply and line input, and get back
to you.
{Quote hidden}

-- so I
{Quote hidden}

rating.
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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