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PICList Thread
'[PIC]:something unusual'
2001\01\23@022058 by Nuri ERGINER

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face
Hi,

I program and build my first pic16f84a project it is offcourse a flashing
led.
What is unusual is the circuit is working when I touched the 4 mhz cristal
by my hand.
I connect 3 470 resistor to rb0,rb1,rb2 then I connect 3 led between
resistors and ground.
I use 4mhz cristal connected to pic and I use 2 22pf cristal to ground I
connect the vss and vdd.

Is there any mistake with the circuit?

Regards,
Nuri Erginer

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2001\01\23@025523 by Jinx

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How far from the PIC is the crystal ?

No dry joints (you might be pushing the crystal slightly) ?

Solder a wire between the crystal case and ground - careful
not to heat the case too much, be quick

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2001\01\23@034818 by Ian Rozowsky

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Try a small (+-270R) resistor in series with the crystal.

Ian Rozowsky
Engineering Manager
Centurion Systems
P.O. Box 506
Cramerview 2060
South Africa
Tel   : +27-11-462-4499
Fax   : +27-11-704-3412
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{Original Message removed}

2001\01\23@042404 by JP.BROWN

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Nuri did you remember to take MCLR (pin 4) through a resistor to Vcc?

On Tue, 23 Jan 2001, Nuri ERGINER wrote:

{Quote hidden}

         -----  John P. Brown      .....J.P.BrownKILLspamspam@spam@bradford.ac.uk ----
          \            --- Witty remark goes here ---         /
           --------------------------------------------------

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2001\01\23@044125 by Francois Robbertze

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I had this problem once...

Check if your 16f84 is not set up for any thing else than XT ossilator.
(Mine was set for th RC ossilator and did the same...)

{Original Message removed}

2001\01\23@093124 by Olin Lathrop

face picon face
> I program and build my first pic16f84a project it is offcourse a flashing
> led.
> What is unusual is the circuit is working when I touched the 4 mhz cristal
> by my hand.

It's not unusual at all.  Well designed crystal circuits shouldn't be
that sensitive to someone touching the crystal can, especially at the
relatively low frequency of 4MHz.

> I connect 3 470 resistor to rb0,rb1,rb2 then I connect 3 led between
> resistors and ground.
> I use 4mhz cristal connected to pic and I use 2 22pf cristal to ground I
> connect the vss and vdd.
>
> Is there any mistake with the circuit?

You haven't described any problem with its operation, so apparently not.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olinspamKILLspamembedinc.com, http://www.embedinc.com

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2001\01\23@141648 by uter van ooijen & floortje hanneman

picon face
> I connect 3 470 resistor to rb0,rb1,rb2 then I connect 3 led between
> resistors and ground.
> I use 4mhz cristal connected to pic and I use 2 22pf cristal to ground I
> connect the vss and vdd.

MCLR?
vss/vdd decoupling?

Wouter

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2001\01\23@164518 by Tony Nixon

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Nuri ERGINER wrote:
>
> Hi,
>
> I program and build my first pic16f84a project it is offcourse a flashing
> led.
> What is unusual is the circuit is working when I touched the 4 mhz cristal
> by my hand.
> I connect 3 470 resistor to rb0,rb1,rb2 then I connect 3 led between
> resistors and ground.
> I use 4mhz cristal connected to pic and I use 2 22pf cristal to ground I
> connect the vss and vdd.
>
> Is there any mistake with the circuit?
>
> Regards,
> Nuri Erginer


Have you set all the unused I/O pins as outputs to stop them floating?

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Best regards

Tony

mICro's
http://www.picnpoke.com
.....salesKILLspamspam.....picnpoke.com

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2001\01\24@015004 by dr. Imre Bartfai

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Hi,

your description is somewhat strange. Could you exactly describe how the
condensators are connected to? (Vdd is suspicious...)

Regards,
Imre


On Tue, 23 Jan 2001, Nuri ERGINER wrote:

{Quote hidden}

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2001\01\24@015845 by Nuri ERGINER

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Thanks alot for your helps I found what is wron. I choose rc instate of XT
while programming the pic

{Original Message removed}

2001\01\24@213206 by Dan Devine

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Hi Nuri,

maybe this has already been answered, but I had the same problem on my
first project.

In fact, I had the it on the second too......

In my case, the crystal type (specified in the fuses) was incorrect for
the actual type of unit I was using (i.e. HS, XT, RC).

Soon as I figured it out, it worked great


Dan D

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'[PIC]:something unusual'
2001\02\21@234902 by Aart
picon face
Hi,

i think you left MCLR (pin4 at the 16F84) open. Try putting it at 5V with an
65KOhm resistor between it.

Aart.
{Original Message removed}

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