Searching \ for 'Protecting PICs' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=pic
Search entire site for: 'Protecting PICs'.

Truncated match.
PICList Thread
'Protecting PICs'
1999\03\29@162745 by Holger Morgen

flavicon
face
Hi -

I'm building a cable tester for 8 wire UTP, cat III - V (normal 10Mb/s
network cables) up to 100m.
Using a 16F84 I am wondering if I should use any ESD prevention.

My setup looks something like this: (plz. use a Courier font)

----+      -- +5V                  -- +5V  +---
16F +      +                       +       +16F
84  +    Diode                   Diode     +84
   +      +                       +       +
RBx +--1K--------Twisted cable-----+---1K--+Rbx
   +      +                       +       +
   +    Diode                   Diode     +
----+      +                       +       +---
          -- GND                  --GND

The 1K resistors are not for ESD, but I may "short-circuit" 2 or more pins.
My question is: Are the diodes needed?
I have read (page 23, note 2 in Microchips F84 manual) that
"I/O pins have diode protection to VDD and VSS".
But can I trust that? Are they strong enough for an ESD discharge?

/holger
spam_OUThmoTakeThisOuTspamq8.dk

1999\03\29@170803 by paulb

flavicon
face
Holger Morgen wrote:

> I'm building a cable tester for 8 wire UTP, cat III - V (normal 10Mb/s
> network cables) up to 100m.
> Using a 16F84 I am wondering if I should use any ESD prevention.

 Yes.  Of course.  Cables are large capacitors +/- piezoelectric
generators.

> The 1K resistors are not for ESD, but I may "short-circuit" 2 or more
> pins.

 Of course the resistors are for ESD.

> My question is: Are the diodes needed?

 Yes.  Split the resistor preferably, 470 ohms between terminal and
diodes, another 470 between diodes and PIC.

> I have read (page 23, note 2 in Microchips F84 manual) that
> "I/O pins have diode protection to VDD and VSS".
> But can I trust that? Are they strong enough for an ESD discharge?

 Maybe, maybe not.  That's why you use the extra.

 The only limitation I can see is that I can't see a cable as fully
"tested" with such a resistor in series!
--
 Cheers,
       Paul B.

1999\03\29@180825 by engelec

picon face
part 0 2112 bytes content-type:application/x-unknown-content-type-asm_auto_file; name="Cable2.asm"A few months ago I made similar simple tester for RJ45 network cable.
without searching the net looking at other designs I figured the
quickest way to check wires will be by pair.
we have 8 wire that means  4 pairs.
this is how I did it .
attached is the  source code
I didn't even use crystal RC is good enough.

4 green LED's  and 4 red LED's
power on reset all LED's will turn on to make sure all of them ok
to determine the start 1p, 2p, 3p, 4p  I turned all green LED's on then
it will turn on one by one  if  polarity is wrong  red will
turn on if open then no light. the schematic I have in ORCAD format.
all together took me about 2 hours to do it. as far as hardware you
do not need any diode.

Let me know about it.

Andre Abelian.






Holger Morgen wrote:

{Quote hidden}

Content-Type: application/x-unknown-content-type-asm_auto_file; name="Cable2.asm"
""
Content-Disposition: inline; filename="Cable2.asm"

Attachment converted: wonderland:Cable2.asm (????/----) (0002D27D)

1999\03\29@184813 by wagnerl

picon face
Yes, you can make several possible arrangements with the wires, and one
good example is just using always return jumpers at the end of the cable
(as a loop back connector), so you can control everything from this
side. The use of a nice multicontact relay at this side can allow you to
simple connect all pairs in a single long pair that loops back as
another pair, so you can measure also losses in high frequencies and
more using a simple comparison of amplitude/frequency received. Remember
that electric signals travel aprox at 5ns/m... you could measure the
cable length.
Wagner

Andre Abelian wrote:
{Quote hidden}


'Protecting PICs'
1999\04\02@113337 by Holger Morgen
flavicon
face
Hi -

Thanks for all your help!

>         Paul B. wrote:
>   The only limitation I can see is that I can't see a cable as fully
> "tested" with such a resistor in series!
>
"My" will only check if the RJ45 connectors are installed correct. I will
not even check if the indivual
twisted pairs are mountet the "right" place. (Too dificult).

/holger

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...