SV: [basicstamps] iButton io protection
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Posts: 46,084
Greetings!
What you need is the DS9503 ESD protection chip.
Basically, it's a Zener together with 2 5Kohm and should be able to
withstand electrostatic discharges of up to 27KV...
As for the short circuit problem...
Just read the status of the port before using the OWOUT command.
after all, the pin is supposed to show a logic '1' because of the pull-up
resistor.
:-)
Trygve
Opprinnelig melding
Fra: De Meester, Michel [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tHOLaBDxVOBWL2toWizhIEK-CHc_nJj5JHND37QgJeNrh9MGic5vzTZQS_sQkWtloPQCzUw0MH8T0vqBal039CNXqtvXLCc]Michel.De.Meester@u...[/url
Sendt: 24. juli 2002 09:26
Til: 'basicstamps@yahoogroups.com'
Emne: [noparse][[/noparse]basicstamps] iButton io protection
Hello Stampers
Hi guys, it has been a while but I'm back in Stamp business :-))
I hooked up a Dallas iButton probe DS9092 (
http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=2974 ) to the io pin of a
BS2P40 used in an entrance control circuit.
The 4.7k pullup resistor is in place and I can read the code embedded in the
serial number iButton DS1990A (
http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=2829 )
I hear you thinking, so what the heck is the problem, well, because this
system will be used in a 12 volt car environment, I want to protect the io
pin against a lot of situations:
- shortning the reader (the input will be pulled down to GND) while the
OWOUT command sends data to the iButton
- putting 12 volt (or any other voltage) between the outer and inner "ring"
of the reader (a iButton like battery or similar, a miswiring etc.)
I already tried a 1k resistor between the io pin and the pullup resistor but
then I can't read the iButton anymore.
Does anybody knows a good protection circuit (I already toasted an io port
on the BS2P40) so the iButton reader is a bit vanalism proof.
Thanks in advance
Michel
Met vriendelijke groetjes,
> ************************************************
> Michel De Meester
> Biotechnisch Onderhoud
> Universitair Ziekenhuis Antwerpen
> Wilrijkstraat 10
> 2650 Edegem - B
> tel: ++32 (0)3 821 36 47
> e-mail: michel.de.meester@u...
>
> *************************************************
>
>
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What you need is the DS9503 ESD protection chip.
Basically, it's a Zener together with 2 5Kohm and should be able to
withstand electrostatic discharges of up to 27KV...
As for the short circuit problem...
Just read the status of the port before using the OWOUT command.
after all, the pin is supposed to show a logic '1' because of the pull-up
resistor.
:-)
Trygve
Opprinnelig melding
Fra: De Meester, Michel [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tHOLaBDxVOBWL2toWizhIEK-CHc_nJj5JHND37QgJeNrh9MGic5vzTZQS_sQkWtloPQCzUw0MH8T0vqBal039CNXqtvXLCc]Michel.De.Meester@u...[/url
Sendt: 24. juli 2002 09:26
Til: 'basicstamps@yahoogroups.com'
Emne: [noparse][[/noparse]basicstamps] iButton io protection
Hello Stampers
Hi guys, it has been a while but I'm back in Stamp business :-))
I hooked up a Dallas iButton probe DS9092 (
http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=2974 ) to the io pin of a
BS2P40 used in an entrance control circuit.
The 4.7k pullup resistor is in place and I can read the code embedded in the
serial number iButton DS1990A (
http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=2829 )
I hear you thinking, so what the heck is the problem, well, because this
system will be used in a 12 volt car environment, I want to protect the io
pin against a lot of situations:
- shortning the reader (the input will be pulled down to GND) while the
OWOUT command sends data to the iButton
- putting 12 volt (or any other voltage) between the outer and inner "ring"
of the reader (a iButton like battery or similar, a miswiring etc.)
I already tried a 1k resistor between the io pin and the pullup resistor but
then I can't read the iButton anymore.
Does anybody knows a good protection circuit (I already toasted an io port
on the BS2P40) so the iButton reader is a bit vanalism proof.
Thanks in advance
Michel
Met vriendelijke groetjes,
> ************************************************
> Michel De Meester
> Biotechnisch Onderhoud
> Universitair Ziekenhuis Antwerpen
> Wilrijkstraat 10
> 2650 Edegem - B
> tel: ++32 (0)3 821 36 47
> e-mail: michel.de.meester@u...
>
> *************************************************
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/