Am 10.08.2014 20:39, schrieb Pedro Côrte-Real:
>
> I've now had 3 or 4 DS9490R adapters fail after bad weather. They
> seem to be particularly susceptible. After I swap them out the whole
> network is fine though.
>
They have a protective diode against lightning and other EMC inside, so
yes, that could make the adaptor fail but at the same time, it protects
the network. So if you use another adaptor *without* that diode, chances
are high random devices on the network will fail on next lightning
strike. The DS9490 is the part where failure is easy to detect and which
is most simple to replace.
If you have constant problems with lightning, think about opto-isolating
the onewire. There is a pure hardware solution
http://home.kpn.nl/thomas_7/1wire/1wire_isolating.html
by Thomas Rudolphi and another one featuring an ATtiny13 µC
http://sourceforge.net/projects/onewireoptocoupler/
and a small firmware which I have done for my own needs. Opto-Isolating
the USB is another possibility, but a bit overkill.
http://www.maximintegrated.com/en/app-notes/index.mvp/id/3891
Or use a cheap RS232 opto-isolator and an RS232-Onewire adaptor like the
DS9097U or the Link (not LinkUSB).
> Does anyone have any ideas on how to protect
> them or what good quality replacement USB 1wire masters there are?
>
The DS9490 is of good quality and there is no real replacement, the
other bus masters are mostly limited in speed. Though they may still fit
your needs.
When it comes to lightning strikes, I don't think any other adaptor will
do much better. Maybe it won't fail like the DS9490 but then that means
the network will fail in another, unpredictable way.
Kind regards
Jan
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