[plug] Dallas One Wire systems

[Timothy White]

>
> YMMV, but you may find that injecting a small external power source into
> your 1-wire system may be inevitable, and there are references to doing
> this.  This is because many UART16550 RS232 chips are only giving
> microamps of current through the port and the days of extracting power
> that way are long gone.  I say this from consultation with an
> electronics engineer who designs the sensors and data loggers that I
> build into systems for sale.  If you know what you're doing, or can find
> reference online, you're far better off considering the USB port, which
> is a serial transfer process, of course.

Anyone got circuit diagrams for the USB version then?? I see World
Wide Electronics has them for about $48 so that might be the way then.

>
> > As for locating these chips in Aust, I'm not doing too well yet, but I
> > guess research is all I can do, and if I do get a sample and they work
> > well, then start calling every electronics company to see if they will
> > do retail! I have found one company that is apparently a representing
> > for Dallas, but have yet to contact them.
>
> I don't know if it's the same selling scenario with all the 1-wire
> products versus just the "ibutton" range of 1-wire products, but I've
> found getting them wholesale is frustrating.  I got some from Farnell
> and also RS Components stock them.  Range is limited from those two.

Farnell and RS both have list prices much higher than wholesale
(MUCH), and higher than World Wide.

>
> IIRC, if you start from the Dallas website there are links to
> distributors in Oz.  I found that because the hardware is so cheap, most
> distributors I researched make money by bundling it with their own
> software solution, but YMMV.

I located Arrow Electronics that way, and while they don't do retail,
they did seem decently happy to do small orders for prototyping,
although it would take time to setup accounts etc etc. They pointed me
to World Wide who is a reseller for them, and while the prices are
much greater than Arrow Electronics, they do have them at the most
decent retail prices I've yet to find. Between $7 and $8 for chips I
want. Compared to the ~$3.50 that Arrow would wholesale them for, it's
not bad, and certainly better than the $13-$20 I could find elsewhere.

>
> As for the 1-wire weather station you mentioned in your OP, I remember
> reading on a weather watcher's forum in Oz that it can't and won't be
> imported into Oz for some reason, so you'll have to try buying it from
> USA suppliers.  Google is your friend.

Hmmm, how sad. Oh well, it was just one of those "it would be nice to
have" things.

>
> I'd be interested in you posting more updates here as you go because I
> am interested in the 1-wire products for commercial sales, but found it
> too hard to bother.  It looked as though I really had to develop a
> hardware/software product virtually from the ground up, and I'm not
> capable of doing that combo alone :-(  Maybe we could collaborate after
> you've done some more research - I need a good programmer on hand who
> can work with addressing minimalist, customised hardware setups ;-)

I'll certainly keep people updated. I've ordered a sample from Dallas,
which I believe will come from Arrow Electronics. So hopefully that'll
come, which'll save me about $40. Then it's time to locate some
electronics and try with the serial port, possibly with injected
power, or the usb if I get lazy :p

Tim
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