Re: one wire sensors

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Wed, 08 Aug 2007 20:41:52 -0700, Too_Many_Tools <too_many_tools@xxxxxxxxx>
wrote in message  <1186630912.450837.156390@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>On Jul 6, 3:26 pm, Marc_F_Hult <MFH...@xxxxxxxxxxxxxxxxxxxxx> wrote:

>>
>> I'd be wary of _depending_ on Dallas / Maxim 1-wire for new applications.
>>
>> The Applications Engineer for the 1-Wire and iButton Groups wrote me :
>>
>> "It is correct that the DS2890 was recently assigned a NRFND status.  Our
>> customer base on this product is very small and ongoing R&D investment is
>> large and prohibitive to convert the 6" wafer based design to an 8"
>> wafer equivalent that is necessary to continue production in our wafer
>> fabs.Our EOL strategy for this device is to build a supply of product that
>> will provide a 5yr to 7yr supply to existing customers. "
>>
>> Nonetheless, I've developed a family of pcboards that provide signal
>> conditioning, power supply and analog, digital, and 1-wire connectivity
>> for what I call THOL (Temperature, Humidity, Occupancy and Lighting). They
>> are designed to fit in single gang switch box for wall or ceiling
>> mounting, are connected to a multiplexor at one or more central locations
>> for logging via  DMX, 1-wire and PC-PCI 16-bit AD converters.
>
>So what is the alternative if the 1-wire is history?
>
>TMT

Well, the first word of this sentence is also "history" , but you read it ;-)

No doubt there will continue to be 1-wire products and I didn't mean to imply
otherwise. What I meant to convey was that one should not assume that all the
1-wire products would continue to be available because some, including at
least one that Maxim continues to promote through its application notes, is
no longer available even on the secondary market and the Applications
Engineer for 1-wire offered no hope for a replacement.

The conventional crystal ball typically has tantalizing images of nano-power
devices using RF communication meshes that are inexpensive and widely
available. Some will harvest / scavenge energy for operation from vibrations
and light temperature differentials and so will be mostly independent of
external power. See for example,
http://www.edn.com/index.asp?layout=article&articleid=CA6459064

And systems that became 'history' a long time ago will continue to be useful.
I recently purchased a new Comtrol Ethernet to 32-port serial converter on
eBay for ~$5/port in which each of the 32 ports is independently configurable
with software to be RS-232, RS-422, or RS-485. These 'legacy' last-leg
hardware links make 'legacy' RS-xxx devices in my home accessible from
anywhere in the world where an Internet connection is available. It uses RJ45
connectors so in combination with Power Over Cat5, and the extensive CAT5
wiring in my house, I can control  RS-xxx devices in different place in the
house as easily as plugging into a CAT5 jack. I do need to remember not to
plug them into an ethernet router  ;-)

One might note that the new INSTEON 2412S 'modem' is available only in a
RS-232/TTL version and not USB. IMO, and apparently that of SmartLabs, RS-232
is more flexible for this role than USB (see paragraph above).

... Marc
Marc_F_Hult
www.EControl.org