Re: one wire sensors

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 13 Jul 2007 20:51:05 GMT, andrew@xxxxxxxxxxxxxxxxxxxx (Andrew Gabriel)
wrote in message  <4697e5b9$0$648$5a6aecb4@xxxxxxxxxxxxxxxxx>:

>In article <ge8t83h1hsd1t5hlp0n5k0hnlnrabi82o8@xxxxxxx>,
>	Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> writes:
>>
>> 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. "
>
>Does that apply to the DS1820 family too?
>I use those around my home for temperature monitoring.

Presumably YES for the older, more buggy versions and NO for the newer ones.
They or their functional successors will presumably migrate to the larger
wafer.

I note that supplies of the 1-wire potentiometers have dried up completely
even in the secondary/tertiary supply chain.

I note too based on an article in the most recent hardcopy of the Maxim
Engineering Journal that the "1-wire" system has grown to 5 wires by the
addition of EN and DONE pins to complement the existing Data, Vcc and GND
pins.

These two new pins are used to "Regain Location Information by Leveraging the
1-wire Chain Function" which is "A Simple Signaling and Protocol Method
[that] Determines Device Physical Location".

Of course it doesn't do that either ;-) but it does establish the order of
the devices on the string. Folks with experience with one-wire devices may
have experienced the problem of not knowing which devices are where once
they've been installed.

This helps, but now most of the conductors (five) in a common (eight-wire)
CAT-5 cable are used rather than just "1-wire". That's three more wires than
are needed by plain ol RS-485 half-duplex with remote power and one more than
RS-485 with buss-supplied power.

... Marc
Marc_F_Hult
www.ECOntrol.org