Issue with communication distances

Tintin

Hi all,

I'm thinking of using·three DS2760's to read temperatures from three thermocouples to control concrete curing.· These thermocouples·would be insterted at different locations, some of which could be up to 100 feet away from the stamp microcontroller.· I already know that thermocouples can't extend that far, so the DS2760 must·be placed·close to the thermocouple.··To ensure reliable communication between the stamp and the DS2760·(up to 100 feet away) what should be done?

Thanks for your help,

Frank·····

Kevin Wood

I was looking at the iButton site a few weeks ago, and I saw a similar application mentioned. Here is the link:

www.maxim-ic.com/products/ibutton/applications/index.cfm?Action=DD&id=27

I haven't used an iButton; from other postings on the forum, my understanding is that you can get long distances between 1-wire devices.

Tintin

Wow, this ibutton stuff seems really promising.· Thanks for the pointer!·

Mike Green

The iButton and other 1-Wire stuff can be made to work over distances on the order of hundreds of feet, but you have to be very careful about signal levels, noise, and cabling. The iButton/1-Wire site has lots of articles on how to make this work -- read them and follow their suggestions. The built-in commands of the Stamps probably won't work over more than a few feet with the "bare I/O pin" and you'll need some kind of external driver, mostly to ensure that the low to high transitions are fast and clean enough over those distances and that the 1-Wire can supply enough power. Again, there are plenty of tested suggestions on how to do this. I've only used the 1-Wire protocol over short distances with about 20-30 devices attached, but I read nearly every application note before I started hooking things up.