Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Paul E Bennett Newsgroups: comp.arch.embedded Subject: Re: Sensor wiring Date: Tue, 01 Oct 2013 09:19:41 +0100 Organization: Hidecs Consultancy Lines: 42 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Trace: individual.net lppEFQpXDRisbWbxK38OvgVGoi+0PhUz2VNU1oCTDO4egem8bo Cancel-Lock: sha1:GTb/cucYwjgweFkQKPkMVubWpVI= User-Agent: KNode/4.10.5 Xref: csiph.com comp.arch.embedded:14043 Mel Wilson wrote: > I want an I2C connection between a Raspberry Pi and an ATtiny85 over 35m > of > buried wire. Any guidelines for signal conditioning and protection? > Acknowledging that out-of-spec bits per second is a definite possiblity. > > Thanks, Mel. Hi Mel, I have just seen this and note you already had quite a few responses. The sort of distance you are going I would definitely say that I2C is not the long range interconnect you ould want. Galvanic Isolation and Transient Protection is going to be required for both ends of the link. If you also need power fed to the instrument end then this has also to be figured in and similarly protected if it is other than a mains supply. In which case I would look at either opto-isolator or transformer coupled connections. It is easy to recreate the I2C electrical conditions at each end of the isolated link. What you use in between should be given careful consideration but just raising the voltage level of the signals and employing appropriate protective zener/varistor/capacitor clamping and filtering with energy controlling resistors will be the route I would take. You can use a cable with a screened twisted pair for each line and even a third one for the low-power feed if you need it (3 pair cable by Belden would probably suit if you have a suitable conduit for the cable to go through). If you had mentioned the sort of data rate you were interested in it would have been easier to suggest something more specific. -- ******************************************************************** Paul E. Bennett IEng MIET..... Forth based HIDECS Consultancy............. Mob: +44 (0)7811-639972 Tel: +44 (0)1235-510979 Going Forth Safely ..... EBA. www.electric-boat-association.org.uk.. ********************************************************************