Post by thread:[EE]: does rs485 have to be run on twisted pair ?

i am planning on using category 5 wiring - is this possible ? its shielded but not twisted Paul Drummond spam_OUTgeniesysTakeThisOuTalphalink.com.au -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use .....listservKILLspam@spam@mitvma.mit.edu?bodyT%20PICList%20DIGEST

CAT 5 "UTP" - Unshielded Twisted Pair. Whatever you do, make sure you follow the 10Base-T pinout so you can use standard cables from the store! We didn't on a recent project and it's been a real pain to deal with. Andy Paul <geniesysKILLspamALPHALINK.COM.AU> on 09/27/2000 02:21:38 PM Please respond to pic microcontroller discussion list <.....PICLISTKILLspam.....MITVMA.MIT.EDU> To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU cc: (bcc: Andrew Kunz/TDI_NOTES) Subject: [EE]: does rs485 have to be run on twisted pair ? i am planning on using category 5 wiring - is this possible ? its shielded but not twisted Paul Drummond geniesysspam_OUTalphalink.com.au -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use @spam@listservKILLspammitvma.mit.edu?bodySET%20PICList%20DIGEST -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use KILLspamlistservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST

Are you sure you have Category 5 cable there ? Standard Cat 5 cable consists of 4 twisted pairs in a overall sheath. It is available with an overall shield but that is only used in difficult locations. If you take a length of cable apart you will find that each pair has a different number of twists per foot, the reason for this is to reduce the crosstalk between the pairs. RS485 works OK on Cat 5 cable. Just stick to the rules regarding termination. Regards Chris {Original Message removed}

I will deffineatly be using standard connections those little plugs have to be cheaper than screw connectors to...it is a very price concious project and l am having a hard time coming in on busget...even penny counts...personally l like it when l can say "what the heck, throw one of them in there too" but not on this job...thanks {Original Message removed}

hmm...thought it was cat 5 l had...must be something else...it has a sheath but not twisted pairs...some other data cable l guess...the bloke l got this bit off said it was cat 5...he obviously knows as much as me about the stuff. thanks...things are starting to fall into place... just got my free domain name which is cool so my website will be up soon...all going well... {Original Message removed}

Paul, What I meant was, the sequence of the signals across the connector might bite you. Get a copy of The Hardware Book (a WIndows .hlp file, I can e-mail it if you need) and check out the pinout for a LAN connection. It isn't obvious at first. Andy Paul <RemoveMEgeniesysTakeThisOuTALPHALINK.COM.AU> on 09/27/2000 02:57:31 PM Please respond to pic microcontroller discussion list <spamBeGonePICLISTspamBeGoneMITVMA.MIT.EDU> To: TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU cc: (bcc: Andrew Kunz/TDI_NOTES) Subject: Re: [EE]: does rs485 have to be run on twisted pair ? I will deffineatly be using standard connections those little plugs have to be cheaper than screw connectors to...it is a very price concious project and l am having a hard time coming in on busget...even penny counts...personally l like it when l can say "what the heck, throw one of them in there too" but not on this job...thanks {Original Message removed}

Paul Drummond wrote: i am planning on using category 5 wiring - is this possible ? its shielded but not twisted Further to my previous reply, I have just been reminded of the time I rigged a RS485 data link across a couple of fields using the barbed wire fencing. It did work - without problems. I hasten to add that it was a temporary installation. Regards Chris -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST

yeah send me that file if you could it would be a great help...how many pins does the connector have ? 8 ? if so it wont matter cause l can layout pcb to suit no ? anyway l will read the help file thanks again {Original Message removed}

----- Original Message ----- From: Chris Carr <nyedEraseME.....BTINTERNET.COM> To: <EraseMEPICLISTMITVMA.MIT.EDU> Sent: Wednesday, September 27, 2000 2:16 PM Subject: Re: [EE]: does rs485 have to be run on twisted pair ? {Quote hidden}> Paul Drummond wrote: > > > i am planning on using category 5 wiring - is this possible ? > its shielded but not twisted > > Further to my previous reply, I have just been reminded of the > time I rigged a RS485 data link across a couple of fields using > the barbed wire fencing. > > It did work - without problems. > I hasten to add that it was a temporary installation. Now, that's a sharp idea. > Regards > Chris > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > use RemoveMElistservEraseMEEraseMEmitvma.mit.edu?body=SET%20PICList%20DIGEST > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservspam_OUTKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST

You might also want to take a look at this http://www.arcelect.com/10baset.htm I once had a VERY long argument with a telco guy on a job about CAT5, twisted pairs and pin layout of the RJ45 connector. This page explains the various uses and pinouts for the RJ45/CAT5 combination. Tobie {Original Message removed}

> Paul, > > What I meant was, the sequence of the signals across the connector might bite > you. Get a copy of The Hardware Book (a WIndows .hlp file, I can e-mail it if > you need) and check out the pinout for a LAN connection. It isn't obvious at > first. > Or find it online at: http://www.hardwarebook.net/co_Ethernet10BaseT.html -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservTakeThisOuTspammitvma.mit.edu?body=SET%20PICList%20DIGEST

At 04:21 AM 9/28/00 +1000, Paul wrote: >i am planning on using category 5 wiring - is this possible ? >its shielded but not twisted > >Paul Drummond >EraseMEgeniesysspamspamBeGonealphalink.com.au Other way around, Paul. Cat 5 cable is 4 twisted pairs. It us usually NOT shielded, although I have seen some special order cables that were. And yes, Cat 5 cable is ideal for RS485. dwayne Dwayne Reid <RemoveMEdwaynerKILLspamplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 16 years of Engineering Innovation (1984 - 2000) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use listservSTOPspamspam_OUTmitvma.mit.edu?body=SET%20PICList%20DIGEST

Category 5 *IS* twisted - each pair is twisted a slightly different number of times per foot so that they won't re-radiate into each other pair with any great strength. You do understand why RS422 and RS485 differential signalling is used, don't you? -[as the two wires *ALWAYS* have opposite signals and they pass through all interfering fields equally then any induced signal just lifts both wires' voltages up (or down) the same amount. The (equal in both wires) interference is then easily rejected by the receiver circuitry.] *DON'T* use shielded cable for RS422 or RS 485, it's just a waste of money. Bye. > {Original Message removed}

> >You do understand why RS422 and RS485 differential signalling is used, don't >you? -[as the two wires *ALWAYS* have opposite signals and they pass >through all interfering fields equally then any induced signal just lifts >both wires' voltages up (or down) the same amount. The (equal in both >wires) interference is then easily rejected by the receiver circuitry.] >*DON'T* use shielded cable for RS422 or RS 485, it's just a waste of money. Depends who wired the cable.. Around the local university, the comp services people think that as long as the colors are in the same order on the other end of the cable, it dosen't matter. So, they probably have some cables where pair A is inter-twisted with pair B. Never a good idea, as those TV indigestion commercials will tell you. Never get your A's mixed up with your B's. -- Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use spamBeGonelistservSTOPspamEraseMEmitvma.mit.edu?body=SET%20PICList%20DIGEST

Paul, I've created several RS485 devices with the PIC and connected them using twisted Cat-5 cable. I put the devices online about a year ago and haven't touched them since. Not one hiccup!!! Jason Mielke Chief Engineer Bliss Communications, Inc. KILLspamjayspamBeGoneticon.net ____________________________________________ WCLO/WJVL WBKV/WBWI WRJN/WEZY WFHR/WGLX -------------------------------------------- -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use EraseMElistservEraseMEmitvma.mit.edu?body=SET%20PICList%20DIGEST

At 09:29 PM 09/27/2000 , you wrote: >Paul, >I've created several RS485 devices with the PIC and connected them using twisted Cat-5 cable. I put the devices online about a year ago and haven't touched them since. Not one hiccup!!! > >Jason Mielke >Chief Engineer >Bliss Communications, Inc. >@spam@jay@spam@spam_OUTticon.net Jason, Which RS485 chips did you use? I am designing a small RS485 Pic Network. Brian -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use spamBeGonelistservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST

Brian, I used the Max485. I've been told that there are other brands that are better, but I haven't had a failure yet. The network I designed is for controlling several satellite receivers and an audio switcher 3 miles away from a radio studio. It works pretty good. The first device in the system is an RS232 to RS485 converter with RS485 addressing implemented. It runs on a PIC16c74a. I decided not to even use the serial port within the chip, instead I ran it at 20MHz and bitbanged in and out at 9600 baud. The other devices are LCD display devices and button panels with LED's on them. All of these devices are scattered throughout a radio broaccast facility. The next versions of the converters will use the Max 3110 and Max 3140 (if Digikey will ever carry them)! Jason {Quote hidden}> Jason, > > Which RS485 chips did you use? I am designing a small RS485 Pic Network. > > Brian > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > use .....listservspam_OUTmitvma.mit.edu?body=SET%20PICList%20DIGEST > > > > - -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-request.....TakeThisOuTmitvma.mit.edu

Paul Drummon wrote: > hehe...sounds like something l'd do... > must be pretty good then... > its amazing the signals didnt get stuck on the barbs though > LOL ;-) Yeh, those quarter wave stubs are a real bugger when you up the transmission rates to optical levels 8-) Chris > {Original Message removed}

As far as I know, it does not have to be run on a twisted pair, but it usually is so that any distortion that is applied to one line is applied to both, this distortion can then be filtered out at the recieving end. If you have the wires close enought together, I don't see why it should make too much difference if they are twisted or not. Mark Hankins ===== Please take a while to visit this page: http://www.geocities.com/markosaurus/index.html ____________________________________________________________ Do You Yahoo!? Get your free @yahoo.co.uk address at http://mail.yahoo.co.uk or your free @yahoo.ie address at http://mail.yahoo.ie -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestKILLspamspammitvma.mit.edu

> If you have the wires close enought together, I don't > see why it should make too much difference if they are > twisted or not. Wires are twisted so that each wire in the pair has the same coupling to the external environment. You want all external noise to be common mode so that it can be largely removed in the process of detecting the differential mode signal. Even close parallel wires can pick up more differential noise than a twisted pair. This can happen especially when the noise sources or anything that effects an electric field is nearby. Consider the difference in capacitance between one wire 1mm from a conductive plate, and similar wire 2mm from the same conductive plate. ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, .....olinRemoveMEcognivis.com, http://www.cognivis.com -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

Try this a a RC osc for a pic16F84 ect. 1. first take a frequency measument at osc out 2. next solder two wires about 2"in long across the cap and twist them after two or more turns Check the frequency out. who about that for fine tuning the frequency Regards Art Where's dave? seen his car in the car Park? or does he live in that mansion with the pool. he as't moved for over 16 hours. {Original Message removed}

>I rigged a RS485 data link across a couple of fields using >the barbed wire fencing. >It did work - without problems. >I hasten to add that it was a temporary installation. You weren't working in the Aussie outback were you? I have heard many stories of 1 wire telephone lines using a wire in a fence and the ground as the return!! -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use spamBeGonelistserv@spam@spam_OUTmitvma.mit.edu?bodyT%20PICList%20DIGEST

>its amazing the signals didnt get stuck on the barbs though >LOL ;-) They were the spark gaps for the lightning strike. Sorry my messages are so late after the thread - have just come back from a week away. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use TakeThisOuTlistservspammitvma.mit.edu?bodyT%20PICList%20DIGEST

>Cat 5 cable is 4 twisted pairs. It us usually NOT >shielded, although I have seen some special order >cables that were. Normal CAT5 cable is called UTP for "unshielded twisted pair" but it is also possible to get STP for "shielded twisted pair" I have never had to use STP, but I imagine if doing wiring in a noisy environment like a machine shop it may be necessary. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use listservEraseMEmitvma.mit.edu?bodyT%20PICList%20DIGEST

> yeah send me that file if you could it would be a great > help...how many pins > does the connector have ? 8 ? > if so it wont matter cause l can layout pcb to suit no ? > anyway l will read the help file thanks again I believe it is pins 1 and 6 and pins 2 and 3. The others aren't used by Ethernet so one doesn't really have any idea how a stock cable would hook them up. TTYL -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservEraseMEspam_OUTmitvma.mit.edu?body=SET%20PICList%20DIGEST

>I rigged a RS485 data link across a couple of fields using >the barbed wire fencing. >It did work - without problems. >I hasten to add that it was a temporary installation. You weren't working in the Aussie outback were you? I have heard many stories of 1 wire telephone lines using a wire in a fence and the ground as the return!! Actually Alan that's where I got the idea from. It was the method we used as a temporary repair to a phone when the overhead lines were brought down by a winter storm. This was back in the 60's and up the Yorkshire Dales, we still had manual magneto exchanges in those days. The heater of a Morris Minor Van leaves a lot to be desired 8-) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use @spam@listservRemoveMEEraseMEmitvma.mit.edu?body=SET%20PICList%20DIGEST