Go to Post Could you explain this concept of a break from FIRST? Did my wife put you up to this? - Gary Dillard [more]
Home
Go Back   Chief Delphi > Technical > Electrical
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
 
 
Thread Tools Rate Thread Display Modes
Prev Previous Post   Next Post Next
  #15   Spotlight this post!  
Unread 26-09-2016, 16:17
wireties's Avatar
wireties wireties is offline
Principal Engineer
AKA: Keith Buchanan
FRC #1296 (Full Metal Jackets)
Team Role: Mentor
 
Join Date: Jan 2006
Rookie Year: 2004
Location: Rockwall, TX
Posts: 1,169
wireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond reputewireties has a reputation beyond repute
Send a message via AIM to wireties
Re: Can I branch the CAN to go to two separate places?

Quote:
Originally Posted by ratdude747 View Post
QFT. Any time termination matters (such as CAN), you've entered the wonderful world of RF where reflections and the like are real. In RF you get to throw away everything you know about electricity and circuits, aside from Kirchoff's laws. Ohm's law? Kiss it goodbye, it doesn't apply any more. Wire spacing and twist rate do matter a ton.
All the normal rules still apply but there are additional rules (terms in the equations). You are looking at the complex impedance of the load (which did not factor in at low frequencies) rather than simple resistance. The size and shape of the wire and connector pins all matter because they help determine the reactance portion of the impedance (resistance plus reactance). Balancing the impedance of the source and the load become important to reduce mismatches that can cause ringing (reflected waves bouncing around willy-nilly).

So for CANbus the sources have a particular output impedance that performs best when the load has a matching impedance (same resistance and opposite reactance). To keep things simple use wire much like the green/yellow that comes with the Talons. Use connectors with cross sections close to the cross section of the wire. Wire things in series from source to load (like CTE recommends and the CANbus standards dictate). Use a 100-ish ohm resistor for the load (termination). To do otherwise is to ask for troubles that are very difficult to diagnose.
__________________
Fast, cheap or working - pick any two!

Last edited by wireties : 26-09-2016 at 16:20.
Reply With Quote
 


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 01:55.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi