Go to Post Yes, I have lost it! - Alan Anderson [more]
Home
Go Back   Chief Delphi > Technical > Programming
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 01-05-2006, 16:38
Mark McLeod's Avatar
Mark McLeod Mark McLeod is online now
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,721
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
CMU Power & 7.2v Circuit

Just an interesting addendum to the camera power cycling problem - the one where if it doesn't initially power up properly then you must cycle the camera power to get it going again.
We experienced a particular variation of this problem only once in Atlanta, and that was in the pits during a systems check.

For most teams a simple cycling of the robot power fixes the problem, however, if you are using the IFI backup charging circuit as is, then when the 12v source is cut off, and the backup power is off, the 7.2v battery leaves enough of a charge via feedback through the breaker panel into the RC that power to the camera is not cutoff when you throw the main breaker.
When this happens the only way to cut off power to the camera altogether is to disconnect the 7.2v battery (or try to figure out if it's legal to add a diode to block current flow back into the 12v circuits).

P.S. I edited slightly to try correcting the impression that the RC was purposely running off backup power.
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle

Last edited by Mark McLeod : 02-05-2006 at 13:33.
  #2   Spotlight this post!  
Unread 02-05-2006, 12:47
Keith Watson Keith Watson is offline
Registered User
FRC #0957 (WATSON)
Team Role: Mentor
 
Join Date: Feb 2006
Rookie Year: 2006
Location: Wilsonville, OR
Posts: 112
Keith Watson is just really niceKeith Watson is just really niceKeith Watson is just really niceKeith Watson is just really nice
Re: CMU Power & 7.2v Circuit

After turning off the main 12v supply, the reset button will turn off the 7.2v supply. This is in the manual.
__________________
Keith Watson - Professional Software Engineer
No relation to "Kevin" Watson, who created the camera tracking code.
  #3   Spotlight this post!  
Unread 02-05-2006, 13:15
Mark McLeod's Avatar
Mark McLeod Mark McLeod is online now
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,721
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: CMU Power & 7.2v Circuit

Quote:
Originally Posted by Keith Watson
After turning off the main 12v supply, the reset button will turn off the 7.2v supply. This is in the manual.
This is beyond the manual.
You seem to be thinking of how the reset button will turn off the RC when it's powered solely by the backup battery after you've cut the main power. The Master processor will also cut backup power after about 3 seconds. That's not the issue I'm bringing up here. I'll try to state the issue I'm warning about more clearly.

It's the interaction of the camera and the IFI backup circuit in particular that complicates matters in that when the main power is off, the circuit as designed (lacking a diode) allows power from the backup battery to bleed into the main breaker panel (there is no off-switch). From there it supplies power to the RC through the 12v terminals, bypassing the normal 7.2v power input.

At such low power the RC doesn't actually run (although you do get some faintly glowing status lights), but the trickle of power extends to the I/O pins.
This isn't an issue for most sensors, however, the camera receiving power from the RC pins seems to get just enough to prevent it from fully cycling the camera power. It's not usually noticeable and doesn't affect normal camera operation. I've only experienced it once in three competitions. It's only a problem if the camera doesn't power up the first time properly and requires a full power reset.

Most teams I've seen using the camera didn't incorporate a visible camera status indicator. We use a rapidly blinking light to indicate the camera is not working/communicating that goes solid when the camera is operational, so it was easy to see when the problem occurred and easy to diagnose.
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle

Last edited by Mark McLeod : 03-05-2006 at 08:32.
  #4   Spotlight this post!  
Unread 02-05-2006, 15:19
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,766
Al Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond repute
Re: CMU Power & 7.2v Circuit

Mark,
I thought this would be a problem that would just drain the backup. I never thought it could back feed enough current to keep the camera up. A redesign with a steering diode is definitely warranted for next year.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
Closed Thread


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
No power - no problem P1h3r1e3d13 General Forum 2 20-02-2006 07:18
Circuit design help - power supply - Non FIRST Josh Siegel Electrical 31 24-12-2005 13:47
the best power regulator John Gutmann Electrical 37 04-08-2005 08:52
Direct 7.2v power from the wall... Ferazel2001 Electrical 1 31-01-2004 17:49
Max mechanical power of motors, how is it useful? Ken Leung Motors 1 09-11-2001 14:15


All times are GMT -5. The time now is 10:33.

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