Go to Post We will be stressed, we will be angry. But we need to hold ourselves to a higher standard, we need to be role models and inspirations to students. - Andrew Schreiber [more]
Home
Go Back   Chief Delphi > Technical > Electrical
CD-Events   CD-Media   CD-Spy   FRC-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 03-10-2003, 01:03 PM
CBP at BAE's Avatar
CBP at BAE CBP at BAE is offline
Registered User
#0166 (Chop Shop)
 
Join Date: Mar 2003
Location: Merrimack, NH
Posts: 6
CBP at BAE is an unknown quantity at this point
Question Philosophy behind wiring rule C6...

I've searched the forum looking for a reason for rule C6 (below, for reference). I am puzzled by the need for the 10AWG wire to connect the controller to the device, regardless of the fact that the device may well have a smaller gauge wire to connect to (Globe motor comes immediately to mind). Why? Surely manufacturers of products that use these motors don't run excessively large conductors from the power source to the device. Or do they?

"C6 You must use 10 AWG or larger diameter wire for connections to and from the Speed Controllers if they are used with the Drill, CIM, Fisher-Price, Globe or Van Door motors. Even though the wires that are factory attached to these motors may be of a smaller size, the connection from the motor wires to the speed controllers must be as stated above."
__________________
Finalist: AutoDesk Animation Award
Winner: Granite State Regional Engineering Inspiration Award
Quarter-Finalist: Granite State Regional Competition
Quarter-Finalist: New England Regional Competition
Finalist: Rally in the Valley
Semi-Finalist: Mayhem on the Merrimack
Winner: BattleCry @ WPI
  #2   Spotlight this post!  
Unread 03-10-2003, 01:18 PM
Josh Hambright's Avatar
Josh Hambright Josh Hambright is offline
{Error Processing Custom Title}
AKA: oneangrydwarf/jtosh
no team (old school gangsta)
Team Role: Alumni
 
Join Date: Apr 2002
Rookie Year: 2000
Location: Indiana
Posts: 1,617
Josh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond reputeJosh Hambright has a reputation beyond repute
Send a message via AIM to Josh Hambright
We actualy melted the wire that was on the drill motor.

Literaly melted the solder and the electrical tape around it to insulate it.

Now granted that our drive system was having alot of problems and we were horribly inificant, fixed now, The wire was melted to...we ended up taking the old wire off and following first recommendation of not soldering to the leads, we just head shrinked a wire onto the motor that was 10 guage to try and prevent this from happening again...

This rule is pretty strange and doesn't make sense...alot like many other rules this year.
__________________
Former 461 Student/Mentor. Former 1272 and 1018 Mentor. Team 1555 Super-Fan.
Science and Engineering Can Open New Doors. --S.E.C.O.N.D.--
=~=!=@= #=$=%=
Co-Founder IndianaFIRST

Share your FIRST photos on Flickr!
  #3   Spotlight this post!  
Unread 03-10-2003, 04:47 PM
Unsung FIRST Hero
Mike Betts Mike Betts is offline
Electrical Engineer
no team
Team Role: Engineer
 
Join Date: Dec 2001
Rookie Year: 1995
Location: Homosassa, FL
Posts: 1,443
Mike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond reputeMike Betts has a reputation beyond repute
CBP:

The amount of current a wire can take is a function of the diameter (AWG) and the type/thickness of insulation. The type of insulation determines the temperature at which the wire will fail. The thickness (among other factors) determines the voltage at which the wire will suffer a dielectric breakdown and arc over.

The next thing to understand is that the wire generates heat when a current passes though it. With a "perfect" insulating jacket, the heat would never escape and the temperature would rise to infinity. All things being equal, the thicker the insulating jacket, the higher the temperature of the conductor will become before thermal equilibrium is established.

Now... Most all wire commonly available is either 300V or 600V wire. This includes the 10 AWG wire FIRST provides. The insulation is thick and heat builds up rapidly. Whereas the voltage rating of the wire on the motors is much less (it is custom built for the motor manufacturer) and less heat is built up.

With special, low voltage, Teflon (high temperature) wire, the motor leads could be made as small as 18 AWG or so (but this is expensive wire...).

Bottom line: FIRST has tried to be conservative and safe and still allow you to use readily available off the shelf wire. Please do not try and "second guess" without doing the engineering calculations which are verrrry messy (been there and done that).

Use the 10 AWG wire and move on to other problems you might have...

Mike Betts
Bobcat Robotics

Postscript to Mr. Dwarf:

I'm not sure what you have done but be sure to have an electrical engineer check it out. If you don't have an EE on your team, seek help from another team at your regional... I'm serious... It sounds like you have heat shrink tubing holding a 10 AWG wire on the motor terminal and that sure fire is a recipe for a failure.
__________________
Mike Betts

Alumnus, Team 3518, Panthrobots, 2011
Alumnus, Team 177, Bobcat Robotics, 1995 - 2010
LRI, Connecticut Regional, 2007-2010
LRI, WPI Regional, 2009 - 2010
RI, South Florida Regional, 2012 - 2013

As easy as 355/113...
  #4   Spotlight this post!  
Unread 03-11-2003, 06:37 AM
CBP at BAE's Avatar
CBP at BAE CBP at BAE is offline
Registered User
#0166 (Chop Shop)
 
Join Date: Mar 2003
Location: Merrimack, NH
Posts: 6
CBP at BAE is an unknown quantity at this point
Thanks for the answer...

Wasn't trying to change things, just wanted to know why. "Just because we say so" isn't good enuf for me

CBP@BAE - Merrimack HS Chop Shop
__________________
Finalist: AutoDesk Animation Award
Winner: Granite State Regional Engineering Inspiration Award
Quarter-Finalist: Granite State Regional Competition
Quarter-Finalist: New England Regional Competition
Finalist: Rally in the Valley
Semi-Finalist: Mayhem on the Merrimack
Winner: BattleCry @ WPI
  #5   Spotlight this post!  
Unread 03-11-2003, 06:38 AM
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 9,825
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
Quote:
Originally posted by Mike Betts
CBP:
The amount of current a wire can take is a function of the diameter (AWG) and the type/thickness of insulation. The type of insulation determines the temperature at which the wire will fail. The thickness (among other factors) determines the voltage at which the wire will suffer a dielectric breakdown and arc over.
Thanks Mike,
the type of insulation affects the current capability as interpreted by the electrical safety councils and the National Electrical Code (which in turn is driven by the insurance companies) and is mostly determined by it's melting point or the point at which the temperature of the wire is sufficient to melt the insulation and contact another conductor. The safety devices (breakers) must therefore open the circuit before the wire reaches that temperature based on known current heating, wire size and whether the conductors are in conduit or in free air. Since all wiring to motors on our robots are protected by 30 amp circuit delayed action circuit breakers, it follows that wiring should be capable of all characteristics of that type of protection. Using #16 wire to feed a Globe seems like an OK thing to do unless you consider that a moving part, pinching the wires might cause a short in the wire. It is conceivable that a #16 wire would set itself on fire before the breaker would open. Hence the rule.
Now many of you are going to bring up that the drill motor has #16 wires supplied and it has 129 amps at stall. Well, check the small printing on the wire and you will see that the insulation has a melting point of 105 C.
Many teams are reporting heating of the drill motors. As pointed out in these forums on many occasions and in the Robot docs, the drill motors are not designed to get rid of heat at low RPM. If you design your drive system such that maximum current is drawn at low RPM or near stall, the wire and the motor will reach temperatures at which the wiring, the brush assy, the soldered connections and/or the motor will fail. You must get the operating RPM on the motor into a more efficient range.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
All is better now, NOS parts are working fine. Why does this year's game remind me of Violet in Willie Wonka? Hmmmm, I see blueberries!
  #6   Spotlight this post!  
Unread 03-16-2003, 09:44 PM
Carl Owenby Carl Owenby is offline
Registered User
#0654 (Maclay Robotics)
 
Join Date: Jan 2003
Location: Tallahassee, FL
Posts: 24
Carl Owenby is an unknown quantity at this point
Sizing electrical conductors

Great question!

It is standard practice (National Electrical Code) to size the conductor based on the amperage rating of the overcurrent device (circuit breaker or fuse) used to protect the circuit, not the load connected to the circuit. The reason being that should the conductor short circuit, the overcurrent device will open before the conductor fuses or the insulation fails, possibly starting a fire. If you used a #16 AWG conductor and there was a short circuit, you could end up with 30 Amperes going through a conductor rated for

Typically, you will use #10 AWG on a 30 Amp circuit, #12 on a 20 Amp circuit and #14 on a 15 Amp circuit. Obviously, there are exceptions, such as the #18 AWG lamp cord that you plug into a 15 or 20 Amp receptacle.
__________________
There are 10 kinds of people in this world; those who understand binary and those who don't.
  #7   Spotlight this post!  
Unread 03-16-2003, 11:35 PM
sanddrag sanddrag is offline
back to school ;-)
FRC #0696 (Circuit Breakers)
Team Role: Teacher
 
Join Date: Jul 2002
Rookie Year: 2002
Location: Glendale, CA
Posts: 7,750
sanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond reputesanddrag has a reputation beyond repute
At Arizona some team's robot caught on fire (a few people thought it was part of the show). That's why you need to have a good electrical system. We have 8 guage finely stranded to everything that supplies current to the drive motors and 4 guage welding cable on our battery and to the breaker. We also have a huge ground terminal block for the drive motors and we use a connector rated for 200 Amps on our battery.
__________________
Teacher/Engineer/Machinist - Team 696 Circuit Breakers, 2011 - Present
Mentor/Engineer/Machinist, Team 968 RAWC, 2007-2010
Technical Mentor, Team 696 Circuit Breakers, 2005-2007
Student Mechanical Leader and Driver, Team 696 Circuit Breakers, 2002-2004

Support Team 696 on DonorsChoose!
  #8   Spotlight this post!  
Unread 03-17-2003, 05:05 PM
OddOne OddOne is offline
Registered User
#0990
 
Join Date: Feb 2002
Location: Las Vegas, Nevada
Posts: 12
OddOne is an unknown quantity at this point
Send a message via AIM to OddOne
Yah, that would me my team's robot that caught fire.... Turns out that the serial cable that we left on the teather port (stupid idea) shorted out when we tipped over (well, the tip caused something to cut the cable, so when I released the estop button, electricity came down the wire shorting it out.) surprisingly, the only thing that was damaged was that serial cable and some velcro was blackened. (I admit, that was a VERY VERY VERY stupid idea leaving the serial cable on there...)



---------------------------------------------
Fire on a robot causes great excitement and cheering from the crowd.
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
My Favorite rule. :) Useless member Rules/Strategy 15 02-28-2003 11:44 PM
Proposed New Rule M11 Joe Johnson Rules/Strategy 14 02-04-2003 01:41 PM
Rule C1 Justin Stiltner Rules/Strategy 9 01-05-2003 09:59 PM
Do away with the 2-minute rule! archiver 2000 3 06-23-2002 10:17 PM
1 coach rule Mike Soukup Rules/Strategy 14 01-07-2002 09:27 PM


All times are GMT -5. The time now is 02:40 PM.

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


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi