Go to Post This thread is just as lethal as any design your own game thread. - Schnabel [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

 
Closed Thread
Thread Tools Rating: Thread Rating: 4 votes, 5.00 average. Display Modes
  #46   Spotlight this post!  
Unread 24-05-2005, 12:39
WizardOfAz's Avatar
Happy Birthday! WizardOfAz WizardOfAz is offline
Lead Mentor
AKA: Bill Bennett
FRC #1011 (CRUSH)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Tucson, AZ
Posts: 101
WizardOfAz will become famous soon enough
Send a message via AIM to WizardOfAz
dummy load / test load for Victor speed controller

We'd like to build a test setup for the Victors. Anybody have a suggestion for a cheap fixed resistance dummy load? I don't want to use a motor because the motor is not fixed resistance and it's hard to measure motor power output. Would like to have the ability to set the resistance to about 0.32 ohms to get a 40 A max current test, and also to something like 2.5 ohms for a 5 A max current test. Would like to use a fixed resistor that would spread the heat dissapation over a large area so it doesn't get dangerously hot (500+ watts for the 40 A test).

I can put a big resistor in a can of oil like we do in RF power testing. Anybody got a better idea?

Bill
  #47   Spotlight this post!  
Unread 24-05-2005, 13:59
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
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: 8,867
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: Victor Burnouts

I passed your query on to one of our electrical sub-system mentors.
Our electrical group mostly use the ribbon-style power resistor with a fan blowing on it. The ribbon style are easier to get, cheaper and take a lot of abuse. Between Ebay and online surplus vendors, this can be done on the cheap.
http://www.milwaukeeresistor.com/pdf/ribwound.pdf

There is a chassis mount style which one of our electrical mentors has used at work as well. These are aluminum cased and can be mounted to a finned or water cooled plate, but are more expensive.
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle

Last edited by Mark McLeod : 24-05-2005 at 14:01.
  #48   Spotlight this post!  
Unread 24-05-2005, 14:02
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: 10,798
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: dummy load / test load for Victor speed controller

Quote:
Originally Posted by WizardOfAz
We'd like to build a test setup for the Victors. Anybody have a suggestion for a cheap fixed resistance dummy load? I don't want to use a motor because the motor is not fixed resistance and it's hard to measure motor power output. Would like to have the ability to set the resistance to about 0.32 ohms to get a 40 A max current test, and also to something like 2.5 ohms for a 5 A max current test. Would like to use a fixed resistor that would spread the heat dissapation over a large area so it doesn't get dangerously hot (500+ watts for the 40 A test).

I can put a big resistor in a can of oil like we do in RF power testing. Anybody got a better idea?

Bill
How about a 500' roll of #10. An RF load would not get you to the current you want to draw but you could parallel 10 resistors, 5 ohm at 10 watt and drop them in the oil for cooling and be OK I bet.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
  #49   Spotlight this post!  
Unread 24-05-2005, 14:23
BrianBSL BrianBSL is offline
Registered User
FRC #0190
 
Join Date: Sep 2004
Rookie Year: 2000
Location: Worcester, MA
Posts: 251
BrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud of
Re: dummy load / test load for Victor speed controller

Quote:
Originally Posted by WizardOfAz
We'd like to build a test setup for the Victors. Anybody have a suggestion for a cheap fixed resistance dummy load? I don't want to use a motor because the motor is not fixed resistance and it's hard to measure motor power output. Would like to have the ability to set the resistance to about 0.32 ohms to get a 40 A max current test, and also to something like 2.5 ohms for a 5 A max current test. Would like to use a fixed resistor that would spread the heat dissapation over a large area so it doesn't get dangerously hot (500+ watts for the 40 A test).

I can put a big resistor in a can of oil like we do in RF power testing. Anybody got a better idea?

Bill
For discharging our Prius battery packs for our electric airplane project, we use 6 electric water heater elements in a trashcan full of water. Unfortunately, I think their resistance is somewhere around 10-15 ohms, which wouldn't be very doable to achieve .32 ohms.
  #50   Spotlight this post!  
Unread 24-05-2005, 16:19
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: 1,442
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
Re: Victor Burnouts

A long time ago, we tested fuel cells by placing two electrical plates into a small swimming pool filled with water and then added rock salt until the resistance was what we wanted. I'm sure that a small garbage can could be used in this case. Some experimentation is required and must be done in a ventilated area (possibility of electrolysis).

Mike
__________________
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...
  #51   Spotlight this post!  
Unread 24-05-2005, 17:57
WizardOfAz's Avatar
Happy Birthday! WizardOfAz WizardOfAz is offline
Lead Mentor
AKA: Bill Bennett
FRC #1011 (CRUSH)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Tucson, AZ
Posts: 101
WizardOfAz will become famous soon enough
Send a message via AIM to WizardOfAz
Victor load testing

This sure provoked some interesting suggestions! My favorite is the salt water swimming pool...

At lunch I went over to the electronics store and bought 10 3.6 ohm 25 watt resistors. We'll wire them in parallel, in two banks of 5 each, so we can test with either (approx) 450 or 225 watts load at full power (12.8 volts). This should give a max current through the Victor of about 36A, a reasonably safe 10% below max rating for it. These are rectangular concrete resistors, so we can cool them with a slab of steel laid across all of them that will have pretty good surface contact, and keep the full power tests reasonably brief, since at max the resistors will be dissipating about 46 watts of heat each, substantially over their 25 watt rated limit. The steel will also protect from the shrapnel if they blow up....

Thanks again for the ideas.

Bill
  #52   Spotlight this post!  
Unread 24-05-2005, 21:57
gburlison gburlison is offline
Mentor
FRC #0662 (Rocky Mountain Robotics)
Team Role: Mentor
 
Join Date: Sep 2002
Rookie Year: 2000
Location: Colorado Springs, CO
Posts: 245
gburlison is a name known to allgburlison is a name known to allgburlison is a name known to allgburlison is a name known to allgburlison is a name known to allgburlison is a name known to all
Re: Victor load testing

I remember seeing a DIY battery tester that used steel banding for the load. A suitable length of steel banding that is used to secure crates was attached to a piece of plywood in a zigzag pattern. The resistance might ba a little low for this project though.
__________________
Gordon Burlison - Mentor
662/Rocky Mountain Robotics
"Every silver lining's got a Touch of grey - Robert Hunter"
"No sense in being pessimistic, it wouldn't work anyway"
  #53   Spotlight this post!  
Unread 24-05-2005, 22:43
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: 10,798
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: Victor load testing

Quote:
Originally Posted by WizardOfAz
This sure provoked some interesting suggestions! My favorite is the salt water swimming pool...

These are rectangular concrete resistors, so we can cool them with a slab of steel laid across all of them that will have pretty good surface contact, and keep the full power tests reasonably brief, since at max the resistors will be dissipating about 46 watts of heat each, substantially over their 25 watt rated limit. The steel will also protect from the shrapnel if they blow up....
Bill
Bill,
I would add a fan to your setup blowing under the steel plate. 25 watt resistors are conservative rating in an enclosed space so with the plate and fan you should be OK for the dissipation. Of course, if you wanted to go the "swimming pool" route, a trip to the store for a couple of gallons of distilled water should add some margin of safety. Pure distilled water does not conduct and is easier to dispose of than mineral oil. When you are done, just add some coffee or tea, sugar and cream to taste, donuts optional.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
  #54   Spotlight this post!  
Unread 09-12-2005, 08:04
colin340 colin340 is offline
human
AKA: Colin Nobles
FRC #0148
Team Role: Teacher
 
Join Date: May 2005
Rookie Year: 2005
Location: rochester
Posts: 432
colin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond reputecolin340 has a reputation beyond repute
Send a message via AIM to colin340
Re: Victor Burnouts

we had to change 3 Victor right be for a demo, we were getting shocked very badly we think think static was the problem. is there a good legal way to ground the robot
  #55   Spotlight this post!  
Unread 09-12-2005, 10:41
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: 10,798
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: Victor Burnouts

Colin,
There is no real effective way to do that. In 2003, the "ice" produced incredible sparks so we dragged a tail (the outer shield of a braided coax without insulation or center conductor) and that helped a little when the robot contacted the ramp. (made of copper plated steel) This method was determined to be legal by FIRST for that year only.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
  #56   Spotlight this post!  
Unread 09-12-2005, 15:59
lupjohn's Avatar
lupjohn lupjohn is offline
Registered User
AKA: Larry Upjohn
FRC #0692 (FemBots)
Team Role: Mentor
 
Join Date: Oct 2004
Rookie Year: 2002
Location: Sacramento, CA
Posts: 31
lupjohn is an unknown quantity at this point
Re: Victor load testing

Quote:
Originally Posted by WizardOfAz
This sure provoked some interesting suggestions! My favorite is the salt water swimming pool...

At lunch I went over to the electronics store and bought 10 3.6 ohm 25 watt resistors. We'll wire them in parallel, in two banks of 5 each, so we can test with either (approx) 450 or 225 watts load at full power (12.8 volts). This should give a max current through the Victor of about 36A, a reasonably safe 10% below max rating for it. These are rectangular concrete resistors, so we can cool them with a slab of steel laid across all of them that will have pretty good surface contact, and keep the full power tests reasonably brief, since at max the resistors will be dissipating about 46 watts of heat each, substantially over their 25 watt rated limit. The steel will also protect from the shrapnel if they blow up....

Thanks again for the ideas.

Bill
Bill;
Check out this link.
http://www.harborfreight.com/cpi/cta...emnumber=90636

This is an auto battery/charging system analyzer but cheap enough to modify for your purposes. You might even rescale the meter and get some sort of go/nogo test rig setup. Enjoy, Larry U.
  #57   Spotlight this post!  
Unread 10-12-2005, 15:24
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: 10,798
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: Victor load testing

Quote:
Originally Posted by lupjohn
Bill;
Check out this link.
http://www.harborfreight.com/cpi/cta...emnumber=90636

This is an auto battery/charging system analyzer but cheap enough to modify for your purposes. You might even rescale the meter and get some sort of go/nogo test rig setup. Enjoy, Larry U.
Remember the old adage about " if it looks to good to be true it is"? I think that is the case here.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
  #58   Spotlight this post!  
Unread 10-12-2005, 16:00
Joe Johnson's Avatar Unsung FIRST Hero
Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Raynham, MA
Posts: 2,648
Joe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond repute
Re: Victor load testing

Quote:
Originally Posted by Al Skierkiewicz
Remember the old adage about " if it looks to good to be true it is"? I think that is the case here.
Chief Delphi has (or had a few years ago at least) one of these rigged with a standard FIRST battery connector. It is (was ) a good way to know if the battery was charged - it is not perfect but it is a lot better than going by unloaded voltage which is the way many folks try to tell if a battery is fully charged.

But to the matter at hand, they have a coil that literally glows like a toaster when enough current is passed through. I don't know what the current that makes the thing glow is, I but am pretty sure it is above the 36A you are trying to test. I would think that you could calibrate the PWM value of your Victor tester to give you the 36Amp test current.

Anyway, in my opinion, it possible that this tester could dispate the amount of electrical power you are looking for especially if you are only looking for short time periods. A toaster is typcially 1000W or more, you are talking about 36A at perhaps 12V, clearly under 500W.

For $20, it seems to be worth at least a shot.

For what it's worth.

Joe J.
__________________
Joseph M. Johnson, Ph.D., P.E.
Mentor
Team #88, TJ2

Last edited by Joe Johnson : 10-12-2005 at 16:06.
  #59   Spotlight this post!  
Unread 18-02-2007, 23:38
NeilS NeilS is offline
Registered User
FRC #0811
 
Join Date: Jan 2007
Location: NH
Posts: 2
NeilS is an unknown quantity at this point
Re: Victor Burnouts

We have fried 3 Victors on one motor this year, and the 40 AMP fuse has not tripped... I suspect it is because a short on the motor, because everything else seems fine.

There is another idea.
  #60   Spotlight this post!  
Unread 19-02-2007, 07:38
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: 10,798
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: Victor Burnouts

Neil,
It is clearly a problem with that motor if there are other motors on your robot with similar transmissions. It is entirely possible for there to be a mechanical problem that is causing the failures. However, do not rule out the possibilty that the mounting position for that Victor allows it to gather dust thrown up by the motor. I have encountered teams that had positioned the Victor directly in line with the main gear in their transmission which threw little bits of metal into the Victor every time they ran the robot.
__________________
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


All times are GMT -5. The time now is 03:40.

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