OCCRA
Go to Post Many of us are engineers who value precision and accuracy in communication. Words mean things. - Alan Anderson [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

 
Reply
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 01-12-2018, 08:13 AM
beanieweenie beanieweenie is offline
Registered User
FRC #5987
 
Join Date: Nov 2016
Location: Israel
Posts: 19
beanieweenie has a spectacular aura aboutbeanieweenie has a spectacular aura about
Frequently burning VRM's

Our team has 3 out of 4 not working VRM's.
We're trying to find the cause of this, what could be the reason for the burnt/not working VRM's?
Reply With Quote
  #2   Spotlight this post!  
Unread 01-12-2018, 08:16 AM
MrForbes's Avatar
MrForbes MrForbes is offline
Registered User
AKA: Jim
FRC #1726 (N.E.R.D.S.)
Team Role: Mentor
 
Join Date: Feb 2006
Rookie Year: 2006
Location: Sierra Vista AZ
Posts: 6,401
MrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond repute
Re: Frequently burning VRM's

Maybe you are connecting things to the, that draw too much current?

Let us know exactly how you are using the VRM. What do you connect to it?
Reply With Quote
  #3   Spotlight this post!  
Unread 01-12-2018, 08:24 AM
JamesCH95's Avatar
JamesCH95 JamesCH95 is offline
Hardcore Dork
AKA: JCH
FRC #0095 (The Grasshoppers)
Team Role: Engineer
 
Join Date: Dec 2004
Rookie Year: 2001
Location: Enfield, NH
Posts: 2,580
JamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond repute
Re: Frequently burning VRM's

How have you determined that they're broken?
What was connected when they allegedly died?
What wiring practices are you employing to stop short circuits at the connectors?
What was happening with the robot's electrical system when they died?
Do you disconnect your main breaker before changing batteries?

Y'all got any more of them details?
__________________
Theory is a nice place, I'd like to go there one day, I hear everything works there.

Maturity is knowing you were an idiot, common sense is trying to not be an idiot, wisdom is knowing that you will still be an idiot.
Reply With Quote
  #4   Spotlight this post!  
Unread 01-12-2018, 08:50 AM
FrankJ's Avatar
FrankJ FrankJ is offline
Robot Mentor
FRC #2974 (WALT)
Team Role: Mentor
 
Join Date: Feb 2011
Rookie Year: 2009
Location: Marietta GA
Posts: 2,473
FrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond reputeFrankJ has a reputation beyond repute
Re: Frequently burning VRM's

While not disconnecting the battery SB connector under load is certainly a good idea and generally a best practice, I am not sure if it any less electrically Noisey than the breaker switch. It not like there is a lot of load on it.

We have found the VRM very reliable. But we are very careful with the electrical. With the little information given, I would start with looking for shorts and making sure you are not trying to draw too much current. Talking directly to CTRE customer service would be useful too.
__________________
If you don't know what you should hook up then you should read a data sheet
Reply With Quote
  #5   Spotlight this post!  
Unread 01-12-2018, 12:58 PM
philso philso is offline
Mentor
no team
 
Join Date: Jan 2011
Rookie Year: 2009
Location: Houston, Tx
Posts: 1,638
philso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond repute
Re: Frequently burning VRM's

Have they been connected with the input voltage reversed? Have the outputs been connected to the 12 V from the PDP?

My understanding is that the VRM has two switching regulators in it, one to make the stable 12 V output and one to make the 5 V output. These circuits typically have very good self-protection features and usually can survive a short circuit.

If 3 in a row have died, check the input wiring from the PDP, both ends.
Reply With Quote
  #6   Spotlight this post!  
Unread 01-12-2018, 01:33 PM
bobbysq bobbysq is online now
Registered User
FRC #4646 (Team ASAP)
Team Role: Alumni
 
Join Date: Apr 2016
Rookie Year: 2015
Location: Des Moines, IA
Posts: 914
bobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond reputebobbysq has a reputation beyond repute
Re: Frequently burning VRM's

Quote:
Originally Posted by philso View Post
These circuits typically have very good self-protection features and usually can survive a short circuit.
I can concur from experience. We accidentally had a pinched wire coming off of the VRM in 2016 and it was able to take it perfectly.
Reply With Quote
  #7   Spotlight this post!  
Unread 01-12-2018, 10:03 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 9,126
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Frequently burning VRM's

Quote:
Originally Posted by beanieweenie View Post
Our team has 3 out of 4 not working VRM's.
We're trying to find the cause of this, what could be the reason for the burnt/not working VRM's?
You got a bunch of responses.

We'd like to hear back from you.


Reply With Quote
  #8   Spotlight this post!  
Unread 01-13-2018, 10:26 AM
beanieweenie beanieweenie is offline
Registered User
FRC #5987
 
Join Date: Nov 2016
Location: Israel
Posts: 19
beanieweenie has a spectacular aura aboutbeanieweenie has a spectacular aura about
Re: Frequently burning VRM's

We're connecting only the radio to the VRM, nothing else
Reply With Quote
  #9   Spotlight this post!  
Unread 01-13-2018, 11:26 AM
philso philso is offline
Mentor
no team
 
Join Date: Jan 2011
Rookie Year: 2009
Location: Houston, Tx
Posts: 1,638
philso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond repute
Re: Frequently burning VRM's

Quote:
Originally Posted by beanieweenie View Post
We're connecting only the radio to the VRM, nothing else
So does it work now?

It is most likely that an incorrect connection was made to the 12 V supply on the PDP. Unfortunately, if what you have now is working, the evidence of an incorrect connection will have been destroyed.

In the future, have a second, detailed oriented person check EVERY wire against the wiring diagram before applying power.
Reply With Quote
  #10   Spotlight this post!  
Unread 01-13-2018, 12:44 PM
beanieweenie beanieweenie is offline
Registered User
FRC #5987
 
Join Date: Nov 2016
Location: Israel
Posts: 19
beanieweenie has a spectacular aura aboutbeanieweenie has a spectacular aura about
Re: Frequently burning VRM's

We checked the connections, they are okay, the burnt VRM's are not working no matter what, our other VRM is working fine so we assume that they probably drew too much current.
Reply With Quote
  #11   Spotlight this post!  
Unread 01-13-2018, 08:25 PM
philso philso is offline
Mentor
no team
 
Join Date: Jan 2011
Rookie Year: 2009
Location: Houston, Tx
Posts: 1,638
philso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond reputephilso has a reputation beyond repute
Re: Frequently burning VRM's

Quote:
Originally Posted by beanieweenie View Post
We checked the connections, they are okay, the burnt VRM's are not working no matter what, our other VRM is working fine so we assume that they probably drew too much current.
As stated before, all of the chips used in designs like this are designed to protect the circuit from output short circuits without sustaining permanent damage. All the ones I have worked with could withstand having a constant short applied across the output and will start working properly once the short is removed. It is virtually impossible for a chip manufacturer to sell one that cannot do this now.

It is more likely that the dead ones were connected with the input wires reversed or the 12V input was connected to the outputs. That is why I suggested that in the future, have a second, detailed oriented person check EVERY wire against the wiring diagram before applying power. This is standard operating procedure in a manufacturing environment.

For a definitive answer, you can contact CTRE and ask if they will perform a failure analysis on the dead ones if you send them back to them. Since they are the developers of this product, they are likely to have seen examples of many different failure modes. They might even be able to repair them for a reasonable fee . Sorry, I just noticed that you are in Israel so the cost of the shipping might make it impractical to ship the dead ones around.

Last edited by philso : 01-13-2018 at 08:27 PM.
Reply With Quote
  #12   Spotlight this post!  
Unread 01-15-2018, 08:11 AM
beanieweenie beanieweenie is offline
Registered User
FRC #5987
 
Join Date: Nov 2016
Location: Israel
Posts: 19
beanieweenie has a spectacular aura aboutbeanieweenie has a spectacular aura about
Re: Frequently burning VRM's

We'll make sure to check the connections before applying power.
Thanks everyone!
Reply With Quote
  #13   Spotlight this post!  
Unread 01-15-2018, 08:20 AM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 9,126
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Frequently burning VRM's

Quote:
Originally Posted by beanieweenie View Post
We'll make sure to check the connections before applying power.
Thanks everyone!
Please save those burned-out VRMs in a safe place, and bring them to the US if you guys go to champs.

Give them to CTRE for autopsy.

You really should find out what caused their death, so you can learn what not to do.


Reply With Quote
  #14   Spotlight this post!  
Unread 01-15-2018, 08:31 AM
beanieweenie beanieweenie is offline
Registered User
FRC #5987
 
Join Date: Nov 2016
Location: Israel
Posts: 19
beanieweenie has a spectacular aura aboutbeanieweenie has a spectacular aura about
Re: Frequently burning VRM's

We'll make sure to do that, thank you!
Reply With Quote
  #15   Spotlight this post!  
Unread 01-20-2018, 10:52 AM
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
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: 11,110
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: Frequently burning VRM's

beanie,
What you describe is generally related to the wiring going to the radio. Be sure that everything is fully insulated and the wiring is not pinched under a mechanical part of the robot. The wire that is supplied with the radio has very thin insulation and it is common to be pinched together under a mechanical part. The best method to check the cable is to squeeze the wire between your fingers and slide them from one end to the other. Any part of the cable that feels rough or has indents was likely damaged at one point. Replace when you can, it will fail you when you need the most.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Knowledge is power. Power UP!
Reply With Quote
Reply


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 12:49 PM.

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


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi