Searching \ for '[ELEC]: PCB for High Current (help)' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/pcbs.htm?key=pcb
Search entire site for: ': PCB for High Current (help)'.

Exact match. Not showing close matches.
PICList Thread
'[ELEC]: PCB for High Current (help)'
2003\03\07@163308 by Donovan Parks

flavicon
face
Hello,

I am designing a PCB for a motor controller I have developed for a small underwater vehicle being developed at the University of Victoria (http://www.engr.uvic.ca/~auv).  I have a few concerns about putting up to 20A through a PCB trace though.  By searching the web I have been able to find a nice program by John Brown (http://hampcb.com/downloads.html) that calculates the maximum current carrying capacity of a copper trace based on the acceptable temperature raise above ambient, trace width, and copper thickness.  This is exactly what I am looking for except I have been unable to determine what an acceptable temperature raise above ambient is.  At what temperature will the copper trace start to peal off the board?

This program indicates that with a trace width of 300 mils, an allowable temperature raise of 50 degree C, and 1 Oz copper plating I can handle 21A - does this sound reasonable?

In the same vein, can I put 20A though a throughhole with a pin (i.e. through the leg of my MOSFET from on side of the board to the other) without taking special precautions? I realize I can't put 20A through a simple via, but am not sure if I can do it with a throughole with a pin in it.

Sorry for all the questions and obvious lack of knowledge, but this is only my second PCB and the first that has carried any serious current.

Thanks,
Donovan

--
http://www.piclist.com hint: To leave the PICList
spam_OUTpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu>

2003\03\07@172302 by Lawrence Lile

flavicon
face
A standard trick that us manufatrurers use is to solder a thick bare
copper wire to the board.  Get the circular mils of copper up to equal a
similar bare wire and you'll be safe.  Look up wire current carrying
capacity in an NEC handbook or on a wire mfr's site.  If this is a one-off
or a short production run that won't be a problem.

Yes you can carry plenty of current through a throughhole pin with a leg
in it, I wouldn't worry about it if the pin itself can handle the current.


You can also go to 2 oz copper, for greater current carrying ability.

I handle 15 amps and 120V all the time on PCB traces in commercial
products, so as long as you stay within the safe temperature rise area you
should be OK.

Each PCB material has a different maximum temperature rating, either rated
in absolute temperature or temperature rise above ambient.  I don't have
this info handy, but memory says FR4 is rated about 130C absolute.  If you
keep your temperature rise under 80C (55 rise above ambient) you will be
plenty safe.




-- Lawrence Lile





Donovan Parks <.....dparksKILLspamspam@spam@UVIC.CA>
Sent by: pic microcontroller discussion list <PICLISTspamKILLspamMITVMA.MIT.EDU>
03/07/2003 02:52 PM
Please respond to pic microcontroller discussion list


       To:     .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
       cc:
       Subject:        [ELEC]: PCB for High Current (help)


Hello,

I am designing a PCB for a motor controller I have developed for a small
underwater vehicle being developed at the University of Victoria
(http://www.engr.uvic.ca/~auv).  I have a few concerns about putting up to 20A
through a PCB trace though.  By searching the web I have been able to find
a nice program by John Brown (http://hampcb.com/downloads.html) that calculates the maximum current carrying capacity of a copper trace
based on the acceptable temperature raise above ambient, trace width, and
copper thickness.  This is exactly what I am looking for except I have
been unable to determine what an acceptable temperature raise above
ambient is.  At what temperature will the copper trace start to peal off
the board?

This program indicates that with a trace width of 300 mils, an allowable
temperature raise of 50 degree C, and 1 Oz copper plating I can handle 21A
- does this sound reasonable?

In the same vein, can I put 20A though a throughhole with a pin (i.e.
through the leg of my MOSFET from on side of the board to the other)
without taking special precautions? I realize I can't put 20A through a
simple via, but am not sure if I can do it with a throughole with a pin in
it.

Sorry for all the questions and obvious lack of knowledge, but this is
only my second PCB and the first that has carried any serious current.

Thanks,
Donovan

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspam_OUTspamTakeThisOuTmitvma.mit.edu



--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamspam_OUTmitvma.mit.edu>

2003\03\07@180323 by Glen Holmes

flavicon
face
Hi Donovan;

I checked an IPC chart and it showed the maximum rated temp for FR-4 to be 125 degree C.  If the PCB is in a 20 degree C environment then you are allowed a 105 degree C temperature rise form the current.

I'm not sure if a pin is going to be able to carry 20A.  As already suggested, you could look in the Canadian equivalent of the National Electric Code to determine the "ampacity" of a conductor the same size as your pin. Remember to consider the temperature rise from ambient.

glen
{Original Message removed}

2003\03\07@183003 by Chris Loiacono

flavicon
face
I have used this calculator before. prior to that I had a hand-written list
that was compiled from experience. Now I use both plus some common sense.

My 2 cents:
If you have the time & $$, use 2 oz Cu or more.
I also use the piggyback wire to trace trick - have done so for close to 20
yrs.
Keep the high current runs as short as possible and in open areas as much as
is possible. If they are beneath a transformer or some such place, they will
have more of a tendency to cook.

Also this is a good place to do copper pours in your CAD layout - even if
you still have some narrow points in the run the extra copper makes a nice
heat sink which helps somewhat.

Another good idea is to save enough room on the board to copy one layer to
the other, effectively doubling the ampacity. A few extra vias evenly spaced
may make you feel better, but I don't kow that they actually do much - can't
hurt though. I regularly do 35 to 40A on all commercial board materials
without any probles seen in many years - just by these simple means - in
fact just finished one that is now out for fab that has a pair of 35A paths
on it to & from an alternistor. - was 'poured' in Eagle, mirrored on both
sides and will be wired with some bare copper Monday!


Don't sweat it - it was wise to look inot this, but 20 Amps is very do-able.

Chris

{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestKILLspamspammitvma.mit.edu>

2003\03\07@214835 by William Chops Westfield

face picon face
>> You can also go to 2 oz copper, for greater current carrying ability.

Or higher.  I have some surplus PCB material that has 3oz copper on one
side and 1oz on the other side (I should have read the label more
carefully before buying - that's NOT what I wanted...)

BillW

--
http://www.piclist.com hint: To leave the PICList
KILLspampiclist-unsubscribe-requestKILLspamspammitvma.mit.edu>

2003\03\08@023847 by Roman Black

flavicon
face
Donovan Parks wrote:

> In the same vein, can I put 20A though a throughhole with a pin (i.e. through the leg of my MOSFET from on side of the board to the other) without taking special precautions? I realize I can't put 20A through a simple via, but am not sure if I can do it with a throughole with a pin in it.


For reliability it will really be worth using
a plated through hole board, you get 4x the solder
contact to the pin and much better protection
from thermal expansion etc. If you must use single
sided PCB, run 10 mm of leg through the board, bend
it flat and solder it flat across 8mm of the track.

I suspect this will be in a small *sealed* container,
ambient is going to be hot. You really want to
keep temp rise as low as possible. If you can't
use a thicker track why not leave the solder mask
off that track so when it's tinned it will carry
a lot more current, and you can add a decent bead
of solder to the top giving a very thick trace.
This is common in microwave oven PCBs and saves
the hassle of soldering extra wires on top.

Solder gets soft as it gets over 100' and repeated
thermal expansion and soft solder caused many of
the TV faults i've fixed over the years. I've
always had a thermometer on my workbench and any
component leg running over 60'C TOTAL TEMP will
eventually fail and dry-joint often within a year
or two, with a plated through hole you can risk
70'C. I wouldn't even consider running a soldered
component leg at >80'C, especially in a sealed
container that will be annoying to repair. :o)
-Roman

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\03\08@183421 by Richard Graziano

picon face
The length of the conductor is also a factor.  If you look at a 50 amp
Motorola Bipolar Power transistor, you will be surprised to see that 50 amps
can flow through the emitter pin.  A wire conductor of the same cross
section of equivalent cross section would be unable to carry that amount of
current.  The combination of connector ampacity, the pin in contact with the
connector are certainly factors.  However, there is a very short distance
comprised only of pin conductor.

Hi current on PCB traces over any significant distance should be shunted
with a shorting bar specifically designed for that purpose, or a solid
copper wire.  The copper wire could be preformed and soldered to the trace
thru-holes.

Good luck
Rich
{Original Message removed}

2003\03\11@042702 by Pang

flavicon
face
Hi Chris,

Can I know, when the copper pour is done, do you do it for the GND or the
Vcc or the track that is carrying the huge current? I have done an
automotive project that has an onboard relay. The relay carries huge
current, ~40A and we have practically done all that is mention. ( short
track, track on both side of the pcb and increase the width). I am
wondering, for the sake of long term usage, is it advisable that we just use
those external relay or can the board withstand the current and still
function well?

Thanks.

Pang



{Original Message removed}

2003\03\11@094907 by Lawrence Lile

flavicon
face
Many manufacturers make relays with a high current terminal on TOP of the
relay, with a quick-connect terminal.  These might be more appropriate for
what you are doing.  Omron, Aromat/Nais, and a lot of others have them.



-- Lawrence Lile





Pang <RemoveMEklpangTakeThisOuTspamAICM.COM.MY>
Sent by: pic microcontroller discussion list <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
03/11/2003 03:20 AM
Please respond to pic microcontroller discussion list


       To:     TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
       cc:
       Subject:        Re: [ELEC]: PCB for High Current (help)


Hi Chris,

Can I know, when the copper pour is done, do you do it for the GND or the
Vcc or the track that is carrying the huge current? I have done an
automotive project that has an onboard relay. The relay carries huge
current, ~40A and we have practically done all that is mention. ( short
track, track on both side of the pcb and increase the width). I am
wondering, for the sake of long term usage, is it advisable that we just
use
those external relay or can the board withstand the current and still
function well?

Thanks.

Pang



{Original Message removed}

More... (looser matching)
- Last day of these posts
- In 2003 , 2004 only
- Today
- New search...