Date: Wed, 17 Nov 2010 09:58:36

Author: Keith Warren

Subject: Re: 20A DC power supply ideas

Post:

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I second Jerry here. Based on his recommendation we purchased the same =
supply earlier this year. We then mounted a .33 ohm, 40A current =
limiting resistor to the supply housing. The resistor cost about \$70 =
from Post Glover. The setup works great.

=20

-Keith

NCSU

=20

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf Of Zani, Gerald
Sent: Wednesday, November 17, 2010 8:41 AM
To: tap-l
Subject: Re: [tap-l] 20A DC power supply ideas

=20

I use a wonderful 35 Amp! low voltage variable 0 - 14 VDC power supply =
designed for mobile Ham Radio hobby use from MFJ Enterprises.

If I remember correctly I originally paid about ~\$130 for it about ~12 =
years ago so time has proven that it works well.

=20

It is the MFJ model 4035MV:

=20

http://www.mfjenterprises.com/Product.php?productid=3DMFJ-4035MV

=20

MFJ Enterprises

Starkville, LA 39759

http://www.mfjenterprises.com/=20

=20

I bought a 1/4 Ohm, ~1000 Watt resistor to serve as a series ballast. =
When I have a short circuit load I use the ballast resistor so the power =
supply can handle a continuous short circuit load without tripping the =
internal crowbar protection circuit. Been using it for 12 years to =
create magnetic fields for various wire lengths and geometries. Because =
it is variable from 0 - 14 VDC I can adjust the current as desired to =
maximize the magnetic field strength but prevent it from over heating =
the wire.

=20

- JZ

=20

2010/11/17 Simcha Segev

Chuck and all,

Car battery chargers may supply up to 20A but usually the DC is with a =
great
ripple. As the current is higher, the ripple and noise are huge and this
become more AC then DC.

Bill, the HP 6264B costs 10 times more then you wrote i.e 1200\$ and up. =
If
you have a better price proposal, please inform us.

Thanks, Simcha

Simcha Segev
Physics Demonstration Lab
School of Physics and Astronomy
Tel Aviv University, Ramat aviv, Israel
Tel. 972-3-6408077 Fax. 972-3-6429306
E-mail: simcha@post.tau.ac.il
Web site : http://www.tau.ac.il/~simcha

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=D7=9E=D7=90=D7=AA: tap-l-owner@lists.ncsu.edu =
[mailto:tap-l-owner@lists.ncsu.edu] =D7=91=D7=A9=D7=9D
chuck britton
=D7=A0=D7=A9=D7=9C=D7=97: =D7=93 17 =D7=A0=D7=95=D7=91=D7=9E=D7=91=D7=A8 =
2010 00:24
=D7=90=D7=9C: tap-l@lists.ncsu.edu
=D7=A0=D7=95=D7=A9=D7=90: Re: [tap-l] 20A DC power supply ideas

Car battery chargers work fine.
Rugged and inexpensive.

At 11:58 AM -0800 11/16/10, John Welch wrote:
>Hey all - I'm looking for recommendations for a relatively cheap way
>to get a 20A DC power supply. I don't really care about the voltage
>rating, since I'll just be shorting it most of the time to create
>magnetic fields around wires. So it has to be something that is
>regulated enough that it can be shorted without blowing fuses. It
>doesn't have to be 20A exactly, but in that ball park. Do car
>battery charges work for this?

=20

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I second =
Jerry here.=C2=A0 Based on his recommendation we purchased the same =
supply earlier this year.=C2=A0 We then mounted a .33 ohm, 40A current =
limiting resistor to the supply housing.=C2=A0 The resistor cost about =
\$70 from Post Glover.=C2=A0 The setup works =
great. =
-Keith=
NCSU =
From:=
=
tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf Of Zani, GeraldSent: Wednesday, November 17, 2010 =
8:41 AMTo: tap-lSubject: Re: [tap-l] 20A DC power =
supply ideas I use a =
wonderful 35 Amp! low voltage variable 0 - 14 VDC power supply =
designed for mobile Ham Radio hobby use from MFJ =
Enterprises.If I remember =
correctly I originally paid about ~\$130 for it about ~12 years ago so =
time has proven that it works well. It is the MFJ model =
4035MV: http://www.mfjenterprises.com/Product.php?productid=3DM=
FJ-4035MV MFJ EnterprisesStarkville, LA 39759http://www.mfjenterprises.com/ =
I bought a 1/4 Ohm, ~1000 Watt resistor to serve as a =
series ballast. When I have a short circuit load I use the ballast =
resistor so the power supply can handle a continuous short circuit load =
without tripping the internal crowbar protection circuit. Been =
using it for 12 years to create magnetic fields for various wire =
lengths and geometries. Because it is variable from 0 - 14 VDC =
I can adjust the current as desired to maximize the magnetic field =
strength but prevent it from over heating the =
wire. - =
JZ 2010/11/17 Simcha Segev Chuck and =
all,Car battery chargers may supply up to 20A but usually the DC =
is with a greatripple. As the current is higher, the ripple and =
noise are huge and thisbecome more AC then DC.Bill, the HP =
6264B costs 10 times more then you wrote i.e 1200\$ and up. Ifyou =
have a better price proposal, please inform us.Thanks, =
SimchaSimcha SegevPhysics Demonstration =
LabSchool of Physics and =
AstronomyTel Aviv University, Ramat aviv, =
IsraelTel. 972-3-6408077 Fax. 972-3-6429306E-mail: =
simcha@post.tau.ac.ilWeb site : http://www.tau.ac.il/~simcha-----=D7=94=D7=95=D7=93=D7=A2=D7=94 =
=D7=9E=D7=A7=D7=95=D7=A8=D7=99=D7=AA-----=D7=9E=D7=90=D7=AA: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] =
=D7=91=D7=A9=D7=9Dchuck britton=D7=A0=D7=A9=D7=9C=D7=97: =D7=93 =
17 =D7=A0=D7=95=D7=91=D7=9E=D7=91=D7=A8 2010 00:24=D7=90=D7=9C: tap-l@lists.ncsu.edu=D7=A0=D7=95=D7=A9=D7=90: =
Re: [tap-l] 20A DC power supply ideasCar battery chargers work =
fine.Rugged and inexpensive.At 11:58 AM -0800 11/16/10, =
John Welch wrote:>Hey all - I'm looking for recommendations for a =
relatively cheap way>to get a 20A DC power supply. I don't really =
care about the voltage>rating, since I'll just be shorting it =
most of the time to create>magnetic fields around wires. So it =
has to be something that is>regulated enough that it can be =
shorted without blowing fuses. It>doesn't have to be 20A exactly, =
but in that ball park. Do car>battery charges work for =
this?
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From tap-l-owner@lists.ncsu.edu Wed Nov 17 09:59:26 2010