Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.

Richard

On Sun, 11 Jan 2004 19:44:19 +0800, Richard Hosking
wrote:

Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.

Richard

Rick,
one way for reverse protection is to include a bridge recifier in the
rigs power line ( internally fitted ), but this causes a drop in
available volts.

I prefer a diode into a relay coil, with the relay contacts enabling
the power when the relay coil is correctly polarised and powered (
also internally fitted ).

This enables full volts to the rig and also gives reverse protection,
however this is at the cost of further ( and some may say excessive )
drain of the power source.
Over voltage should be by fuse and a crowbar circuit. Do a search on
crowbar for details.

The diode + relay circuit should be obvious to you, I use a 9v relay
coil with a 1N4001 in the activation side and a DPDT contact,in
parallel, to switch the power. For the power you are talking about a
14pin DIL relay should be adequate.

HTH, Mike W, G8NXD qthr

On Sun, 11 Jan 2004 19:44:19 +0800, Richard Hosking
wrote:

Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.

Richard

Rick,
one way for reverse protection is to include a bridge recifier in the
rigs power line ( internally fitted ), but this causes a drop in
available volts.

I prefer a diode into a relay coil, with the relay contacts enabling
the power when the relay coil is correctly polarised and powered (
also internally fitted ).

This enables full volts to the rig and also gives reverse protection,
however this is at the cost of further ( and some may say excessive )
drain of the power source.
Over voltage should be by fuse and a crowbar circuit. Do a search on
crowbar for details.

The diode + relay circuit should be obvious to you, I use a 9v relay
coil with a 1N4001 in the activation side and a DPDT contact,in
parallel, to switch the power. For the power you are talking about a
14pin DIL relay should be adequate.

HTH, Mike W, G8NXD qthr

Mike W wrote:
Over voltage should be by fuse and a crowbar circuit. Do a search on
crowbar for details.

If you already have a fuse & crowbar circuit for overvoltage, wouldn't
the easy way to handle reverse polarity be a diode hooked in the
(normally) non-conducting direction across the output?
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Mike W wrote:
Over voltage should be by fuse and a crowbar circuit. Do a search on
crowbar for details.

If you already have a fuse & crowbar circuit for overvoltage, wouldn't
the easy way to handle reverse polarity be a diode hooked in the
(normally) non-conducting direction across the output?
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

I'm not understanding something here. You want to design a power supply that
protects against reverse voltage and overvoltage. OK. Is this power supply a
battery or are you actually building a power supply that runs from the wall
outlet?

The requirements are quite different, depending on what you are trying to
achieve.

Jim



Richard Hosking
shared these priceless pearls of wisdom:

-Dear all
-I want to design a power supply for a low power rig with protection for
-reverse and overvoltage.


Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

I'm not understanding something here. You want to design a power supply that
protects against reverse voltage and overvoltage. OK. Is this power supply a
battery or are you actually building a power supply that runs from the wall
outlet?

The requirements are quite different, depending on what you are trying to
achieve.

Jim



Richard Hosking
shared these priceless pearls of wisdom:

-Dear all
-I want to design a power supply for a low power rig with protection for
-reverse and overvoltage.


Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

In article ,
says...

Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.

Power Schottky diodes are available that have a forward voltage
drop of 0.3 or less. More expensive, yes, but they really do work.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

In article ,
says...

Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.

Power Schottky diodes are available that have a forward voltage
drop of 0.3 or less. More expensive, yes, but they really do work.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

On Sun, 11 Jan 2004 14:05:21 GMT, (Mike W)
wrote:



The diode + relay circuit should be obvious to you, I use a 9v relay
coil with a 1N4001 in the activation side and a DPDT contact,in
parallel, to switch the power. For the power you are talking about a
14pin DIL relay should be adequate.

HTH, Mike W, G8NXD qthr

I'd like to call it "the PYE method" since it is generally applied in
those Westminster, Vanguard and Cambridge sets, while other
manufacturers only use a diode. I've copied it for the larger sets
which are often used in different places. The application of relay has
the advantage that nothing happens if you use the wrong polarity -
unless you have shortcircuit between two chassises, then you should
apply a two-pole relay.
Make sure that the relay stays operated under different operation,
check that the relay operates with 9V. Remember to put a diode or
other spark suppression across the coil, too.

73
LA8AK, http://home.online.no/~la8ak/c.htm
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