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

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

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
--
Amount of SPAM is so large that MailWasher must delete 99% of the incoming mails
Cannot check every email manually. Please use intelligent title for email.
Mails without titles or using just "hi" is deleted

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

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
--
Amount of SPAM is so large that MailWasher must delete 99% of the incoming mails
Cannot check every email manually. Please use intelligent title for email.
Mails without titles or using just "hi" is deleted

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

Jim
The rig will be powered from a 12V source eg battery/AC wallwart
/whatever. However, internally the rig needs various voltages, including
1.8V for logic and -12V. I want to ptotect against inadvertent
overvoltage or reverse voltage. I want it to be as efficient as
possible, so I dont want to use a linear regulator. SMPS seems the
obvious choice. I may well shield the PSU section, and isolate the
ground etc to reduce noise. I was seeking advice from the experts here
as to whether the idea is feasible and whether there is a redaymade
solution.

Richard

Jim Weir wrote:
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

This may need re-stating. The reverse polarity protection goes IN THE
RADIO, not the power supply. Right fellas?
--
Steve N, K,9;d, c. i My email has no u's.


??? Fort Hose... ??? Cute also:

When the clock gets near 12:00 I stick my head in teh co-workers office &
say
Djeet Jet? If the response is no, then;"Tsqueet!"



"Jim Weir" wrote in message
...

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

Jim
The rig will be powered from a 12V source eg battery/AC wallwart
/whatever. However, internally the rig needs various voltages, including
1.8V for logic and -12V. I want to ptotect against inadvertent
overvoltage or reverse voltage. I want it to be as efficient as
possible, so I dont want to use a linear regulator. SMPS seems the
obvious choice. I may well shield the PSU section, and isolate the
ground etc to reduce noise. I was seeking advice from the experts here
as to whether the idea is feasible and whether there is a redaymade
solution.

Richard

Jim Weir wrote:
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