I want to run two computer power supplies, and have 1 turn on by a relay
when the first one is turned on.
The power supplies are 96 W and 250 W. I understand that a 12V DC always on
relay is what I need, but I am not sure what amps it needs to be rated at.

The way it will work is this. I have a 96 Watt power supply that is turned
on, and I want it to trigger an ATX 250 W power supply to come on as well.
The relay will be powered by the 96 watt power supply, and the switch in the
relay will connect the green and black wires of the ATX power supply so it
will be on. If anyone has any information on what I should be looking for, I
would appreciate it.

Regards,
KDawg

On Thu, 21 Aug 2003 18:44:12 GMT, "KDawg"
wrote:

I want to run two computer power supplies, and have 1 turn on by a relay
when the first one is turned on.
The power supplies are 96 W and 250 W. I understand that a 12V DC always on
relay is what I need, but I am not sure what amps it needs to be rated at.

By always on you mean a duty cycle of 100%? (that would be correct)

The way it will work is this. I have a 96 Watt power supply that is turned
on, and I want it to trigger an ATX 250 W power supply to come on as well.
The relay will be powered by the 96 watt power supply, and the switch in the
relay will connect the green and black wires of the ATX power supply so it
will be on. If anyone has any information on what I should be looking for, I
would appreciate it.

Regards,
KDawg

Your choices are to power the relay from a 12 volt voltage source in
the 96 watt supply, to keep the voltage of the relay low and make it
safer, or just run a 120 volt relay from the same switch that powers
the 96 watt supply (in which case why not just plug both supplies into
the same power strip, and leave the black and green wires connected at
all times?) Wouldn't work if the black and green is the reset line on
the ATX . . .

If you intend to sense the current through the 96 watt supply and turn
on the 250 every time the current exceeds a certain threshold - that
can be done but takes more explanation.

Your relay contacts need to be heavy enough to switch whatever current
the green and black wires of the ATX supply carry. I don't know that.
I assume they would be a logic level, in which case the current is
minuscule and the relay would need to be no more than a small reed
relay.

The relay you need is one that has a coil voltage for how you plan to
power it . . . . AC mains 120/240 VAC or a 12 DC or 5 DC volt source
from the 96W supply. (relay coils need to be AC types for AC
operation and DC for DC)

You need a "normally open" set of contacts on the relay. The contacts
stay open as long as the relay is de energized.

Never heard the term "always on" with respect to relays but it seems
to imply normally closed contacts - which isn't what you want. (the
ATX would come on when the 96W went off) Many relays have a contact
that can be wired either normally open or normally closed (single pole
double throw)


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Thanks for the info. I meant normally on as opposed to always on.
I have a 2 different relays in mind, both seem identical except 1 is .5 amp,
and the other is 20 amp.
What does the amp have to do with anything here ? Which one should I go with
?
THe ATX just needs a constant short between the green and black wire in
order to turn on and run. I don't think
either of these lines are used as major power supply lines. Just needs to be
connected thats all I know, thats what I want the relay to do, is keep the
connection, whenever the relay is getting power from another source
(96watt). As I have it now, I am using a paperclip to short the 2 wires, but
this requires me to use 2 switches to turn the system on, whereas I would
like to try accomplish this with 1 switch.

Also the 96 power supply is hooked up to a momentary push button to turn it
on. Once it is on, then I want the ATX power supply to kick in.

Regards,
KDawg
"default" wrote in message
...
On Thu, 21 Aug 2003 18:44:12 GMT, "KDawg"
wrote:

I want to run two computer power supplies, and have 1 turn on by a relay
when the first one is turned on.
The power supplies are 96 W and 250 W. I understand that a 12V DC always
on
relay is what I need, but I am not sure what amps it needs to be rated
at.

By always on you mean a duty cycle of 100%? (that would be correct)

The way it will work is this. I have a 96 Watt power supply that is
turned
on, and I want it to trigger an ATX 250 W power supply to come on as
well.
The relay will be powered by the 96 watt power supply, and the switch in
the
relay will connect the green and black wires of the ATX power supply so
it
will be on. If anyone has any information on what I should be looking
for, I
would appreciate it.

Regards,
KDawg

Your choices are to power the relay from a 12 volt voltage source in
the 96 watt supply, to keep the voltage of the relay low and make it
safer, or just run a 120 volt relay from the same switch that powers
the 96 watt supply (in which case why not just plug both supplies into
the same power strip, and leave the black and green wires connected at
all times?) Wouldn't work if the black and green is the reset line on
the ATX . . .

If you intend to sense the current through the 96 watt supply and turn
on the 250 every time the current exceeds a certain threshold - that
can be done but takes more explanation.

Your relay contacts need to be heavy enough to switch whatever current
the green and black wires of the ATX supply carry. I don't know that.
I assume they would be a logic level, in which case the current is
minuscule and the relay would need to be no more than a small reed
relay.

The relay you need is one that has a coil voltage for how you plan to
power it . . . . AC mains 120/240 VAC or a 12 DC or 5 DC volt source
from the 96W supply. (relay coils need to be AC types for AC
operation and DC for DC)

You need a "normally open" set of contacts on the relay. The contacts
stay open as long as the relay is de energized.

Never heard the term "always on" with respect to relays but it seems
to imply normally closed contacts - which isn't what you want. (the
ATX would come on when the 96W went off) Many relays have a contact
that can be wired either normally open or normally closed (single pole
double throw)


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On Thu, 21 Aug 2003 19:55:48 GMT, "KDawg"
wrote:

Thanks for the info. I meant normally on as opposed to always on.
I have a 2 different relays in mind, both seem identical except 1 is .5 amp,
and the other is 20 amp.
What does the amp have to do with anything here ? Which one should I go with
The amperage you are referring to is the current the contacts of the
relay are designed to handle. If you were switching on a water
heater, for instance, you'd need the 20 amp contacts, an automobile
starter motor you'd need 100 amps.

I suspect your black and green wire are very low current - a good
indicator is the thickness of the copper wire. If it is power supply
mains voltage the wire thickness would be around 1/16" or so, signal
wire would be much smaller.

Put a voltmeter across the grn and blk and measure the voltage; if it
is 120 AC you need to consider that and have at least a 5 amp contact
to be safe, if it is low DC the .5 amp contacts would be more than
enough.

You still need at least one set of contacts on the relay that are
"normally open" specified with the relay de energized (the convention
in such things). Normally on still implies normally closed (since a
closed switch is "on") that's not what you want. It is also less
common than normally open/off.

?
THe ATX just needs a constant short between the green and black wire in
order to turn on and run. I don't think
either of these lines are used as major power supply lines. Just needs to be
connected thats all I know, thats what I want the relay to do, is keep the
connection, whenever the relay is getting power from another source
(96watt). As I have it now, I am using a paperclip to short the 2 wires, but
this requires me to use 2 switches to turn the system on, whereas I would
like to try accomplish this with 1 switch.

Also the 96 power supply is hooked up to a momentary push button to turn it
on. Once it is on, then I want the ATX power supply to kick in.

Now it is making sense . . . the momentary switch is the reason for
this.

Regards,
KDawg
"default" wrote in message
.. .
On Thu, 21 Aug 2003 18:44:12 GMT, "KDawg"
wrote:

I want to run two computer power supplies, and have 1 turn on by a relay
when the first one is turned on.
The power supplies are 96 W and 250 W. I understand that a 12V DC always
on
relay is what I need, but I am not sure what amps it needs to be rated
at.

By always on you mean a duty cycle of 100%? (that would be correct)

The way it will work is this. I have a 96 Watt power supply that is
turned
on, and I want it to trigger an ATX 250 W power supply to come on as
well.
The relay will be powered by the 96 watt power supply, and the switch in
the
relay will connect the green and black wires of the ATX power supply so
it
will be on. If anyone has any information on what I should be looking
for, I
would appreciate it.

Regards,
KDawg

Your choices are to power the relay from a 12 volt voltage source in
the 96 watt supply, to keep the voltage of the relay low and make it
safer, or just run a 120 volt relay from the same switch that powers
the 96 watt supply (in which case why not just plug both supplies into
the same power strip, and leave the black and green wires connected at
all times?) Wouldn't work if the black and green is the reset line on
the ATX . . .

If you intend to sense the current through the 96 watt supply and turn
on the 250 every time the current exceeds a certain threshold - that
can be done but takes more explanation.

Your relay contacts need to be heavy enough to switch whatever current
the green and black wires of the ATX supply carry. I don't know that.
I assume they would be a logic level, in which case the current is
minuscule and the relay would need to be no more than a small reed
relay.

The relay you need is one that has a coil voltage for how you plan to
power it . . . . AC mains 120/240 VAC or a 12 DC or 5 DC volt source
from the 96W supply. (relay coils need to be AC types for AC
operation and DC for DC)

You need a "normally open" set of contacts on the relay. The contacts
stay open as long as the relay is de energized.

Never heard the term "always on" with respect to relays but it seems
to imply normally closed contacts - which isn't what you want. (the
ATX would come on when the 96W went off) Many relays have a contact
that can be wired either normally open or normally closed (single pole
double throw)


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On the relay contact ratings , you have to use a high enough rated
contact voltage to pervent arching ( which will likely trash the
driven comp PS ) and to prevent premature relay contact burnout .
Current rating of relay contacts is valad at voltage rating .

tim CET

"KDawg" wrote in message . cable.rogers.com...
Thanks for the info. I meant normally on as opposed to always on.
I have a 2 different relays in mind, both seem identical except 1 is .5 amp,
and the other is 20 amp.
What does the amp have to do with anything here ? Which one should I go with
?
THe ATX just needs a constant short between the green and black wire in
order to turn on and run. I don't think
either of these lines are used as major power supply lines. Just needs to be
connected thats all I know, thats what I want the relay to do, is keep the
connection, whenever the relay is getting power from another source
(96watt). As I have it now, I am using a paperclip to short the 2 wires, but
this requires me to use 2 switches to turn the system on, whereas I would
like to try accomplish this with 1 switch.

Also the 96 power supply is hooked up to a momentary push button to turn it
on. Once it is on, then I want the ATX power supply to kick in.

Regards,
KDawg
"default" wrote in message
...
On Thu, 21 Aug 2003 18:44:12 GMT, "KDawg"
wrote:

I want to run two computer power supplies, and have 1 turn on by a relay
when the first one is turned on.
The power supplies are 96 W and 250 W. I understand that a 12V DC always
on
relay is what I need, but I am not sure what amps it needs to be rated
at.

By always on you mean a duty cycle of 100%? (that would be correct)

The way it will work is this. I have a 96 Watt power supply that is
turned
on, and I want it to trigger an ATX 250 W power supply to come on as
well.
The relay will be powered by the 96 watt power supply, and the switch in
the
relay will connect the green and black wires of the ATX power supply so
it
will be on. If anyone has any information on what I should be looking
for, I
would appreciate it.

Regards,
KDawg

Your choices are to power the relay from a 12 volt voltage source in
the 96 watt supply, to keep the voltage of the relay low and make it
safer, or just run a 120 volt relay from the same switch that powers
the 96 watt supply (in which case why not just plug both supplies into
the same power strip, and leave the black and green wires connected at
all times?) Wouldn't work if the black and green is the reset line on
the ATX . . .

If you intend to sense the current through the 96 watt supply and turn
on the 250 every time the current exceeds a certain threshold - that
can be done but takes more explanation.

Your relay contacts need to be heavy enough to switch whatever current
the green and black wires of the ATX supply carry. I don't know that.
I assume they would be a logic level, in which case the current is
minuscule and the relay would need to be no more than a small reed
relay.

The relay you need is one that has a coil voltage for how you plan to
power it . . . . AC mains 120/240 VAC or a 12 DC or 5 DC volt source
from the 96W supply. (relay coils need to be AC types for AC
operation and DC for DC)

You need a "normally open" set of contacts on the relay. The contacts
stay open as long as the relay is de energized.

Never heard the term "always on" with respect to relays but it seems
to imply normally closed contacts - which isn't what you want. (the
ATX would come on when the 96W went off) Many relays have a contact
that can be wired either normally open or normally closed (single pole
double throw)


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