Convert ATX PS to Always ON

  • Thread starter Thread starter CharlesEF
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CharlesEF

Hi All,

I have an ATX case with a 500W power supply. I want to use this case
as a external SCSI drive case. The power supply has a On/Off switch
directly on it. So, my thinking is that I can hardwire (solder) the
green lead (Power On) to a black lead (Ground) and use the On/Off
switch to turn on/off the case when needed. Or, is the green and black
leads a momentary switch only? Should I connect it directly to the on
switch on the case?

Or, better yet, can I connect an AT style On/Off switch directly to the
On/Off switch on the power supply (thereby by passing/disconnecting the
On/Off switch on the power supply)?

Any and all help/ideas is greatly appreciated.


Thanks,

Charles
 
Hi All,

I have an ATX case with a 500W power supply. I want to
use this case
as a external SCSI drive case. The power supply has a
On/Off switch
directly on it. So, my thinking is that I can hardwire
(solder) the
green lead (Power On) to a black lead (Ground) and use the
On/Off
switch to turn on/off the case when needed. Or, is the
green and black
leads a momentary switch only? Should I connect it
directly to the on
switch on the case?

Or, better yet, can I connect an AT style On/Off switch
directly to the
On/Off switch on the power supply (thereby by
passing/disconnecting the
On/Off switch on the power supply)?

Any and all help/ideas is greatly appreciated.


Thanks,

Charles
Click to expand...

The "green/black" switch is active low and
normally held down by the mobo. You can use it
for an on/off switch.
 
Hi,

So, in other words I can connect an AT style switch directly to the
green/black leads and use it as the On/Off switch.

Do I understand correctly?


Thanks for your input,

Charles
 
Hi,

So, in other words I can connect an AT style switch
directly to the
green/black leads and use it as the On/Off switch.

Do I understand correctly?


Thanks for your input,

Charles
Click to expand...
You can connect a spst switch to pins 14 and 15
to enable and disable the supply.
 
Hi,

Thanks for your help with this. Since the AT switch is dpst I can use
1 side of the switch and tie it to pins 14 and 15. Also, the AT switch
will fit in place of the momentary switch that the case currently uses,
so I can use the case switch for on/off.

One more thing I just thought of. Should I apply a load to the un-used
power voltages? I understand a switching power supply needs a load to
function properly. Since hard drives only use +5 and +12 volts should
I apply a load to the other voltages? Or, will using only the 2
voltages be enough to make the power supply happy?

Merry Christmas / Happy Holidays, whatever the case may be.


Thank you very much for the help,

Charles
 
One more thing I just thought of. Should I apply a load to the un-used
power voltages?
Click to expand...

No, presuming these are normal drives, they'll already be
loading the 5V and 12V rails, which is what is necessary.
Ordinarily a PSU will only require 5V, or 5V and 12V, loads
and if the others float into off-spec values it is of no
consequence because the PSU is engineered to accomodate the
voltage range and the actual voltage level of unused
(unloaded) rails is just that- unused and effects no
equipment.
I understand a switching power supply needs a load to
function properly. Since hard drives only use +5 and +12 volts should
I apply a load to the other voltages? Or, will using only the 2
voltages be enough to make the power supply happy?
Click to expand...

Rarely one might come across PSU that monitor 3.3V rail,
even rarer the others. It's not common enough that one
needs to plan for it, rather checking afterwards if the
expected operation is not achieved with only 5V and 12V
loads. One possible indicator of such an alternate-rail
sensing is that on the other leads (besides 5V or 12V),
there are two wires going to the same ATX connector pin
position, one lower gauge (like 18-20) for delivering power
and one thinner feedback wire for sensing. Again, this is
not usually necessary to consider, only check if it doesn't
work as expected.
 
Hi,

Thanks for the information. I just wanted to ask someone who knows
more than me about these things.


Thanks for the help,

Charles
 
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