PC Power Supplies

[redsierra]

Hi,
Can someone explain the difference and usefulness of -5 and +5 also -12 and +12volts in computer power supplies. What exactly is meant with minus or plus signs? Is there really a need for them to be inserted before the figure?

Thanks for your help, much appreciated.

 

[davenn]

Thats showing the voltage polarity relative to the 0V rail
so + or - 5V or 12V depending on the age of the PSU there may also be a 3.3V rail in there too.

cheers
Dave

 

[davelectronic]

The prefix just denotes that particular rail voltage, and the pin out for the ATX 20 / 24 pin molex connector for the supplys voltages for the mother board and other peripherals, the negative currents tend to be low in comparison with the + 3.3 + 5 and + 12 volt rails, there are other rails for other uses as well.

A picture diagram can be found on the web of all AT and ATX outputs.
Dave.

 

[Resqueline]

The power supply polarity is of vital importance to electronics, or else there be smoke. Compare it to the rotational direction of a lathe if you want.
The negative 5 & 12V supplies are very weak and are only remnants from a long past time when some obscure memory chips required dual power supply polarites.
Also the -12V is supposed to be used for the serial (RS-232) communication ports (no longer present in new computers).
The "distance" between +5V and -5V is 10V, and 24V between the +12V and the -12V.

 

[daddles]

Hi,
What exactly is meant with minus or plus signs? Is there really a need for them to be inserted before the figure?

The signs are very important; they tell you which way an electron will move in a wire subjected to that voltage. As mentioned, ignoring such vital information can result in smoke, damage, or an inoperable circuit.

 

[redsierra]

Re-pc power supplies

Thanks a lot for a quick response to my query regarding negative and positive voltages on psu. Your replies made it that much clear to a newbie. Tks once again