power supply units

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power plugs and cables

Large, high-end severs come with thick, heavy power cables (starting at 15 gauge ). Heavy gauge power cords have significantly lower resistance and waste less power. But is the power savings significant?

IEC 60320 is a specification for non-locking (held in place by friction only) power connectors.

IEC C13 and C14
this is the most familiar plug (C13) and socket (C14) used by desktop and server power supplies since the dawn of time. The C13 plug carrying AC power is female. The inlet socket to the power supply is male.
IEC C5 and C6
a cloverleaf pattern. Sometimes called Mickey Mouse plugs. These are often found on laptop power supplies and smaller peripherals.

convert ATX PSU to a general purpose power supply

Obtain an ATX PSU.


     BLACK: GND ground

     GREEN: Power on. Ground this line to turn ON.

     YELLOW: +12V. On newer power supplies you may need to attach a 22Ω 10 Watt resistor to GND as a dummy load. Switching power supplies usually need at least some load to operate properly.

     RED: +5V. On older power supplies you may need to attach a 5Ω (or 4.7Ω, 4R7) 10 Watt resistor to GND as a dummy load. Switching power supplies usually need at least some load to operate properly.

     ORANGE: +3.3V

     BLUE: -12V

     PURPLE: +5VSB (standby). This provides low power 5V even when "off".

     WHITE: -5V (rare)

     GRAY: Power OK signal line. Attach an LED in series with 330Ω resistor for a power ready light.

     BROWN: +3.3V remote sense. This may not be necessary for all applications. You should attach this to the +3.3V

     ORANGE line. The attachment point should be near the load, not just inside the PSU. This allows the PSU to measure the resistance of the power lines leading to the load and fine tune the voltage level. For long power lines the voltage drop can be significant.