Diy power supply from an old computer psu

Theory

12 V and 5 V.

Wire Coloring

• Black: Ground (0V)
• Orange: +3.3V
• White: -5V (on older ATX power supplies)
• Red: + 5V
• Purple: +5V standby
• Blue: -12V
• Yellow: +12V
• Grey: power is on indicator
• Green: ON/OFF switch; turn DC on by shorting to ground.

Power Switch

This system need to reverse the GND and 12V line.

• Yellow cable (12V) on the colored terminal,
• a black wire (GND) to the pin opposite,
• the green cable (ON/OFF) to the centre pin.

Some power supplies need the grey and green to be connected together in order to run.

If there is the rear switch in the PSU, connect the green and black wires together.

In normal operation illuminated SPST switches have 3 terminals

• the centre pin: green Power ON/OFF
• one is indicated either by a different colour or labelled GND.
• The terminal opposite would normally be wired with 12V,

Power-on LED

• The grey (Power On) wire to the anode (long end) to the red LED.
• 330Ω resistor to the cathode.
• The black wire (GND) to the resistor.

Standby LED

• The purple (Standby) wire to the anode (long end) to the green LED.
• 330Ω resistor to the cathode.
• The black wire (GND) to the resistor.

The Fake Load

10W 10Ω resistor between 5V (red) and GND lines. The power resistor will give off a lot of heat and should be mounted on the metal wall for proper cooling (or a heat sink mount).

Consider using a lighted 12V switch, which will act as the load necessary to turn on the power supply, or replace the 10W power resistor with the cooling fan that was originally inside the PSU, be careful with the polarity though - match the red and black wires to each other.