Parallel port switching device for pp_powerSwitch

Schematics

Components

Basics

• 8x NPN Transistor: BC547A or 2N2222A
• 8x Diode 1N4002 (to protect the relay)
• 8 resistors 4700 Ohm
• 8 Relays (I use relays which can handle up to 7 A)
• 3-way switch (1: computer controlled; 2: ON; 3: OFF)

Additional

• Parallel port connector
• a nice case
• connectors
• a transformer (for your 12V relay)

Pictures

• Inside
• Front
• Back

At last

Most information on this page is based on the COFFEE-HOWTO. I recommend reading this first, before building anything.