CPU Display

I always wanted a display indicating the CPU speed of my processor. In practice it is quite difficult to do, so I made this (fake) CPU speed display like in the time of the old 486 PC's...

It's simply a couple of 7-segment displays and a bunch of resistors and jumpers to configure the displayed value.

It can be used with common anode (CA) or common cathode (CC) displays. (just inverse the applied voltage for CC, and diode D1 of course...)

With the given value of the resistors (150 Ohms) you can use red, green, yellow or orange displays (for red displays the segment current is about 15mA).

The schematic		The PCB layout
Download Schematic in Circuitmaker2000 format		Download PCB layout in Circad'98 format

The finished project

In action...

Mounted in a 5.25" bezel of my PC-70

My dream is to obtain some BLUE 14mm (0.56") displays as manufactured by Agilent (ex. HP) and Liteon...

Schematic for blue displays		PCB layout for blue displays
Download Schematic in Circuitmaker2000 format		Download PCB layout in Circad'98 format

Because of the higher forward voltage of blue LEDs (about 3.8V) I choosed to use the +12V rail instead of +5V.

With 750 Ohms resistors we obtain a segment current of about 10mA (as indicated by the manufacturer).

Note that blue displays are quite expensive (available for about €5.00/piece at Digikey (about 5US$)...without shipping costs)

Update: I ordered and received seven blue 0.56" Liteon LTS-5501 common cathode and seven blue 0.56" Liteon LTS-5503 common anode displays from Digikey...