Wednesday, October 26, 2005

Add Another Display to your Computer

Want a way to show a little more information on your computer without taking up any of that precious screen real estate and without shelling out the big bucks for another video card and monitor? A simple (and cheap!) HD44780-based (or compatible) character display can provide all this with a little money and a little effort. Connections are fairly simple - there are eight data inputs to the chips which connect to the eight output lines of (you guessed it...) the PC parallel port. The next bit is a little tricky, depending on your display. Some displays run off of +5 volts which is quite easy to get - it is quite common on computers and is also easy to generate using an LM7805 voltage regulator. Others, like the one that I used, require -5v to run which isn't quite so easy to find or make. I found a handy little circuit that uses the very common and quite useful 555 timer to convert an input between +6v and +35v to -5v.

There is a lot of software out there for sending text to the display - from a Linux kernel driver to a WinAmp plugin to all sorts of programs for displaying system information.

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