LCD displays easy to use and easy to build

Posted on Feb 5, 2014

Here is an example which implements a clock in just 36 lines of perl code. It displays time and date and the upper right corner shows a little icon called `heartbeat`. The `heartbeat` is added by the LCDd server. This `heartbeat` icon blinks once in a while to indicate that the display is still alive. In lcdproc you can have more than just strings.

LCD displays easy to use and easy to build
Click here to download the full size of the above Circuit.

You get bar-graphs, scrollers, title bars. and text strings. At the beginning of the program you define those objects (they are called widgets) and then you fill them with data. It`s explained in the LCDproc Developer`s Guide from page 7 and on wards. #!/usr/bin/perl -w. # initiate the communication: print $remote "hello ";. # set our name and define a text string widget print $remote "client_set name lcdtime "; print $remote "screen_add scr1 "; print $remote "widget_add scr1 str1 string ";. while(1) {. $date = scalar localtime; # now write to the LCD: print $remote "widget_set scr1 str1 1 1 "$date" "; sleep 10; } The parallel port of a PC works according to specifications with 5V. If you now take a look at the datasheet of a modern LCD display (e. g from tuxgraphics: ) you will notice that even though the displays are big they need extremely little power. Only 2 mA ! With so little current it must be possible to power the display directly from the parallel port. The advantage is then that you do not need any extra power connector. It is just one LCD display with one connector to the parallel port. Very convenient. It is possible with a parallel port that really provides 5V. The problem is that there are some which do not follow the specifications. So how do you know if your parallel port is good enough for "self powered" solution Here is a little test: Now connect a 33K resistor to the parallel port between pin 1 and pin...

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