You’ll find LCDs, or liquid crystal displays, in a huge variety of appliances, consumer electronics
and so on. Usually driven by a microcontroller, they’ve become very popular over
recent years for information transfer and instructions and (usually!) make
complicated equipment easier to operate.
But how do you get the message you want onto the LCD screen?
It’s not difficult, as this simple project shows.
The circuit (Fig.1) is quite straightforward. In fact, most of
the "work" is undertaken by the large integrated circuit hidden under the black
blob on the rear of the LCD module PC board.
All we have to do is provide that module with the appropriate
ASCII codes and these come from your computer’s LPT1, or parallel, port.
The project could have been as simple as that but we’ve gone
one step further and added a temperature control chip, the DS1620, which we can
use to make a simple but effective thermostat/thermometer in conjunction with
the LCD module. The remainder of the circuitry is mainly power supply – and even
that is very simple.