Do you think that the printer is displaying messages, when it is connecting with computer? Well, how about you break the rules and create a standalone LaserJet printer that can display custom messages without a computer?
It might sound a little bit nonsense, but you can really make it here! In this case, you’re going to use the HP LaserJet printer, where it has a little display and you can use PJL (Controlling language) to change everything that being displayed on it!
First of all, you need to use the Centronics parallel port, as it’s easier to be implemented than others. For the microcontroller, an ATTiny2313 will be the best part to send signals through a parallel port.
You can connect the AVR directly to a Centronics-connector, where it can be mated with the socket on the LaserJet. By the way, a capacitor is needed in this project to filter the power supply.
You just soldered all the Centronics-connector, an AVR, a 20-pin IC socket and a capacitor together to a nice and compact unit. After it, you’re done and can start testing out the result…
Note: This project is very cheap and easy to install, and it can be disposable as well!