Some time ago I rediscovered my interest in electronics and recently done my first project. This project was created at the table where my PC is. However, this is not an ideal place to solder circuit boards or create designs with breadboards – I have to take the necessary parts and tools such as soldering iron, multimeter, etc. out of the drawer and then tidy up again afterwards.
On the project page about using LED matrix displays of the type HDSP-212x, I also showed an example setup with a Raspberry Pi. Now that I still have some of these displays, I would like to use them to build a real device in its own case.
Soldering the whole thing by hand on a perfboard would theoretically be possible, but is prone to errors and in the end you have only one copy. Nowadays there is a better solution for this: you design a circuit board with a program like KiCad and have it produced as a small series for comparatively little money.
My first draft for a board on which you can put four HDSP-211x next to each other already looks quite promising:
At AISLER, the production of three copies would cost around EUR 25 and would be ready in about a week. But before I actually do this, I’ll have to check the circuit diagram again and check whether adjustments are required for the power supply, since four modules together can have a power consumption of more than 1.6 A.
After taking a closer look at KiCad, I created a revised revision 2 of the layout:
The total size of the board is a bit smaller.
The mounting holes are now inserted as footprints and without soldier mask.
The HDSP-2112 is a module with a LED matrix display which displays 8 characters with 5×7 LEDs each. Due to the high power requirement of more than 2 watts this display is not suitable for mobile devices. The operating voltage is 5 volts and it will be controlled using a 8 bit wide data bus and a 5 bit wide address bus.
The Raspberry Pi can just be used as a small computer – but the really interesting thing is the opportunity to do experiments with self built electronic circuits. For this a breadboard is quite helpful.
Recently I got a number of LED matrix displays (HDSP-2112, eight characters, 5×7 pixels each). Used but in blameless condition – I just couldn’t resist ;-). The picture above shows the first functional test of one display with the character “A” which I “programmed” using hanging connections.