Meanwhile the printed circuit boards arrived which I have ordered from Aisler based on my first draft. The quality is fine. There where only production-related burrs that I could easily sand off.
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.
After my first experiment to control a single LED matrix display I extended this to two displays – and generally even more are possible:
More about this, see the project page.
“I’ve created fire!”
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.
I already experimented with this in 2013, however I stopped working on that and did not have a working setup ever.
This time I was more persistent – and it worked :-).
More about this along with a thorough documentation on the project page.
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.
Update May 2021
Finally I managed to control this thing properly :-). Also see my latest post about this.