Topic: Electronics

Practical tips on electronic circuits, Raspberry Pi and Arduino

AlphaClock – old meets new

AlphaClock is the sort form of “alphanumeric clock” as the displays used can also show text.

A while ago I started to deal with the topic “micro controllers”. The first trials were with an Arduino micro which I also used to test old LED displays like the HDSP-2116 or DL-2416.

One advantage of the Arduino Micro ist that it can be plugged in directly to a breadboard and has a micro USB connector for data transfer and power supply. However from LCD2USB I also know the ATmega in a DIP package. For normal operation with external clock this controller only needs a crystal and two capacitors.

My idea was to combine an ATmega328P with two DL-2416 from 1987 and a DS3231 realtime clock module. The whole thing was also a project to learn to know the development environment as Visual Studio Code and PlatformIO as well as the way how the microcontroller works in terms of interrupt control and PWM.

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Hakko FX-888D

In August 2021 I bought a Hakko FX-888D soldering station. Hakko has been active in this area for decades and the products are considered to be of high quality and durable. The operation takes getting used to, but the set temperature is reached very quickly after switching on and also kept well under load.

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Shift registers

If you work with microcontrollers like the ATmega328 (Arduino Uno) or ESP8266 (Wemos D1 mini) and want to control many lines at the same time, it can become a problem that there are not enough outputs are available.

One solution are shift registers. More about this in my article about the 74HC595.

My little “electronics lab”

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.

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HDSP-211x for Raspberry Pi

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.

Revision 2

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.

Controlling a HDSP-2112

“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 :-).

HDSP-2112, test with Raspberry Pi

More about this along with a thorough documentation on the project page.