The most important part of a computer architecture is a clock circuit. The circuit described here has the option to run freely in a-stable mode and also operate in single step debugging mode. In this post I will describe how to implement this design in KiCad and manufacture a double sided printed circuit board.
There is something about blinking leds. Numerous projects are created with the 555 timer chip. To continue the tradition I will describe in detail the creation of a 555 astable timer board that was designed in the previous blog post.
KiCad is a great schematic and PCB design tool. It is easy to learn and fun to use, above all it is free. In this blog post we are going to design a simple circuit based on the 555-timer chip in astable mode.
After the dry film is applied to the copper layer, it can be etched. There is an option to use ferric chloride (FeCl3), but it can not be reutilised and needs to be disposed. An alternative is to work with a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2), which can be regenerated with air and reused for the etching process.
If you can not afford a real NIXIE tube watch, there is an alternative. It is this 4-digit 7-segment LED watch kit. It costs less than 10 euros and you can find it on most Chnese resellers websites. It comes as a kit and you will need to do a bit of soldering and assembling.