We already soldered one SMD kit, which allows you to practice the difficult task of soldering surface mount components. Now we try another kit with a bit more difficult components: two QFP44 ICs are in the kit as well as the usual array of resistors, capacitors, diodes and transistors. I will show you some techniques and tools for this job and hopefully we get better at soldering SMD stuff!
The 74 series of ICs is one of the longest running IC series. They encompass all basic logic functions and more. It is (almost) possible to build basically any digital circuit from chips of this series, without needing to use a micro controller. However it quickly becomes expensive as the transistor density of those chips is not very high. But they are a great way to learn about transistor-transistor-logic, or TTL. Today we’ll build the „TTL Graveyard Clock“, named as such because it… looks a bit like a graveyard, and this is also where 74 series chips go to die…? Kidding aside, this clock is an impressive design by Sergey Kiselev and a great way to learn soldering as well as to learn how 74 series ICs work. Plus in the end you get a fully functioning 24 hour clock with seconds!