Charlieplexing Nixie Drivers

Nixies are great. Delightfully simple in their principle of operation and absolutely unmistakable in their aura. The hard-to-imitate aesthetics do come at a cost: they are a bit inconvenient to drive from modern electronics.

Many tried-and-proven nixie driver circuits can be found online. Using the classic 74141. With individual high-voltage transistors and shift registers. Or multiplexing the nixies to save on driver electronics? Multiplexing of nixies is a controversial topic: while the benefits are clear, many argue that nixies wear out faster due to the high current peaks when multiplexed.

This post isn’t about nixie multiplexing, though.

Lithium Battery Protection for Small Projects

Lithium cells haven’t become the predominant power source for mobile electronics without reason. Circuits for their—very necessary—protection are naturally plentiful as well.

One particular weak point of many protection schemes, however, is deep discharge protection. Common practice is to discharge LiPo/LiIon cells no further than 3 V to not risk permanent damage. Yet, most protection ICs cut off only at 2.5 V, and you thus have to rely on additional battery voltage monitoring.

Es ist Mittwoch.

Sometimes blog posts just have to sit in the drafts for a while. This one had the opportunity to mature for about a year. The actual project lies back about two and half years by now. The pictures I have of it haven’t got any better in the meantime, so I might just as well hit ‘post’ on this split-flap calendar I built for a friend.

Most of the time, it doesn’t do much. Once a day, it advances by one flap and ⅐ of the time, it announces the day of the week, Wednesday.