A Beautiful, Microcontroller-Free Digital Clock
Microcontrollers, and microcontroller development boards like Arduino in particular, have become so affordable and easy to use that it is now uncommon for us to see projects that don’t utilize them.
When you can get a development board for $3 that is packed full of features and hardware, there is very little practical reason not to use it. But sometimes you want to do things the hard way, if for no other reason than to gain a better understanding of electronics fundamentals. That’s the idea behind Harry Axten’s beautiful CMOS Clock, which doesn’t contain a single microcontroller chip.
Many of our older readers will probably shrug at that, because digital clocks have been made without microcontrollers since their very inception.
But you only need to take a look at the CMOS Clock to see why that’s no longer practical. You can purchase a tiny microcontroller that contains all of the hardware necessary to drive a digital clock, and it’ll be smaller than the digital readout itself.
That’s hardly the point here, though. Axten recently became interested in clock projects, and wanted to learn the basics by using simple logic chips instead of a microcontroller. It’s just a bonus that the CMOS Clock happens to look fantastic.
This clock is built in a way that used to be very common, with a standard 32.768kHz watch crystal. To bring that down to 1Hz that is much easier to work with, Axten used a 4060 counter and a 4013 flip-flop.
That means that every tick equals one second. It’s currently powered by an AC transformer, but doesn’t use that to keep time. The seconds are then counted by 4029 counters, which reset when they reach 60 (for seconds and minutes) or 24 (for the hours). The 4029 counters output a 4-bit BCD (Binary-Coded Decimal) value, which drives the 7-segment display decoder through a 4511 BCD.
All of those components are soldered onto a pair of custom PCBs, and those are mounted within a nice, minimalist glass dome with a wood base. If you’re curious about what you can build without using a microcontroller, this CMOS Clock is a great example.