On an old fashioned bench a signal generator was once an indispensable instrument, but has now largely been supplanted by the more versatile function generator. Sometimes there’s a less demanding need for a clock signal though, and one way that might be served comes from [Rupin Chheda]’s square wave generator. It’s a small PCB designed to sit at the end of a breadboard and provide handy access to a range of clocks.
On the board is a crystal oscillator running at the usual digital clock frequency of 32.768 kHz, and a CMOS divider chain. This provides frequencies from 2048 Hz down to 0.5 Hz for good measure. It’s a simple but oh-so-useful board, and we can imagine more than a few of you finding space for it on your own benches.
This project is part of our awesome 2025 One Hertz Challenge, celebrating all the things which strut their stuff once a second. It’s by no means the first to feature a 32.768 kHz divider chain, and if you have a similar project there’s still time to enter.
Where all the 555s at?
The great octaves of 1Hz, very harmonious. It would be weird to have a famous math constants variation, 1hz, e hz, pi hz
It could be shifted into the acoustic range humans can hear by using 1, e, and pi kHz. Otherwise, we’re just shaking the room and hearing harmonics and other things going non-linear.
This looks like it would be a very handy budget test tool for a lot of devices.
They skipped 16 but put in 0.5?!? I’m curious to know why.
It’s the CD4060 chip itself that skips that output. I found this in a search of several datasheets. One one of them mentioned this:
“Missing CD4060 Outputs: Q0, Q1, Q2, Q10
You might notice that the CD4060 does not include outputs Q0, Q1, Q2, or Q10. While there’s no official reason provided for this omission, one possible explanation is that the CD4060 was designed as an upgraded version of the CD4040. To accommodate the oscillator and additional features within the same 16-pin design, some outputs may have been excluded.”
Good call. I looked at the data sheet for the CD4060 and saw skipped outputs, but they were not obviously in the right spot to skip 16 Hz. Then I looked up the schematic on the linked project and saw that the last two divide-by-2 operations are implemented with a CD4013. That shifts the skipped output up to 16 Hz.
The OnSemi data sheet has a nice side-by-side of the CD4040 and CD4060 block diagrams. There it becomes obvious that some outputs had to be skipped in order to free up pins for the oscillator.
I need to build a power amplifier to complement this project. The idea is to build a mechanical wave generator for a physics course using the simplest and cheapest electronics possible. Are there any projects available?