Way back in the 80’s – 1986 to be precise since I dated one of the PCBs – I made a ‘Record Time’ clock and it has lived in my parents kitchen ever since. Amazingly it’s still working 34 years later.
Original clock
![](https://www.picprojects.org/wp-content/uploads/2019/05/book48micros.jpg)
It is based on an Intel 8748 microcontroller and looking back now was quite an achievement. I had no development tools for it, just a book, the ‘Osborne 4 & 8 Bit Microprocessor Handbook’ which had a chapter on the 8748 including electrical spec’s and detailed instruction set information. From the information in that book I built a hardware programmer, wrote a two-pass assembler in BASIC along with a rudimentary linker and tool to create an Intel HEX formatted output file. At the time I had never used an assembler and just wrote tools to solve problems. I didn’t even no what a linker was when I wrote it, it was only years later when I got to use real development tools that I found out it was a thing!
The PCBs were designed by hand on to drafting film at 1:1 scale. You could buy PCB transfers with DIP pads and other pad styles on them, the interconnecting lines I drew by hand using Rotring drawing pens of various widths. It was really tedious and took a lot of planning with tracing paper and pencil overlays. There was no rip-up and redraw the traces, or move an IC to make more room.
Clock from rear, mains transformer under control PCB Initialled and dated PCB Very dusty!
I had a lot of trouble finding decent bi-colour LEDs that were both bright enough and diffused. In the end I found CQX95 LEDs worked but the company that had them would only sell me 100 LEDs.
Redux
I’ve always wondered how long it will keep going – is the EPROM going to fade away one day? I’ve often thought about doing a modern version but could never get motivated to do it. With access to loads of documentation, good development tools, easy to obtain components, CAD and cheap PCB manufacturing – there was no excuse really. Anyway, having done the ‘Tacho Clock’ over the last few months that had some code I could reuse, I spent a Bank Holiday weekend messing about with some ideas for ‘Record Clock Redux‘.
![](https://www.picprojects.org/wp-content/uploads/TachoClockProjects/rc2-a.jpg)
As you can see above it’s still a work in progress, the code is pretty much done but I want to get a PCB designed and also sort out the construction of the clock.