An LED Clock Without a Micro-controller

As it seems, I like to make different clocks. I have built and designed numerous electronic and mechanical clocks and this one is another one. My first electronics clock required several iterations and I learned a lot.

The presented design is improvement of the older design – it is smaller and cheaper to build than the previous versions. Additionally, I have documented the process much better this time.

The clock is electronic, without any microcontroller. The time is generated from a 32.768 kHz crystal and by counting the crystal oscillations the time could be shown. The numbers are constructed with LEDs in a seven-segment display formation.

In the following the BOM is introduced, thereafter the design is introduced and eventually the assembly process is shown.

Step 1: BOM

Everything through hole components (I got everything from Aliexpress)

• 74HC393N - 8 pcs
• 74HC32N - 3 pcs
• 74HC08N - 3 pcs
• 74LS47N - 6 pcs
• NE555N - 1 pcs
• 8-bit switch - 3 pcs
• 6mm button - 2 pcs
• Resistor 10k - 9 pcs
• Resistor 1M - 5 pcs
• Resistor 1k - 1 pcs
• Resistor 560Ω - 52 pcs (follow the comments in the end, I used 560Ω)
• Capacitor 100n - 15 pcs
• Capacitor 16p - 1 pcs
• Capacitor 8p - 1 pcs
• 32.768kHz crystal - 1 pcs
• Led - 128 pcs (you can use any color you like, 3 or 5mm LEDs, I used 5mm)
• M3 screws (>5mm) and nuts - 4 pcs
• 3 PCBs

I would strongly recommend using IC sockets instead of directly soldering the components

Step 2: Design Explanation General

Step 3: Design Explanation - 32.768Hz Signal

Step 4: Design Explanation - 1 Hz Signal

Step 5: Design Explanation - Clock Logic

Step 6: Design Explanation - Logic Schema

Step 7: Design Explanation - 7 Segment

Step 8: Design Explanation - Voltage and Power

Step 9: Design Explanation - PCB

Step 10: How to Solder

Step 11: Ready Clock

Step 12: Conclusion

I hope this instructable was helpful and interesting to read.

Maybe it can inspire other people to use counters or build their own clock.

If you would like to purchase the PCB gerber files then follow this link to my etsy shop:

https://www.etsy.com/shop/DrTonis?ref=seller-platf...

Comments

[kcraske]

As I like clocks I read anything to do with them intently, looking to understand how they work etc. Unfortunately with this article, as the explanations are actually images, the links to further reading do not work. Any chance of an update.
Still want to build this.

[drtonis]

There is a PDF file at the beginning.

[kcraske]

Brilliant. Thanks. 1 step closer to an order from AliExpress and JLCPCB. Such a pity local suppliers are so expensive.

[kcraske]

Fantastic. It's so good to see a clock without the microprocessor.
Way back when I was at my last year at school when I was 18 I built a 4 digit clock using the new thing in electronics, TTL logic. The time base was the mains frequency and the display, Nixie tubes. However, is this design still a digital clock as the display is not analogue?
Really like your clock and might give it a go and I see you make it easy by making the Gerber files available. Great.

[MikB]

I agree, not only is the display (literally) digital, but the clock is almost entirely digital logic.

From the title, I was hoping for something involving actual analogue electronics (op-amps, R-C circuits, etc. maybe even moving-coil meters for the readouts) -- so I think the only way to make it right is to set that as a challenge for your next one ;)

[drtonis]

I see the point you are making. For me digital means more with a display, but technically you are right.

[MikB]

Absolutely. There are two contexts of digital/analogue here.

Digital does mean "with a display". Of digits. This is a digital clock by that definition. Same would apply to nixie tubes, LED bargraphs, coloured marbles etc. An analogue clock would have sweeping/micro-stepping hands (or faux-display of these, in some way).

Digital also applies to the electronics used. It is a digital clock by that definition too. 74 digital logic! No part of this is an analogue clock (apart from the 555 chip!)

It is still a cool clock, but I must demand a refund, as "significantly not as described" :)

[kcraske]

Actually MikeB, I would not allow micro-stepping hands as being analogue. Sweeping hands are needed. I might allow a bit of poetic licence on that one. Time is actually analogue, digital clocks are counters that cannot count. 55,56,57,58,59,100,101,102. And insert a decimal point to suit.

[kcraske]

The display is digital in this clock. Analogue means continuously variable. The display in this clock is not continuously variable but changes in increments, in this case every second. A 'true' analogue clock has a display which continuously changes such as a motor driven (not stepper motor) clock.
Would not a better title be 'Digital clock, no microcontroller'.
In any case, I might still build it to add to my collection of various electronic clocks I have built.