The Depeche Mode ‘Singles’ Clock Challenge

While repairing an office treadmill, Andreas, a friend who also volunteers in our non-profit repair shop, was fascinated by its large seven-segment LED displays. He remembered the covers of Depeche Mode’s ‘Singles 81>85’ and ‘Singles 86>98’ compilation albums. As you can see from the picture above, the album covers feature giant, red, 7-segment displays mounted on PA speaker tripods (courtesy of Photoshop, I assume). I admit that I am not too much into Depeche Mode; Andreas, on the other hand, is a fan with capital F, A, and N. He challenged me whether it might be possible to build a digital clock having a similar look, just smaller. Since he had already helped me with several of my own projects – and I liked his idea’s fun factor – I accepted the challenge. It became a rather time consuming project that resulted in my prototype shown in the picture above.

As can be seen from the picture above and the video clip in step 6, my camera cannot capture the red display colour, and it comes out rather yellowish. But in reality it is a beautiful, pure red.

You might have read in some of my earlier ‘bles that I try to do the things as cost-efficient as possible (which should, in fact, be a part of every engineer’s job description). I soon had the idea to (ab-)use a cheap, China-made, 24-hours, 6-digit quartz clock kit. I even had one of these in my junk box already; it is a very simple, no-frills, no-comfort design using several digital CMOS chips. It works nicely, if not overly accurate.

About half a century ago, when 7-segment LED displays were new, they were small, dim, rather expensive, and required a current of at least 20 mA per segment. These days you can fortunately find much larger, much brighter, and much cheaper displays that require much less current. The ones I selected (see ‘Supplies’ section) feature 30 mm high, bright, red digits, and when combining them with 6 mm dia. aluminium or steel tubes (and quite a bit of other ideas and hardware), the proportions can be made to rather nicely match the Depeche Mode cover artwork.

So, the electrical/electronical part of this clock is easy-peasy, even if there are some stumbling blocks.

A first test of the assembled clock – with one of the small digits replaced by one of the new, larger ones – was successful (see the video clip below). The mechanical part became, for me at least, rather more difficult. More about that later.

As in most of my instructables, the steps below only are descriptions of how I solved particular problems. There will for sure be different – and perhaps better – solutions that can be thought of. But I have to make do with the ideas I have. If a better one pops up, I will post an update report later :-) And if you yourself should know of a better solution, please let me know about it in the comments section.

Materials

Please note: The links given below are valid at the time of writing; no guarantee that they will still be valid tomorrow or the day after... but Google is your friend.

The AliExpress product descriptions are heavy with unintended humour, regardless whether in English or in German – they say, for instance, ‘bit’ instead of ‘digit’, and ‘welding’ (Schweissen) instead of ‘soldering’ :-)

1. 6-digit digital clock kit with 7-segment LED displays (common-cathode, in our case), such as

https://de.aliexpress.com/item/1005006319997582.html?pdp_ext_f=%7B%22sku_id%22%3A%2212000036749169467%22%7D&sourceType=1&spm=a2g0o.wish-manage-home.0.0&gatewayAdapt=glo2deu

1. 6 cheap, red 7-segment LED displays, 30 mm digit size. Make sure that they are of the same type (common-cathode or common-anode) as the small ones contained in the kit, such as

https://de.aliexpress.com/item/32726158283.html?pdp_ext_f=%7B%22sku_id%22%3A%2212000028731076206%22%7D&sourceType=1&spm=a2g0o.wish-manage-home.0.0&gatewayAdapt=glo2deu

1. 5 VDC wall wart, e.g. a retired USB smart phone charger; alternatively, perhaps a wall wart with adjustable output voltage, approx. 3 to max. 15 VDC (junk box)

The current-limiting resistors for the display segments on the clock PCB are designed for a 5 VCD supply, their current value is 470 Ω. They limit the segment current to about 6...7 mA for single-LED segments (as in the small, original displays contained in the kit) or about 2.5 mA for dual-LED segments (that is sufficient for the larger displays suggested here). If you use a higher supply voltage, they have to be adapted accordingly. To reduce the brightness, the voltage may be somewhat reduced.

1. 12 x 5-pin female pin headers (you cut them away from the 40-pin sticks), and
2. 12 x 5-pin male pin headers (you cut them away from the 40-pin sticks), such as

https://de.aliexpress.com/item/4001122376295.html?spm=a2g0o.order_list.order_list_main.118.33ae5c5fNCNs2R&gatewayAdapt=glo2deu

1. Some matrix board leftovers, cut to size (dimensions see later), such as

https://de.aliexpress.com/item/1005009057589345.html?spm=a2g0o.productlist.main.44.4cd44a78sht5Aa&aem_p4p_detail=2025081516011011625731869437720002312030&algo_pvid=fd32b609-fe32-4e79-addd-ffae44339824&pdp_ext_f=%7B%22order%22%3A%223%22%2C%22eval%22%3A%221%22%7D&utparam-url=scene%3Asearch%7Cquery_from%3A%7Cx_object_id%3A1005009057589345%7C_p_origin_prod%3A&search_p4p_id=2025081516011011625731869437720002312030_11

1. 6 circular 8-pin ‘aviation grade’ plugs and sockets, such as

https://www.amazon.de/dp/B07NYYKQVZ

1. 6 wooden dowels 10 mm dia., cut to length (18 mm) (I tried it with some round-head screws and recessed nuts; it works, but if you have some wooden dowels available this is much easier)
2. Some 6 mm dia. anodised aluminium (or stainless steel) tube, wall thickness 1 mm (hardware/DIY store). The aluminium tube is much easier to be worked, a steel tube is sturdier.

I purchased some tubes from Amazon, but they are not anodised and therefor very sensitive to scratches. Apart from that, they are slightly bigger than 6 mm.

1. Some 8 mm dia. aluminium (or stainless steel) tube, wall thickness 1 mm (hardware/DIY store) (optional)
2. Some (12) M6 rivet nuts (optional)
3. A piece of 20x20 mm ‘Fullerkreg’ aluminium profile, such as

https://www.amazon.de/dp/B08JL8HLXT

1. 18 M4 slot nuts (sliding nuts) matching the profile above

https://www.amazon.de/dp/B09XK67ZKC

1. Thin insulated, stranded wire (black, brown, red, orange, yellow, green, blue, violet), max. dia. 1.1 mm, each min. 3 m long.

The following link is valid for the black wire; the other colours can be found there easily:

https://www.reichelt.com/ch/de/shop/produkt/kupferlitze_isoliert_10_m_1_x_0_14_mm_schwarz-10298?nbc=1

1. Mounting hardware (M4x6 screws, M4x6 set screws, M3x6 countersunk head screws, 3 mm countersunk head SPAX screws, M3 hex bolts, M3 nuts, M3 washers, M4 nylon washers); the respective amounts and exact dimensions depend on your individual mechanical solution (hardware/DIY store)
2. Aluminium sheet, 40x20 cm, 2 mm thick (Amazon or hardware/DIY store)
3. Wooden board (e.g. MDF or plywood), no less than 25 mm thick, 40x20 cm (hardware/DIY store)
4. Acrylic glass, approx. 19x39 cm, about 5 mm thick (junk box or hardware/DIY store) (optional)
5. Some scrap wood (e.g. MDF, plywood, or even acrylic glass, or some fat aluminium sheet), approx. 8-10 mm thick, about 6x12 cm (cut to size, dimension drawing see later) (junk box or DIY store)
6. Some florist’s wire, approx. 0.6 to 0.7 mm dia. (Florist’s or DIY store)
7. Fimo ‘soft 8020’ oven-bake modelling clay, black (Amazon or DIY store) (optional)
8. 2 momentary switches (one ‘make’ contact each; already contained in your clock kit. Don’t solder them to the PCB)
9. 1 slide or toggle switch (single-pole, single-throw, SPST – that is, one ‘make’ contact; the one contained in the clock kit may be a little bouncy, see following text. Don’t install it on the PCB)
10. Socket for the power supply barrel plug, matching the plug of your wall wart (I used a USB-C socket on a small break-out board, as it was easier to install in my design) (junk box)
11. Some aluminium bracket or some FR4 perf board/matrix board (mounting base for switches and power supply socket) (junk box), 25 x 25 x 100 mm (junk box)
12. Some bare, tinned copper wire, about 0.6 mm dia.
13. Some thin Teflon insulating tube (optional)
14. Silver (spray) paint (e.g. for automotive alloy wheels; I used Hammerite paint from my junk box that had to be applied with a brush – no spray can mess in my workshop:-))
15. Wood primer (optional, needn’t be in spray form, I prefer the one that can be applied with a small neoprene foam roller)
16. Black paint, or granite-look spray paint (optional) – or any other desired colour (I had some light grey paint available in my junk box that was applied with a small neoprene foam roller)
17. 4 auto-adhesive rubber feet
18. Glue stick for paper
19. UV-curing superglue, such as ‘UHU LED-Light Booster’

Tools

- For assembling the basic digital clock

1. Component bending gauge
2. Soldering frame
3. Small wire cutter
4. Soldering iron with a fine tip (I am using my faithful Weller Magnastat soldering station that has served me since more than fifty years – not exactly cheap but worth every penny); see here: https://www.instructables.com/Revival-and-Upgrade-of-a-Vintage-Weller-Soldering-/
5. Solder; easiest to solder with is the old-fashioned, but no more widely used, tin/lead alloy (63 % Sn, 37 % Pb) that unfortunately fell from grace due to its lead content; it still may be used for DIY and medical applications. Current lead-free solders are not that easily soldered; they require a higher soldering temperature and usually some more flux.

- For the display tripods

1. Metal hack saw (or circular metal saw)
2. Stationary belt sander
3. Peening tool
4. Table drill with machine vice (or power drill and vice)
5. 4 and 6 mm drill bits
6. Vice
7. Triangular scraper
8. Soldering iron
9. Screwdriver(s)

- For the mounting base

1. Peening tool
2. Table drill
3. 3 mm drill bit
4. Countersinking cutter
5. Step drill bit; largest step min. 16 mm dia.
6. Screwdriver(s)

I tried to design a digital clock that looks, if not exactly identical, then at least similar to the one depicted on the album covers. For such a not-too-simple design, a draft on paper (or in a vector graphics application) is mandatory, see the first picture above and the pdf file downloadable below. When printing this file on a DIN A3 sheet using ‘page scaling: none’ you can see the actual dimensions of the design. Andreas took my sketch and built a mock-up of one of the digits from cardboard and skewer sticks :-), see the second picture above.

While doing that, several questions popped up that needed answers before proceeding, resulting in a kind of a target specs list:

1. The display size should be in proportion with the diameter of the tripod tubes. A different design, btw, using displays with a numeral size of 45 mm was rejected, because the mounting base would have been 60 cm wide and 30 cm deep which was considered somewhat large. With the 30 mm high Displays the mounting base has a more moderate size of 40 x 20 cm.
2. Each LED display should be pluggable into its base – because nobody knows about the reliability of the cheap, China-made displays, and perhaps the clock needs to be disassembled during transport.
3. The LED display assemblies should be able to be disassembled so that any repair becoming necessary will not be too complicated or time-consuming.
4. The minimum possible inner diameter of the tubes used for the tripods is defined by the thickness of the eight insulated, stranded wires that need to be threaded through the tubes (one wire for each of the 7 segments, and one for the common cathode). The wire I recommend has a diameter of 1.1 mm, and in the tubes with an inner diameter of 4 mm it is a tight fit, as the 4th picture above illustrates.
5. The three legs of the tripod will be a kind of simple embellishment without any mechanical supporting function. They should be collapsible for easy transport.
6. The display-and-tube assembly must be pluggable into sockets on the mounting base for easy transport, and perhaps for repair in case of any accident.
7. The mounting base should be as compact as possible; the dimensions resulting from my sketch (see the first picture of step 3) are 40 x 20 cm. The thickness is no less than 25 mm so that the clock PCB has sufficient room.
8. The top cover of the mounting base must be thin enough so that the six male connectors (one per display tripod) can be attached to it. Aluminium sheet with a thickness of 2 mm was considered ok, it will be attached upon the base made from MDF. The mounting holes for the clock PCB will depend on the PCB of the clock kit actually used.
9. For the bottom cover I suggest a piece of transparent acrylic glass. I had a broken cover from a vintage vinyl turntable waiting in my junk box for future missions, and I cut it to the correct dimensions.
10. The wiring between the 8-pin sockets and the clock PCB, both installed in the mounting base, must be pluggable into the PCB.
11. The displays should be pluggable as well in a contraption providing mechanical and electrical support.

When starting such a project, some electronics tinkering experience is mandatory. Please don’t blame me if something goes wrong due to lack of experience! Fortunately, these kits are available at such a bargain price that rookies might consider purchasing two of them at the same time – which is to be recommended in some cases anyway, when there is a minimum order amount to ensure that shipping becomes free of charge.

On the other hand, this clock circuit is more or less foolproof – as long as you know your resistor colour code, and as long as you take care of correctly placing the polarized elements (ICs, diodes, electrolytic capacitors). Please don’t forget to observe the usual precautions for handling CMOS IC chips during assembly. And of course, remembering which end of the soldering iron gets hot helps a lot.

When buying in China, you will normally get neither circuit diagram nor component layout drawing nor assembly instructions in a western language. We don’t like that, but it can’t be helped. Fortunately I found a second manufacturer selling an identical circuit on a somewhat smaller, double-sided PCB who provided a nice circuit diagram in .jpg format (see above). Anyway, the component designators and values are silkscreen-printed on the PCB, so the kit is rather easy to assemble nevertheless, even without access to a BOM or a circuit diagram.

If no IC sockets are provided with your kit, I strongly recommend purchasing some and using them – troubleshooting a circuit is much easier when the ICs are not soldered-on but plugged into sockets.

In some kits, additional ‘colon’ LEDs are provided between the hours, minutes, and seconds sections. These are not used in our application, you can put them in your junk box for later projects.

Assembling always starts with the lowest-profile components – wire bridges (if required), diodes, and resistors. Using a solder frame is recommended; mine is old but still useful, since it is equipped with a cover that has a foam rubber layer that presses the components down after having inserted them, so that they won’t drop out when turning the PCB over. You should cut the excess wires before soldering them to the PCB. This is in fact standard practice because the wire ends will get an airtight cover when soldering, and no corrosion can creep in between wire and solder.

DO NOT solder the original, small 7-segment LED displays. Instead, use some 5-pole, female pin headers in their locations. They will be used later for connecting the wires going to the larger displays on their stands. Details about that will follow. These headers can, of course, also be used as sockets for plugging-in the small, original displays for a first test, after which the displays can be easily removed again. Instead you might use some wide 20-pin DIL sockets. They need to be cut in half when installing on a different clock kit PCB, as shown in the 4th picture above.

I don’t recommend to install the switches contained in the kit on the PCB but on a small, extra rear panel instead, as mentioned in the ‘Supplies’ section; you may connect them temporarily to their dedicated solder pads with some thin insulated wire for the first test. Be aware of the fact that the momentary switches also provide bridges for the circuit, required for correct function of the clock; these bridges must be added by using some extra pieces of wire (highlighted in red in the 5th picture). The slide switch contained in the kit for stopping/starting the clock is not beyond reproach, it has the tendency to 'bounce'. A bouncing switch produces an unpredictable series of short impulses, both when closing or opening its contact, which is not suffered gladly by some digital electronics. I replaced it by a push switch from my junk box that showed a better behaviour.

Once the PCB is populated, everything sits in its correct place, and is carefully soldered, it’s time for one (or even better, multiple) visual checks. Don’t forget to check for excess solder between the IC pins! Placing the PCB towards a light source and watching from the solder side can be very helpful when doing this check. And as soon as everything seems to be ok, connect your wall wart with the correct polarity (!) to the PCB, and then to a mains outlet. If you don’t get some (random) numbers on the display, switch off immediately and try to find the fault.

If everything is ok, you can set the correct time using the ‘start/stop’ slide (or push) switch and the ‘hours’ and ‘minutes’ momentary switches. You might even let the clock perform a kind of ‘burn-in’ test in this configuration, because it will take some time until the mechanical part is ready for installing the electronics.

This was, for me at least, the easy part. The design details of the mechanical part and the modifications required for matching the PCB to the new exterior design will be dealt with in the following steps.

The base is made from 25 mm MDF and a top cover made from 2 mm aluminium sheet. The cavity in the MDF board depends on the size of the clock PCB and the positions of the six 8-pin connectors. The MDF can be painted in your preferred colour, I selected a light grey, as shown in the last picture with a bottom view of the assembled base.

The top cover is drilled according to the sketch of the mounting plate (can be downloaded in PDF format below) and is attached with some countersunk SPAX screws to the MDF base. Please note that the mounting holes for the clock PCB and for mounting the top panel to the MDF base are not included in this sketch since they depend on your actual design and dimensions.

If desired, a piece of acrylic glass can be attached to the bottom, for protecting (and showing off) the innards. If attaching it with some screws it might be a good idea to use one nylon washer per screw as a spacer between acrylic and MDF, preventing the acrylic from sticking to the paint.

The clock PCB is attached upside down to the top cover (that is, in normal use it hangs downwards within the base), using four hexagonal spacers with M3 thread, about 10 mm long. When installing the clock PCB in such a way that its solder side faces towards the top cover and the component side faces downwards, the hrs-min-s sequence is maintained, and the wiring to the 8-pin connectors remains as short as possible.

I provided a small rear panel that is, in my case, made from matrix board and attached with four SPAX screws to the MDF base. It contains the three switches for setting the clock and a USB-C break-out board for connecting the power supply. This is in fact not recommended because it bends very easily; in a next iteration there will be a standard socket for a barrel plug. The picture above shows the earlier, black rear panel equipped with a barrel socket and toggle switches; these switches proved to produce switch bouncing that was not suffered gladly by the digital electronics. I used better switches then, but they had to be installed on a piece of matrix board.

You need to be careful when fixing this panel to the rear of the base since the MDF easily splits when inserting screws to its face; don’t forget to pre-drill guide holes.

The small, original LED displays will not be used. Instead, I provided custom-made adapter plugs made from small pieces of matrix board (some of them even recycled) and two 5-pin male pin headers in such a way that the plugs can be inserted in the display sockets. For dimensions see the 4th picture above.

Solder thin stranded wires to the 8-pin connectors that will be connected to the custom plugs later. I used wire colours adhering to the standard resistor colour code (with the exception of the black CC wire). The seven display segments have standard designators ‘A’ to ‘G’, and ‘DP’ for the decimal point, see the drawing and the wiring table above. Drop the six connectors into their holes in the top cover so that the wires face downwards and tighten their nuts. Before doing that I temporarily covered the scratch-sensitive upper face of the aluminium sheet with painter's tape in order to protect the surface from damage. Then connect the wires to the custom plugs that are already plugged-in in place of the small LED displays, again according to the wiring table above.

I doubt that the circular, 8-pin connectors are indeed approved by aircraft manufacturers, although their product description says ‘aviation grade’ :-) – but they are a bargain and more or less fit for our purpose. For our prototype, they are ok, but in series production, I might select a more sturdy solution, since unfortunately the mechanical fit is a bit wobbly even after tightening the coupling ring.

Guess what happened when I tested the finished base unit together with the first pluggable display unit. Right: There was absolutely nothing, not a single display segment was illuminated. Some diagnostics time later, the culprit was found. My wiring was almost ok, but I had missed the fact that the original, small displays have an internal connection between pins #3 and #8, i.e., they have two common-cathode pins. The clock PCB, however, only feeds supply voltage to pin #3. My black wire however went to pin #8 of the custom plug – which means that this supply voltage did not reach pin #8 of the circular 8-pin connector. The easiest remedy I could think of was connecting pins #3 and #8 on the clock PCB’s solder side, using some short, insulated wire - see the next-to-last picture above; after that, the display illuminated nicely.

The last picture is a bottom view of the completed and wired base.

For each display stand you need the circular connector, a 23 cm length of the 6 mm aluminium tube, a 20 mm piece of the ‘Fullerkreg’ aluminium profile, 3 sliding nuts, 2 M4x12 screws, 1 M4 set screw, the display adapter PCB with 2 x 5-pin female pin headers, and the display itself, of course. The wiring from the plug to the adapter PCB is done with insulated, stranded wire that has to be thin enough so that eight pieces of this wire fit into the 6 mm tube.

Cut six 20 mm long pieces from the Fullerkreg profile and smoothen the edges with a small file or a triangular scraper, as shown in the left piece of the first picture. Drill a 4 mm hole in one side. The longitudinal hole must be increased to a diameter of 6 mm, so that the tubes can be threaded through it. Please take care that the profile is tightly fixed in the machine vice when drilling in order to avoid bloodshed.

Prepare the display adapter. Drill two 4 mm holes into the piece of matrix board cut to size, and solder the female pin headers according to the drawing above. The Fullerkreg profile is attached to the matrix board using two M4 screws and two sliding nuts. The 4 mm hole in the profile must face away from the matrix board.

The tripod is decoration only and has no mechanical function. Per tripod you use 3 pieces of 6 mm aluminium tube (65 mm length) with a small hole next to one end, and a small sphere of black Fimo attached to the other end, the tripod adapter, and some florist’s wire. Further embellishments can be made from short pieces of 8 mm aluminium tube and/or some M8 rivet nuts that have their threaded hole increased to 6 mm. For drilling the rivet nuts, a machine vice with a jig made from a piece of scrap woods must be used, in order to clamp the nuts while drilling. Be careful to not touch the nuts right after drilling, they become quite hot due to the friction and the thermal insulation provided by the jig.

The tripod adapters are made from 8 mm thick MDF. Print the template (see PDF file below) on plain paper and attach it to the MDF using a glue stick. Once dried first drill the 6 mm holes, then cut the six pieces out using a (small) band saw, after which the paper templates can be peeled off. Make sure that the holes are large enough to nicely fit over the 6 mm tubes later. The lateral slots are sawed with the band saw as well, but due to the hexagonal shape a sawing jig is mandatory, as shown in the photographs. Once finished, paint them silver; I used some leftover silver Hammerite paint.

The three short aluminium tubes that are used as the tripod ‘legs’ receive a hole of about 1 to 1.5 mm diameter that allows to fix them to the tripod adapter later. Use a simple jig with a groove that helps keeping the tubes in place while drilling. The other end of the tubes get little spheres made from black Fimo modelling clay. The tubes with the black spheres attached are then baked according to the Fimo instructions. To hold them in place while baking, use a scrap piece of wood with sufficient holes to insert the tubes.

Attach the legs to the tripod adapter using a loop of florist’s wire. The wire is threaded through the holes in the tubes and the slot in the tripod adapter, and the legs are inserted into the adapter’s slots. The wire ends are simply twisted together, bent down and cut with a wire cutter.

Fixing the shells of the 8-pin female connectors to the long aluminium tubes is not exactly easy. First remove the black connector inserts by removing the tiny screw, and make sure not to lose these. The inserts can be pulled from the shells after rotating them a little bit.

Make a jig from a thick piece of scrap wood and drill holes in the correct places to hold the six tubes in a parallel position, vertical to the base. You can take the exact positions of the hole centres from the drawing for the base. Insert 18 mm-long, 10 mm dia., wooden dowels instead of the black plastic inserts. Then attach the shells to the male connectors already installed in the clock's mounting base and tighten their coupling rings. You can somewhat loosen the cable clamps at the end of the connector shells and insert the end of the tubes. Slide the jig over the six tubes, then tighten the cable clamps again. The tubes will not be fixed sufficiently with the clamp only, so I suggest using some additional glue to stabilize them. I used the UV-curing UHU superglue that is a little viscous and can fill gaps; make at least two rounds, shine on the glue with the UV light source and give it sufficient time to set.

Before purchasing wires I checked whether eight of them might be threaded together through the 4 mm bore of the aluminium tubes. I found some insulated wire with a diameter of 1.1 mm, and the easiest way to check this was by making a quick drawing, see the 1st picture above.

The wiring itself requires some patience. You need six times eight wires, that is, forty-eight in total, each of which having two ends, that is, ninety-six ends in total (in fact, it is the same number of wires and wire ends you already used for the connection between the clock PCB and the connectors in the base. These wires should be about 35 cm long. Strip and tin one end of each wire and solder them to the black contact pieces. In the picture above you can see the tiny pin numbers on the solder-lug end of the connector. The other end of the wires will be soldered later; use wire colours adhering to the standard resistor colour code (with the exception of the black CC wire). Refer to the wiring table above.

Inserting the wires into the small tubes is a bit tricky. It gets easier when the inside of the tube end is smoothed with a countersink or a triangular scraper. The wires need then to be exactly in parallel. If they are crossing or twisting, they cannot be pulled through the tube without being damaged. I made some templates to keep them in parallel while threading them (see PDF file below). Print the template on plain paper and glue them to a bit of not too heavy cardboard with a glue stick. I used a scrap cardboard piece from one of my favourite yoghurt containers :-) I had no colour printer available, so I coloured the templates the cheap way, using felt-tip pens according to the picture above. Punch the eight holes of each template with an awl. You can now thread the wires through these templates, matching the colours; start with the black center wire. Cut the wires then to identical length, strip them, twist the eight ends together and solder them. Connect a 50 cm length of sturdy scrap wire. Slide the template from the connector end to the other end and carefully pull the wires through the tube, starting at the end with the connector shell. Once the wires are threaded, you can tear up the template, taking care to not damage any of the wires. Insert the black contact pieces into the connector shells and fix them with the tiny screws. Cut the twisted ends of the eight wires off and strip/tin them once more.

When using the tripod and any optional decorative elements, thread the wires protruding from the tube, then the tube itself, through the tripod adapter first, then through the other optional decoration(s), and then through the 6 mm hole in the display adapter assembly. Slide one more slot nut into the profile, insert an M4 set screw and guide this screw through the profile’s lateral hole. You can now fix the display adapter assembly on the aluminium tube in such a way that the display faces forward once the completed display stand is connected to the base. Tighten the set screw with moderate force in order to not distort the tube too much.

Do not shorten the protruding wire ends. In case something might go wrong you will be glad to have some extra length. Strip and tin them again and solder them to the display adapter PCBs, again according to the wiring table above. You can now bend them to loops and attach them in the slots to the aluminium profile using some adhesive tape in order to hide them.

Plug the displays to the display adapters, taking care that none of the pins are bent, then plug the completed display stands to the mounting base and fix them using the connectors’ coupling rings.

You’re almost finished now!

Summon up all the courage you have and plug the cable from the wall wart into your clock, then the wall wart to a mains outlet. If you have carefully followed the steps above, the displays should light up, and you can set the time with the three switches on the rear panel. It will look similar to my clock shown in the video clip below..

At the end of the day, I think my prototype meets the challenge successfully. When I showed Andreas the pictures, his comment was: 'This is exactly what I was dreaming of for the last twenty years'.

There are, however, some tiny flies in the ointment - but please don't tell him about them!

They are listed in the next step.

There are a few things that I am not too happy with:

1. The display stands are a bit wobbly, because the connector’s coupling rings leave a bit of slack. I will try to remedy this, either by working on the connectors or by finding some different connectors that are more mechanically stable (but also more expensive, for sure).
2. The USB-C socket on the break-out board isn’t sturdy enough for this application. I will try to attach it better using some hot glue. If that doesn’t help I will have to redo the rear panel with a barrel plug socket for connecting the wall wart.
3. The displays on the display adapter PCBs need a kind of cover, some small black boxes that I have not provided yet. These might be made simply from black cardboard, or perhaps using a 3D printer.
4. The contrast of the displays might be improved further by putting some light grey circular polarisation filter screens in front of them that would hide the unlighted, bright-grey segments from direct view.