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Yet another narcissistic load of old cobblers that no-one will ever read.

The Christmas Clock

In our road, we have an annual advent calendar where alloted households display a number in a chosen window and on that December date unveil an illuminated, Christmassy display. We were allocated 14 and Elspeth suggested a clock face with a mouse staring up at it...

Twas the night before Christmas, when all through the house
Not a creature was stirring, not even a mouse;
etc.

This is an account, perhaps a bit laboured, of how the clock was made.

Clock Face

The first thing to do was to track down a clock mechanism with some big hands as that would dictate the size of the clock face.

The next task was finding an image I could use for the clock face numbers. I found one with a Google image search and removed the hands from it using Paint.Net (a very good and free image editor for Windows). I needed to blow the image up without it getting all blocky and pixelated so I used an online tool to convert it to a vector (.SVG) file.

clock-face

I still needed to print it out to the correct size but I decided to wait until the 750 mm diameter acrylic (Perspex) sheet I ordered arrived. This was the expensive part!

I tried using Word to print the enlarged face but that didn't work too well. In the end I used Big Print (https://woodgears.ca/bigprint/) which was exactly what was needed since it allows to you to print it out on several A4 sheets which when stuck together come out at exactly the size you want. After trimming the margins off and taping it all together I was able to check that it matched the acrylic disc. Bingo. First try.

Body of the Clock

I planned to use either thin MDF or hardboard for the back. A visit to B&Q revealed they had white-faced hardboard, which was cheap and would save me some white paint so that decided my choice. Unfortuately they don't sell it big enough to cover the 750 mm face - so I had to fix two pieces together with a wooden batten. The plus side of this was that it provided some stiffening and a solid(ish) part to hang the complete assembly by.

The hardboard back and acrylic face were fixed together with M4 x 20 mm nylon spacers and M4 nylon screws. Acrylic is easy to drill but also very easy to crack! It's normal to drill smaller pilot holes first and/or use a centre-punch for accurate positioning - but both of these will result in cracked and broken part though if you're using acrylic sheet.

Lights

Of coursre the clock needs to light up; it'd be a poor do if it didn't. You can get these 12 V LED strips fairly readily on Ebay and other online retailers. I calculated I needed just over 2 metres for the outer ring of lights and possibly another couple of concentric rings of lights for the rest of the face. I went for four rings of lights in the end since I had them!

When I connected it up for the first time, the individual lights were discernable, which I'd feared and didn't want. I considered putting a layer of greaseproof paper between the lights and the face to diffuse the light more but settled on increasing the distance between the front and the back by adding another set of nylon spacers, giving 40 mm between the face and the lights. Not perfesct but definitely better. (The photo below is from before I sdded the extra spacers.)

Wiring Woes

Let's be clear, I suck at soldering. It's not that hard but it does require a level of good eyesight, steady hand, patience and skill that I'm not sure I posess. Either way, I managed solder up the connections and all seemed well. These lights have individual red, green and blue LEDs in them and you can connect a controller that lets you adjust the colour and even exhibit a variety of flashing effects. However, at this point I noticed and red and green seemed to be short-circuited together. It must've been late in the day becuase I decided I didn't care - as long as I could independently adjust the level of blueness, which I still could. I also noticed that the 5 Amp transformer I was using was getting pretty toasty - but by my calculations, 5 Amps should be (just) enough. Hmmm...

Finishing off and Installation

The last step was covering the sides so all the light didn't spill out. I wondered about gaffer tape but it wasn't quite wide enough and not very substantial. Elspeth suggested the cardboard you get left over in the middle of rolls of wrapping paper which by amazing serendipity, we have lying around at the moment, for some reason! This was a stroke of genius and worked well. I added a layer of gaffer tape over that too - for good measure - and to make it black. It was at this point, after the innards were all sealed in with tape and cardboard, that the green LEDs all seemed to fail. Sod it...

Another day. I cut off a lot of tape, prised off the back and fixed my shoddy soldering. I also concluded that the LED controller was dodgy since the green LEDs were still a problem and so I twisted the red, green and blue wires all together and ditched the controller!

The reasssembled clock was installed in the designated window early on the 14th Dec (our alloted advent date) and it worked resplendently - for about 30 minutes until the power supply overheated and took out all of the downstairs lights. This required a rummage in the garage for a bigger transformer and a few minutes later a 20 Amp beast was installed (pictured in true Heath Robinson style.)

I'm in no hurry to do this again but next time (!) I should try making the numbers with a laser cutter or a CNC router. Perhaps...

Update - I can now confirm that the 5 Amp power supply is officilly fried! And that so far the 20 Amp one is running cool and has not yet burned the house down. Which is nice.

Comments (1) -

  • Mum

    12/14/2021 5:16:15 PM |

    Wow! That's brilliant.  Very clever.
    X

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