Second February update.

February 17th, 2019

Not too much to say, it’s all in the film here on YouTube:

Basically I decided my keyboard design is terrible so I will rework it! The idea is to replace the bottom board with a PCB that the switches connect to in order to make the wiring far easier. It’s been a while since I done any PCB design so it might take me a while!

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3D printed Polish Enigma update.

February 3rd, 2019

I am slowly starting to get back into this project now. Need to get onto the wiring which is a massive job. I am making a little test jig with 26 red/green LEDs to help show where the current is going around the machine. I did a short film about it here:


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Demodex eyelash mites under the microscope.

January 3rd, 2019

A funny little film I made. You probably don’t want to watch if you don’t like the idea that there are things that live on you…


My eyes have been quite sore lately. Initially I put it down to hayfever but the sensation is more odd than that. More a kind of crawling, twitching sensation in my eye lids. They all look ok but felt funny. Like something was crawling about in the edges of my lashes.

Turns out something is…

I’d vaguely heard of these things before, small mites that live inside the bottom of your eyelashes. They are called Demodex Mites. So being a big geek I decided to pull out my microscope (an old Cooke, Troughton and Sims) and go mite hunting.


I tried pulling out a lash with some tweezers and accidentally managed to get two. So I put them on a slide with a drop of water and a cover slip then took a look through the scope. You can see the eyelash hair and the root.


And I found two mites! And yes, you can see them crawling about. The film isn’t great but gets better at the higher magnifications. I was simply holding my phone camera to the eye piece. Initial magnification was 24x, then to 60x then finally 240x. I should really 3D print some sort of adapter to make attaching the phone possible.

Once I am back at work next week I will go see my optometrist to see what can be done about it. Apparently they are quite common and I don’t think it’s anything to worry about. I wear Ortho K contact lenses so I am always very careful about keeping my eyes clean. The crawling sensation is really quite unpleasant but I feel better now knowing there really is something crawling about in there!

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Enigma machine pocket watch update.

December 18th, 2018

An update on the watch. I decided to make it into an actual watch. It was a comment on Hackaday saying they didn’t even care that it didn’t tell time…

Well, that got me thinking. Why couldn’t it? I spent so much time getting the Enigma machine part to work I never considered the watch part. So I did some investigation. Turns out there are many cool little RTC (Real Time Clock) ICs available that can talk to a micro that you use to set and get the time. The RTC runs independently from the micro with its own power supply and it keeps very accurate time. You set the time to it then it basically sits there and keeps counting the time up. Later on you can read back what the current time is.

You can buy modules to do this of course, like this one from Sparkfun. Or this from Adafruit. Both quite tiny by themselves but far to huge for my pocket watch. I did some hunting about and came across the STMicroelectronics RTC chips, one of which, the M41T62, comes with a built in crystal in a 8LCC package. That whole thing is tiny – 1.5mm by 3.2mm.

And they do free samples! So I ordered some. They are incredibly small.


All I had to do was solder 4 wires to it, power, ground and the two I2C wires. I managed that with 0.15mm wire after having stuck the chip to a popsicle stick with some wrapped over to make it double sided aluminium tape. That was to hold it in place as well as be a heatsink when soldering it. Then I had solder it using a jewellers loupe to see the bloody thing.


I then breadboarded it up to see that it would work with the Enigma hardware (using my damaged screen). You also need two pull up resistors for the I2C but I knew there was room for a couple of standard 1/4 ones.


Turns out space in side the watch physically wasn’t an issue at all. Space on the Arduino micro program wise was! I found a library for reading and writing to the chip using the wire library. It’s relatively simple. You simply read and write to registers on the chip. I found someones library to use but it was a bit messy and rather large and since I am only using the hours, minutes and seconds (so didn’t need to worry about any of the date or alarm functions) I just wrote my own simplified library with the functions I needed. The Arduino Pro Micro is pretty full:

Sketch uses 27,340 bytes (95%) of program storage space. Maximum is 28,672 bytes.
Global variables use 1,046 bytes (40%) of dynamic memory, leaving 1,514 bytes for local variables. Maximum is 2,560 bytes.


The RTC chip is wired direct across the battery. The current is less that 100uA, probably far less when the chip isn’t doing anything. On startup the Arduino in the watch reads the time from the RTC and displays the hours and minutes, in 24 hour time (it is a military device after all) in the bottom corners of the splash screen. It read it once then the internal Arduino clock handles updating the time on the display. You can manually change the time by holding the left and right buttons and clicking select. That simply increments the hours or minutes. When you hit the select button alone to exit the splash screen the time is saved back into the RTC if it has been changed.

And that’s pretty much it. Start up is instantaneous so the time is available as soon as you open the lid. It makes the device far more practical.

Putting it into the watch wasn’t too bad, just fiddly. I wrapped the chip and wires in some Kapton tape as strain relief on the wires themselves as the pads are so tiny any mechanical stress will rip them off. To sleeve the resistor legs I used a trick learned from plastic model making. You take a cotton bud with the hollow plastic tube and heat it over a lighter flame then when it starts to melt pull the ends apart. It stretches out into a thin tube. I then used that as small sleeving over the wires.

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And it all goes back together as before. I am not sure how accurate it will be. It should be fine given the batteries probably need replacing monthly and you need to reset the time then. If it is usable day to day I am perfectly happy with it. It doesn’t need to be hugely accurate. I am just pleased it is now practical and it’s name is accurate! It will be interesting to see 1, how well it keeps time in real use and 2, how long the batteries last!


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Enigma machine pocket watch.

December 2nd, 2018


This is a follow up project to the Enigma Machine Wrist Watch I made a few years ago.


I’ve been taking a break from my 3D printed Enigma machine as I am up to the tricky wiring stage. I have for years worn a pocket watch but unfortunately my last one got broken when it fell onto a tiled floor on an overseas trip. These days pocket watches are cheap and plentiful but the issue is finding people who can repair them. Even if you do it si so expensive it is not usually economically feasible. I often carry a little music player watch I made which you can see here.


I thought well, why not reuse the electronics and code from the Enigma wrist watch and put them into a pocket watch. The electronics and software are almost identical. I did upgrade from using an Arduino Pro Mini to an Arduino Pro Micro. I also added in better button debouncing using the bounce 2 library. The user interface on both watches is identical.

The first thing I had to do was find a suitable old watch case. A chunky one like the music player would have been good but I wanted what is called a hunter style watch. It is one with a little hinged lid on it. I ended up with a half hunter, one with a little window to show the hands.


The watch was a broken one so I didn’t feel bad about destroying a working watch. The case is gold plated. In the picture you can also see the little 0.96 inch OLED screen and the pro micro that is the main processor. You can also see how there isn’t much room available. The curved nature of the casing makes things tricky too of course.

The first thing I did was remove the window and etched a new plate to cover the hole. I did two, on in copper and one in brass to compare them. The design is based on the outline of an Enigma machine rotor. I used the brass one in the end.


I also bread-boarded up the circuit to make sure it was all still working and to play with battery configurations. I also tested using a bare bones Atmel chip but in the end decided the pro micro was the better way to go (and much easier to program since it has onboard USB).


One thought for batteries was using four button cells flat in the bottom of the watch but with only about 10mm of space to play with height wise there wasn’t room for the micro and stacked screen.

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The round shape means there is much less room available than in the rectangular wrist watch. I also thought about using a tiny LiPo battery like in the railway music player but I didn’t have any small enough and then you also have to provide a connection for the charger (or make the batter removable).

In the end I went for three button cells stacked, I am using LR54s which are only a few mm thick. I did thing of using LR44s lying side ways but the casing just isn’t thick enough to have room.

One thing with old watches like this is that they have two back covers, inside the back cover there is a second dust cover. I was able to use this as a way to clamp the circuit board for the watch in place. This watch casing is actually gold plated.

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It took an awful lot of prototyping and messing about with different configurations before coming up with the final arrangement. One of the initial thoughts was to put the buttons on the top plate which would be made from a PCB material. I used that method in the watch but the buttons on that are usually not seen. I wanted something cleaner for this so went with buttons on the base plate and little brass plungers that pass through the top plate to push them.

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3D printing parts to test the fit was invaluable.

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With the basic idea worked out I made the bottom circuit board. This is made from 0.5mm thick board to be thin enough to fit. I use the same method I used for etching the cover plate and the little brass Enigma logo. I print the design with a laser printer onto glossy magazine paper (Hornby railway magazines work well) then transfer the image to the very clean brass or circuit board. You use an iron on the highest non steam setting to heat the press the toner onto the metal. You can then soak it in water to remove the paper. A gentle scrub with an old toothbrush helps remove the paper.

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I then etch it in Ammonium Persulphate used for etching PCBs.

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The battery holder is a piece of brass tube I split so I could open it out. Inside it is a piece of clear acetate to insulate the inside wall. I etched the board so that the lower battery contact si a ring meaning if the batteries are put in upside down there is no electrical contact. This wasn’t strictly needed as the Arduino has reverse protection built in on the raw input pin.


Shown there is the first top plate I made from thin brass. In the end I needed to remake that from thicker material to allow the screen to fit down into it to give me enough room.

One thing I did have to do to save space was use very small switches. I went for the more tactile push buttons and am using a tiny NC plunger switch for the main power switch. The needed it’s plunger extended so the lid of the watch can turn the switch off. I used a piece of 1.6mm OD copper tube drilled out to 1.2mm and super glued it onto the switch plunger.

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I also turned up little brass standoff and tapped them 2mm  for the small screws I would use to hold the top cover on.

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I assembled everything on the base circuit board so the electronics of the watch and switches and batteries are one unit.

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The initial top cover was very thin but I remade it using thicker brass with a hole cut in it to locate the glass of the OLED screen. That let the screen circuit board sit up higher allowing more space inside the watch. I found I needed that because when I mocked everything up I forgot to allow space for the wires. Even using 0.4mm diameter wire made the electronics stack too thick to fit. By recessing the screen into the top plate I gained enough room.

Unfortunately you have to be very careful with the little LCD. I already had to cut it down a lot to get it to fit in the watch. But I wasn’t careful enough when assembling it during one of my mockups and I cracked off the corner of the glass. There must be tracks running through the corners as that made the display faulty.

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It was easy to replace and I also added some white glue under the glass to give it a little more strength.

I decided to paint the top plate wrinkle finish black like the housing of the wrist watch (and the top rotor cover of real Enigma machines). The trick to getting a nice finish si heat and my little toaster oven I found in an op shop worked perfectly. I also used it to bake on the red paint I back filled the little brass Enigma badge with.

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Another issue I found after assembling everything was that the buttons for the left and right switch were’t 100% reliable. They would get into positions where they would stick. This is because the button is not directly under the plungers.


This is because the buttons couldn’t be too close to the walls of the inside of the casing. In the end I made buttons with fatter bases and then had to file clearance into the casing to allow space for them.

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That fixed the problem. Assembling the watch isn’t too hard. You fit in in from the back and the inner back cover clamps the board in place. You then drop the top plate on. The buttons are held in place temporarily using Kapton tape.

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Two brass screws hold it on, one doubling up as the battery negative terminal holder. That is made from a piece of springy bronze taken from an old WW2 piece of radio gear. So the watch does have a little bit of WW2 in it!

The pro micro seems faster to start up faster than the pro mini (faster bootloader?) so the watch turns on and is ready displaying the splash screen by the top you have lifted the cover. I am very pleased with how it looks and functions. Battery life won’t be great of course, maybe 2 hours continuous use. But that’s plenty for a (100% functional) novelty watch. It has a nice weight to it as well, weighing 90 grams without the chain.

And finally more pictures of it finished and next to the wrist watch.

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I made a film showing how it is assembled here:

And this is the previous one with the wrist watch showing how the interface works:


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