Intro: The White Rabbit Nixie Clock
As you can tell from my prior postings, I have a fascination with Nixie tubes, their history, how they operate and the unique look and light they give off, I was lucky enough to have access to aN Epilog laser cutter for this project and now understand how powerful and flexible tool it is for an engineer and artist.
Due to the nature and lifespan of a nixie, I wanted to design a housing which will allow the owner to close it and de energize the 6 time telling Nixie’s, allowing for a longer life of the Nixie tubes.
I started by using a cardboard pattern of all of the components to make up the mechanical moving components, after moving th pivots around to get the most efficient movement without strain or collision I decided the order of the components and the distances of their shared connections to allow parts to move within or round others without conflict.
I made a laser cut prototype of an early version for testing, my early version was to be operated by two servos, one for each side that work together to open the cover. I later opted to Make this a manually operated featured by pushing a bar down to open then closing the top by pushing it closed, I chose this route because it got rid of two servo that would require to be powered and may buzz when open or closed.
I started with cardboard, made 2-3 prototypes of the moving components, marking all the component with issues that needed adjustment, then ordered 0.125” walnut planking from ebay, the actual thickness of the wood was 0.130”, so some minor adjustments had to be made to slots in the parts. I also ordered assorted packs of wood in different thicknesses. Other than wood I used thick and thin cyanoacrilate with its kicker. I ordered hardware from McMaster Carr.
Just a quick note, I design for a living and tend to convey more information through imagery so there will be plenty of information in both the text and photo portions of my instructable.
I have tried to cover all angles of the build in every aspect I can think of, thanks for taking the time to look through it.
Step 1: PROTOTYPING
After making my cardboard model and finding satisfying points for movement, I noted the parts, their orders, how and at which points they articulated in relation to each other and the order of the stack.
I started modeling the whole clock in solidworks, all components were to be wood, grain direction and type of wood is very important to the function of all the parts, most importantly the mechanical parts that had to move and take the stress of the mass and movement.
Solidworks allowed me to simulate the opening and closing of the covers, I could move pivot points on the assemblies to make the movement smoothe and unhindered. I spent the majority of my time figuring out the Nixie carriage rotation and tie in to the covers.
I went through a couple of more prototypes until I reached the final version of what was to be made of wood, there was a few potential issues with prototyping in acrylic which was .125" thick for the end material which would be .130" so for tolerance checks I kept in mind the .005 difference.
Plenty of parts were generated, many went into the obsolete folder, I narrowed it down to a group of parts then started playing with their connections, their pivot points, shifting them and seeing how the entire assembly moved.
sometimes they would bind up and other times the motion would offset parts, twist them in weird orientations. their is also a ratio that had to be worked out, swinging a lever 20 degrees giving your output a 90 degree motion.
after a short while i was confident enough to cut an acrylic version of one of the opening sides (red acrylic version) after reviewing and making modifications, drawing on the actual assembly help me remember the issues, many having to do with hardware clearing moving links, I cut a second the clear version ( see the step prior to this one for pictures).
Step 2: COVERS
Majority of the flat components are dark walnut planks, the mechanicals mainly consist of components made of Cocobolo and the remainder is a mix of maple, African Paduk, cherry, russian ply and spruce, sizes are .125" and .25" in thickness.
The covers consist of five parts, as shown. The parts were laser cut with relief holes that I experimented with, the dark walnut was .130” thick and did not like to flex, so cutting these openings and steaming the wood will give me the curves I need in this material, I boiled water in a kettle, suspended the parts over the bottom of a smaller pan, poured in the water and covered the whole thing with a bigger pan sealing the steam inside. After a few minutes I would pull the parts out carefully flex the parts and steam them again, I repeated this process about 4 times then strapped the pliable wood to a tube after checking the curves against the clock surfaces.
After cooling, the parts somewhat held their shapes, I found tubes of various diameters and either strapped the parts to the outsides of insides of the tubes.
I wanted to inlay some light wood within the dark, so I used the same cut file for the Dark walnut covers, and cut another set in a light spruce or maple sheet. After the walnut covers were steamed and bent I started installing the cutouts of the lighter wood, the walnut equivalent of these light wood pieces were discarded for flexibility, now that the wood retains its shape inserting these in the openings and gluing them from behind made the dark walnut pieces look really good, so I proceeded in duplicating the process for the two lower and two upper cover front and back. I gave the pieces a light sanding then in a later step I masked the fronts and painted the insides a matt black.
The Rabbit, I wanted to make the ends more dimensional so they stand out, so I traced the outlines of the rabbit head and tail onto a beautiful piece of figured maple, a piece left over from my first instructable, using a bandsaw, I rough cut the outline of the parts and proceeded to shape then on a belt sander, after a short time i had the profiles that nested together and looked good when I mounted them to the clock assembly, I made sure that when the Rabbit was seated the part below the "ears" nested on its back, after testing I removed the components and proceeded to give them a couple of coats of clear lacquer.
Step 3: NIXIE TUBES AND CARRIAGE
The tubes are tall and need to lay forward when stowed, so finding the correct pivot axis and linkage which ties the tube assembly to the opening cover was important to make this all work, using solid works, I was able to shift the axis and the connecting linkage around virtually to find the optimum positions for both. Remembering that this assembly has to rotate 90 degrees and drag about 20 wires with it.
The six nixies in my project are Russian made IN-18.2.
I found some circuit boards on eBay for mounting the Nixie tubes, I made a tube spacer out of EMA tubing and a hemisphere, I lined up the height I wanted the tube to stick out of the carriage, marked the depth then attached the hemisphere to the tube before dropping the marked nixie into it and seeing how much has to be removed to get a consistent spacing between nixie and its circuit board, this insured that the Nixie’s are all soldered at the same distance from the circuit board, this distance allowed for the digit to clear the carriage assembly and allow room beneath for the 3 mm blue led. I checked alignment then proceeded in soldering the Nixie’s using the spacer tube. I tested their fit in the carriage, when I start wiring, a mistake I made was not wiring while the tubes were in the carriage assembly, I used a wire guide to strip my wires, to keep it consistent but silicone is flexible and some wires ended up tight so I wicked all the solder and started over. solder while the nixies are mounted allowed me to create accurate lengths to each pole on every nixie, reducing extra wire that could get in the way.
I ended up soldering and wicking twice, completely rewiring the tubes, My first go taught me that silicone has fat insulation and the tubes not being mounted in place caused some strands to be tight. i was using 24 awg silicone insulated wire.
my second go was 28 awg silicone insulated wire, this time with nixies mounted. I noticed the thick insulation took up a lot of lateral space, this was a problem because this assembly rotates so I wicked all the solder up and started again.
My third go was with 28 awg ribbon cable, this worked out as the strands are thin, I ended wulling the wires apart so i can group them tighter and it worked out really well.
I later went in and arranged the wires with tweezers so they sit as flat as possible.
Step 4: Electronics
A word of warning before proceeding....
DANGER: The clock pcb includes a switched-mode voltage booster circuit. This generates nominally 170 Volts DC, but is capable of generating up to 300 Volts before adjustment. Assembly may only be undertaken by individuals who are suitably qualified and experienced in electronics assembly, and are familiar with safe procedures for working with high voltages. If in doubt, refer to a suitably qualified engineer before proceeding
The voltages generated by this circuit can give a potentially LETHAL ELECTRIC SHOCK.
This is not a finished product, and the person assembling the kit is responsible for ensuring that the finished product complies with any applicable local regulations governing electrical equipment, eg. UL, CE, VDE.
Pete from PV Electronics supplies me with all my nixie needs, to my knowledge he is the only producer of the nixie prototyper board specially made for artists and engineers, allows you to remotely mount your tubes and connect them via terminal blocks. you can find him here https://www.pvelectronics.co.uk/ . I’m not going to show the assembly of the board as that’s another instructable in itself and I had an assembled dink circuit board lying around and wanted to use it for this clock, I contacted him about shutting the tubes off and on but still keep time, He sent me a picture diagram (see pictures) of how to achieve this using a switch a diode and a connection to one of the boards IC's.
The circuit board is mounted on the bottom plate that has nylon standoffs keeping the solder points off the wood, slots in this bottom plate accommodate the vertical back plate with the button, led and power port openings. this backplate gets trapped between the two sides, top and bottom plates, I sanded down the tabs on the bottom plate sides so should I need to gain access to the main card, I would just need to loosen the side assemblies and drop the board and bottom plate out. The Wires I chose to use very soft flexible silicone covered 28awg wire to all the nixie plates. this will allow for less strain on the nixie carriage when it rotates.
the power supplied to the "show LED's" is 12v, using an online resistor calculator you can easily figure out the resistor values yo need and some will give you a schematic to make life easier... you can browse for leds here...
and just a couple of random calculators here...
if you do decide to use the premade nixie boards from ebay, the board comes with pin connectors and blue leds, you can find the boards here...
I have a schematic of the led/resistor layout I went with in the pictures above... I went with two 120 ohm resistors colored brown/red/brown and gold.
It's very important to keep track of wiring colors and the associated numbers, in this situation the numerals are all wired in series, the anode wires are separated, hour hour, minute minute, second second.
I started to figure out where the micro switch should go, so using tweezers holding the switch I cycled the carriage and held the switch in various locations trying to see where the best place was to place it so carriage presses on it when full open. this will turn the tubes on , when the rote closed the switch is released and the tubes go to sleep.
Step 5: Opening Mechanism
As stated, I started out planning to use two servos to operate the opening and closing of the lid. I chose to make this an operation that involves pushing a lever spanning the width, down to raise the cover and rotate the tubes.
Clock was named the white rabbit because the side resemble a white rabbit in a standing and sitting position (see last picture), there is a center cam that connects and pivots about the center common axle, followed by another walnut disc spacer, and the opening lever, two linkages span from it, one to the rear cover and the other to a curved pivoting control arm that in turn rotates a triangular piece that has the mid and front cover pivoting off of it. it's a complicated movement of the components. I will try and add a video of it opening, so far I have had no luck so I may end up showing a sequence of pictures showing the opening. click through the pictures, I will try and clarify all this a little more...
using the correct wood and grain direction for the end purpose is very important, some parts take take on a mechanical load when opening and a piece in the mechanical assembly taking pressure the wrong way will snap, I showed in a previous step, how soaking the wooden part in cyanoacrylate thin, letting it soak and set, then sanding it back to its correct size reinforces the wood, you may have to re-tap the holes in the pieces after this process.
Step 6: Testing and Cover Plates
now we come to the fun part, two shoulder bolts on each ends of the Nixie carriage act as it’s pivots, the carriage rotate’s 90 degrees forward on these shafts, said shafts pass through two sets of bearings on each side and fasten to the first of the side plates, using dense wood like cocobolo allows for drilling and tapping, I use a small drop of cyanoacrilate glue and drive the threaded end of the shoulder screw in, let it set and unscrew, the glue strengthens the threaded holes and acts as lock-tite would, it holds on tight to the threaded end and does not allow it to work itself free during its cycling.
A long slot in the base top allows for the wire harness to stow during carriage rotation, getting the harness nice and tight against the carriage can prove difficult but it works. I found after testing that separating the strands in the ribbon makes it easier to make the harness compact and more flexible.
First I had to remove all the Nixie’s from the carriage as the shoulder bolts cannot be installed due to their length. I reinstalled then temporarily after running the bolts through the base vertical supports, I tested the rotation making sure nixies were clear of everything when carriage was in the open and closed positions, then removed the tubes again as the shoulder bolt cannot be fastened with the tubes in place.
I placed the carriage in position between the two base verticals mounts, and pass the shoulder bolts through the verticals, shims and bearings into the first side plates, I checked to see if the carriage rotates smoothly without interference. Then attach the standalone side opening assemblies, the base plate itself has two flat tabs on both ends, one narrow and one wide, these tabs are used for alignment for all parts to be mounted on either side, wide and narrow slots have been cut into the assemblies, so nothing can be installed backwards. some bolts cannot be tightened down as they inhibit free movement so use cyanoacrylate with a thin nozzles so you only apply it where you need it and not fuse moving assemblies.
After the shoulder bolts are in and the carriage assembly swings freely, the tubes can be re-installed for the final time while the carriage is in the tilted forward, giving you access from the bottom of the carriage, covers cannot be on for this step.
base cover went on first, then the top front and rear covers, and last was the top flex cover.
Be sure to test run your nixie clock at every step, it’s going to be easier to fix a broken wire early in the assembly than later.
Step 7: FINAL ASSEMBLY
The final components left to go on are the mechanism side covers, levers and the push bar.
the covers keeps objects out of the workings of the opening mechanism, there is another plate above this that limits the lever movement, essentially it has a cutout of the levers movement extremes, all of these plates sandwich together with a series of socket head 2-56 screws and some spacers between the limit plate and the outer finish plate, life is easier if you make a sub assembly of the outer cover pieces.
The (7) 2-56 SHCS (socket head cap screws) are mounted through the outer plate, 7 spacers are sandwiched between it and the limit plate, trapping the spacers. this sub assembly can then be mounted over the mounted lever. fasten the hardware and then on to the other side.
I found some slightly tarnished square brass stock, I used an abrasive pad to give these tubes a light brushed look then gave them a light coat of lacquer to keep them polished. the levers are made of two parts, the long body of the lever and a smaller end piece that gets fastened to the long lever after the bares are set in place, both parts have the same square holes in them, the difference is a small offset of the square cut outs on the smaller piece, bars move free through both parts when they are not screwed together, after setting bar positions the smaller component of the lever gets tightened, the offset applies pressure and locks the tube in place without glue.
I had to add two brass knobs on the sides as the clock has very little weight and these knobs allow you to use the knobs to press against instead of relying on the clocks mass on a surface.
I cycled the clock and it worked fine, the wire does cause minor strain but it rotates fine, it creaks a little during the move, one other issue was the front corner of the nixie carriage tripping the micro switch when rotating open, so the numeral are off when closed, during the rotation the front corner of the carriage taps the micro switch flashing the digits a split second before they come on for the open position, this was solved by shaving the underside of the front carriage a part not visible.
the clock operates well, there are 25 or so features to the clock, I love the digits fading, the lotto roll (all numerals cycle for a short period at set intervals) and having a zero visible instead of a blank on the hour set of nixies.
Hope you found this informative and inspiring.
thanks for hanging in there...
Runner Up in the
Epilog Challenge 9