My collection of home projects.
"Just for the fun of it"
Friday 7 April 2023
3D Printed - Modular - Kitchen Utensils - System.
I got a little tired of the mess in one of my kitchen drawers, so I started 3D printing a modular "tool holder".
The tools are all designed in Open SCAD, so basically consists of cylinders, and cubes.
I started with the holder for my mixer tools, as they always got tangled up. As that turned out to be a success, I continued with the rest of the kitchen tools I use most. Notice the prominent spot for cork-screw.
On the latter photo you can see the dove-tail connection between each module. The spool holder includes a little knife to cut the thread. Costs for the hole system - less than 1 euro in materials and hours and hours of fun designing each module.
Maybe the most used tool was a little tricky because of the curves.
This is where it started. The most useful of them all
And the companion tool. A foil cutter and rubber cork. I got the set as a goodbye present from the last company I worked for in Denmark all the way back in 1998. It's of course Danish Design.
Most of the tool holders has been created from simple shapes as cylinders and cubes.
For the Garlic press I used an other method. I took a photo of the presser and imported it into Open-SCAD. Saved a lot of time to do it this way because of the odd shape.
The spool holder was probably the most fun to make.
This mainly because I wanted to include a knife to cut the thread.
The knife is just a piece of steel from a can of some sort. Probably canned tomatoes.
To create the knife blade I just made a small cut with my wire cutters and bend it a little to allow the threat to enter between the two sharp edged.
This holder is currently a bit of a failure. The fit is bad and the whiskers won't stay put. Luckily it's just one module - I can replace it with a new better version, or maybe for an other tool.
These two holders I just made because I felt I wanted to. The both turned out much better than expected.
Thursday 16 February 2023
From Idea through Theory to Reality
For quite some time I wanted to make a bathroom cabinet, but never really got around to do it. I could of course have taken the easy way out by going to IKEA and buy a flat-pack. Though I'm Scandinavian, I'm not really an IKEA kind of guy. It's all a little to square for my taste.
I finally got the finger out - So I fired up AutoCAD and started designing a bathroom cabinet that fitted my quirky taste.
To be clear - I'm neither a designer, nor a vizard when it comes to creating 3D renderings, but I do enjoy the process of creating and building - and I have a lot of fun doing it. Isn't that the most important thing?
The cabinet as rendered in AutoCAD
And the reality. Just needs a lick of paint so it can handle the bathroom environment.
Errors were made, struggles was fought, frustration ran high at curtain moments. Building the curved doors was probably the bigger challenge.
I don't own a lot of woodworking tools and I do all the building work in my living room, so I decided to use GAMMA's woodcutting service for some of the wood. They did a brilliant job. The wood was cut precise and had a very nice finish.
To help me getting through the build I bought myself a new Jigsaw - that was a lifesaver as I needed quite a few curved pieces of wood - and GAMMA's service is still quite limited in what they can make.
The cabinet is build from 3 mm multiplex for the sides and doors. 9 mm multiplex for the bottom, shelf and top. The inner construction is made from 27 * 27 mm pinewood.
The idea was to bend the multiplex for the doors around some curved pieces of pinewood, but the 3 mm multiples was quite a bit more stiff than I had expected, so I had to give up on that. Fortunately I did have some 2 mm birch multiplex from an other old project and there was just enough for the doors. The did result in two different wood types (as can also be seen in the photo above) Also, because the birchwood was thinner (only by 1 mm) I did have to make some minor adjustments here and there.
because of the two different wood types, I'm probably going to paint the sides plain white and leave the doors with clear coating so you can see the birchwood finish.
The following is just a bunch of snap-shots taken during the build.
The "skeleton" is done. That was the easy part.
The cutout for the sink took quite some measuring. I did 3D printed a helping tool to transfer the shape of the sink. That removed some of the guesswork and I could finally get to use my new Jigsaw.
The shelf was easy finished using the Jigsaw.
The framework for the first door is ready.
Starting to clue up the door, this was the easy part.
Continuing the glue up. I had to do this in small steps as I didn't have enough clamps to do it in one go.
The first door is ready.
The second door went a little more smoothly than the first. Mainly because I learnt from the mistaken made on the first.
Both doors are ready - and a still have all me fingers (and a few splinters)
View from the back. Nearly looks like a chair from the 1930's. Maybe that could be my next project...
The, nearly finished, cabinet. It fits in the allocated spot with only a few millimeters to spare. Next step. Going the whole lot with filler and sanding it down to prepare it for painting.
Sunday 15 January 2023
Upgrade Power Supply with Fan Cooling.
After a bunch of years - in the middle of a long running 3D print, my printer suddenly stopped. The bed fell to the ground, well the base of the printer, with a bang.
My first thought was - Oh crap. Now I need a new 3D printer and can't really afford it at the moment. After the initial panic went away, my second thought was - Maybe it is only the power supply, a little optimism newer hurts. So I measured the output voltage of the power supply and got nada.
So I went shopping for a replacement. The specifications of the old power supply was: 12V / 5.3A.
Although I normally go to Conrad.nl for that kind of shopping, I was not able to find any good replacement. The search functionality at Conrad.nl really sucks. So I went to Bol.com and found a 12V / 6A replacement. Well a little more power couldn't hurt, so I ordered the power supply.
The new power supply was delivered next very day and of course had to be tested, so I found a simple object to print.
To my big disappointment my 3D printer stopped again after about an hour of printing. Damn - Maybe it was not only the power supply that had failed after all. When picking up the power supply to check the connections, it was hot as Hell, so it had obviously over heated and shut down.
It's of course good the the power supply have thermal shut down, but it should be able to run continuously at its max ratings.
I tried to let the power supply cool down and did another test print. This time it finished without issues, but the power supply was again way too hot.
So though the specifications for the power supply was on the good side and the Bol.com site stated that the supply should be usable for 3D printers, the closed enclosure, without any air vents, caused it to over heat. Not very handy for a 3D printer supply that is supposed to be able to run continuously for several hours or sometimes even days .
Because the power supply "only" gave up on long running prints, I decided to try to add some active cooling to the supply.
Getting the case open was a little bit of an issue. I thought it was one of these thermo clued cases thar are impossible to open - so I went for my hack saw and gingerly started to hack the case open. Got in - and realised that the case was clipped together not glues. Well too late and I was in.
There were 3 very small cooling fins. One glued to the top of the output transformer. One on the input MOS-FET and the last one, the smallest, on the output rectifier diode.
It was the cooling fin on the output rectifier diode that got very hot.
Fortunately I had a small 12V fan in stock, so I could easily attach that to the sower supply. The fan I'm using is 40 * 40 * 10 mm and is very quiet. So I went ahead and installed the fan on the now somewhat molested original case. Some hot glue and masking tape made that an easy job. Not a looker, but enough for testing.
The somewhat molested power supply held together with hot glue and masking tape.
As the original case was now in a very poor condition I went ahead and designed a new case in OpenScad. The dimensions of the new case is only slightly larger than the original one, though a little taller. I placed the fan close to the overheating diode, and the air outlet as close to the coldest part of the power supply. That way, with some luck, all warm components would get some airflow.
Printing the case took a couple of hours. The power supply barely got hand warm now. So the little fan did its work. Quite a good result for such a small fan - and very sketchy set-up.
OpenScad model of the new power supply case.
Another OpenScad view of the case.
The new case is just a little larger than the old one.
The finished case looks good and works great. I had a few issues with the tolerances, but fixed that with a little bit of sanding. I regret I didn't install a power switch on the case, as I don't want the fan to run 24/7. Luckily I can print an upgrade in an hours time. So when I get a switch ordered I will fix that.
The last few years I have begun to make home made presents for my family. Mainly small boxes made from wood, but more recently also 3D printed objects.
I know that only children are supposed to make home made gifts. Though I'm quite grown up now - my sole is still a big child, so I allow my self to continue making home made gifts.
I needed a Christmas present for my sister in law and was a little lost for ideas. I also wanted my sister in law to get a home made present but as mentioned I didn't really have a good idea.
Fortunately one of my favourite You Tubers (Big Clive) made a video about some floating candles.
When I watch the video I thought that it could become a nice little project to make my self - and at the same time I had a Christmas present idea for my sister in law.
The 3D print
I create most of my 3D models in a the free program OpenScad. In OpenScad you don't draw your objects directly, you build them from simple objects as spheres, cylinders and cubes. It a little bit like programming your objects.
When designing the 3D model I initially had great difficulties figuring out how the switch the candle on and off. Also making it easy to replace the battery was a bit of a challenge. Even connecting the battery caused me some headache. After quite a few trail and errors I came up with a "screw to turn on and off" design. I split the candle in two halves with a thread.
That way I solved two problems in one go.
The switch is mounted at the end of the circuit board and gets turned on by screwing the candle tight.
To switch the candle off, turn the candle 'open' a couple of turns. In this way I could avoid having the switch visible. To replace the battery simply screw the candle fully apart.
Initially I wanted to print the flame my self, but the result was a little sad looking. As I had bought a bunch of LED Tea candles, for experimenting already, I decided to use the frame from them. The only modification I needed was to make a small hole for the hanging wire. The flame even had mounting tags so it not only simplified my 3D design, it worked perfect.
The circuit
I wanted the candle to be powered by a single 1.5V battery (AA/Penlight). I also wanted the circuit to be simple and not using any special components.
The Candle LED I'm using requires 3.2 Volt to work so getting the LED to work from a 1.5V battery required some sort of 'step up' circuit. There exists countless ways to step up a voltage. They often require some special IC or chip to get working.
As I was a little in a hurry to get my project ready before Christmas, ordering components from China was not really an option. Furthermore, when ordering components from China, you don't always get what you ordered and the quality can be questionable.
So I wanted a circuit I could build from of the shelf components. I again turned to Big Clive. He has a great video about a small simple circuit called a Joule Thief.
Where normal battery operated equipment, such as your remote control, stops working when the battery voltage drops below 1.0 - 1.2 Volts, the Joule Thief will 'suck' energy out of the battery to as low as 0.6 - 0.7 Volts. So when the batteries in remote control gives up - you can use them in a Joule Thief and get quite a few extra hours out of them.
The basic version of the Joule Thief only requires a very few, of the shelf, components.
A general purpose transistor T1, a current limiting resistor R1, a small hand wound transformer TR1 and of course a LED. As I'm using a Candle LED I have added a few components - a diode D1 and a smoothing capacitor C1. In the design I also added a 3.2V Zener diode D2, but it turned out that it is not needed.
To prolonge the battery life even further I have added an extra current limiting resistor for the LED (Not shown in the circuit below.)
The modified Joule Thief
To make the circuit board as compact as possible I decided to use SMD (Surface Mount Device) components. Though they can quite difficult to work with, specially when ones eye sight start to diminish, it is very satisfying to see the end result. The issue I had connecting the battery to the circuit board (I initially wanted to use an of the shelf battery holder) I solved by using battery clips I could mount on the circuit board.
Fully assembled circuit board.
As mentioned earlier, I had to get my components quite fast, so I ordered my components by Conrad. Generally the quality is alright, but also quite a bit more expensive than China.
When searching for Candle LEDs, I only found one type. The review for the LEDs was not great. They should be a little "too wild". I decided to buy a small amount anyway, just to check my self.
The only alternative I could find was ready made Candle LED Tea candles. So I ordered a bunch of those too. Conrad tried to convince me to buy batteries too, but I was only interested in the LED so I didn't bother to order any batteries. When the order came through a fe days later, it turned out that the candles was delivered wit batteries. I can probably use a couple in my kitchen scales.
When comparing the two LED types, the of the shelf version flickers quite a bit. Something like a candle in a window-seal. The ready made version is much more quiet, barely any flicker. I guess it's a matter of taste, but I prefer the ones with more flicker.
The off the shelf LED does seem to dim faster as the battery wears out. I still need to test this better though.
Sunday 10 January 2021
3D Printed Van de Graaff Generator.
"Artistic" impression of my 3D printed Van de Graaff generator.
My small 3D printed Van de Graaff generator.
How does a Van de Graaff generator work?:
I will not explain how a Van de Graaff generator works in this blog entry.
I will, here and there, pop in some technical stuff if it can help explain things else I will rely on a few images.
One point I will highlight here though.
Don't confuse a Van de Graaff generator with a Tesla Coil. It is two quite different beasts. A Tesla Coil works with high frequency, quite often using powerful high voltage neon transformers. A Tesla Coil will, if it works good, deliver continuous sparks that probably will destroy any electronic equipment in the area.
A Van de Graaff generator is a much more "gentle" beast. It builds up the charge, assisted by the rubber belt and charge supply. That means the sparks only fly when enough charge has been build up. The faster the belt runs the faster the charge can be build up.
As this is 3D printed plastic parts you should not go over board when choosing your motor and drive wheels.
Warning:
This Van de Graaff generator uses a very high voltage non insulated Ion generator for the charger source. ~5kV
Some parts of the Ion generator are referenced to 240V~ so no touching those parts.
The top sphere is well insulated from the 240V~ so no electrocution risk - but it will still give you quite a nice zap if you are in to that - If you are reading this post you probably are... I have achieved sparks up to 40 mm (1.5 inch) Looks great in a darkened room - not as in the image above, wouldn't that be great.
Build at own risk and only if you know what you are doing.
3D Printing:
I will not explain a lot about 3D printing in general.
Firstly - I'm self still quite a novice when it comes to 3D printing.
Secondly - Every 3D printer is different, so what might work on my printer, might not work for you. Thirdly - There are loads of other pages and videos on the web with tips, tricks and tutorials.
Instead you can download the free OpenScad programme and all the source files from my Thingiverse page. That means that you can change the design after your own wishes. With OpenScad you can create your own .stl files.
So now we got that out of the way...
I have always wanted to own a Van de Graaff generator. We had a fairy large one at the school I went to and fortunately I was sometimes allowed to "play with it" after school hours.
To build my own version have been on my mind more times than I can count - but it have newer come to more than a bunch of drawings and some small experiments.
The biggest problem building a Van de Graaff generator is the metal top sphere. Without any proper tools it is close to impossible - until I got myself a 3D printer. I thought so at least.
I have actually had my 3D printer for quite a few years but I have never been able to get any good results with neither it or the software that came with it. Only the "demo" objects that came with the printer came out perfect. What ever I tried to create and print, came out as - sorry for the expression - bird shit.
I tried every possible setting, both recommended and experimental. Nothing worked.
So the printer stayed in a corner of my flat with a cover over it for a year or two. Then some time ago I wanted to give the printer an extra go. I knew that it could print properly, the demo objects, so it must be a matter of the self generated files. I decided to do some proper testing and experimenting. I ended up writing a C# programme that translated all G-Code parameter to "proper" values. Very experimental but I was finally able to get some quite acceptable results. Unfortunately, after finally being able to start on a few of the projects that had been waiting in the background, I realised that the printer had a mechanical misalignment. One that I could not fix - and as the warranty on the printer in the meantime had expired, I had to find another solution.
Fortunately the misalignment was only on the X axis - so I added an "anti-misalignment" procedure to my C# programme.
Now finally I could get started on my long waiting childhood dream project. The Van de Graaff generator.
Well - so I thought. There was still quite a few issues to overcome. A few smaller;
The size of my 3D printer (150 * 150 * 150 mm).
The design of the rollers - one metallic and one non conductive.
The rubber belt that carries the high voltage charge to the sphere.
How to drive the generator. Belt driven or with gears - Motor or hand driven.
What motor to use if any.
but the biggest challenge was still that metal sphere.
Other stuff that needed some brain activity;
Power supply for motor.
Power supply for charge injection.
Safety!
and lots of stuff I didn't think about until I ran into whatever issue it was.
And one important thing - I didn't want to spend excessive amounts of money on this project.
A few things I had to get hold of, but that was mainly stuff I would normally have in stock anyway, or at least would be handy to have in stock.
Most non 3D printed parts though, are stuff I had laying around - so recycling at its best.
Size matters
The issue with the size of my 3D printer, I solved by thinking back to my birth country - Denmark- and my childhood favourite toy - LEGO.
I grew up just half an hours drive from Billund but have actually only been in LEGO Land 3 or 4 times. I didn't solved the size issue by printing LEGO blocks but by printing smaller parts that could either be screwed or clicked (the LEGO inspiration) together. I ended up using a mix of small bolts and some clickable parts.
How high can we go.
I ended up splitting the frame of the Van de Graaff generator in tree parts. With that I could get a reasonable height without too many joints and still create a sturdy frame. I ended up with a total height of just around 30 cm (12 inch) so each part ~10 cm (~4 inch)
The frame parts
The base
I initially wanted to 3D print the base for the generator but here I ran into real problems I have not been able to fix yet.
Big flat surfaces are very difficult on the best printers, so on my cheap printer it is close to impossible. Therefore the base is, at the time of writing, made from some MDF I had laying around.
I might go for the 3D printed version later, when I get my head around my printers "mental issues".
The bottom of the base. Mainly hollow to save PLA and raft material.
The printer currently gets "stuck" half way through the first non raft layer.
Currently not used in my build.
And we are rolling
The design of the rollers was not that big a challenge, I knew from my mechanical experience as a child (I grew up taking everything apart and putting it all back together. Not always successfully, so I think I drove my brothers mad now and then as it was their stuff I took apart.) that the rollers should be thicker in the middle else the rubber belt would not stay in place. For simplicity my first design was just two cones put back to back. That actually worked great. I did decide to base the rollers on a "stretched" sphere instead though for a few reasons:
Firstly, I printed the first set of rollers before I had noticed and fixed my printers misalignment issue, so there was some rattle when testing the generator. That's easy to hear in the video clip at the end of this post.
Secondly, I found the rollers based on a sphere more ecstatically pleasing.
Thirdly, During all the designing and test printing, I had skipped the original slicer software that came with the printer and switched to Cura, that delivers a much better result. Using Cura I don't need to auto correct all my G-Codes. I have now re-written my C# programme to only fix the misalignment issue. As I was fixing the programme anyway I changed it to a process that automatically fixes any *.gcode files generated from Cura. That way I don't need to open the file, convert it and then save it. Saves quite a few mouse exercises. The biggest and probably most important difference between the original software and Cura - it was close to impossible to detach my models from the raft. It left a very rough and un-attractive finish. With Cura my model pops off as if it was a Post-It stamp.
Left roller based on a mirrored cone. Right based on a stretched sphere.
The rollers are mounted to the frame in small ball bearings. One of the things I really like about 3D printing is the precision. The ball bearings I'm using have an outer diameter of 15 mm, thickness of 5 mm and the hole diameter is 5 mm. I did a test print with a 15 mm hole and the ball bearing slides in with a firm press fit. Such a great feeling when stuff fits like that.
The shafts for the rollers and ball bearings was a little challenge in it self. The printed parts are not very strong, specially small parts. To strengthen the shafts, I left them with a 2.5 mm hole for a small screw.
Don't forget the rubber
The rubber belt is quite an important part of the Van de Graaff generator. It is the rubber belt that carries the charge from the bottom roller comb to the top roller comb and sphere. The rubber belt actually doesn't have to be made from rubber. As long as it is non conductive and flexible, it will do its work. Different materials does give very different results though, so a bit of experimenting was needed. I ended up using a stripe of waxed table cloth. This had some advantages; It is non-conductive, it is very flexible and durable, it is easy to cut and I could just sow it together (on my very old black sowing machine) after properly finding the proper length. Furthermore, because the back side is fabric I get a very good grip on the rollers and a very smooth top surface for the charge and discharge comb.
Driving the 3D printed Van de Graff generator.
The generator we had in school was hand driven using a handle and some gears. That it was hand driven made it quite exiting as you had to stand close the generator when using it. The Van de Graaff generator we had was, if I remember right, about 40 - 50 cm tall (16 - 20 inch) and the sphere around 20 cm (~8 inch) these measurements must be taken with a pinch of salt as I was quite a bit smaller when I went to school.
What I do remember was that it took quite some strength to spin the handle on generator. It was, as mentioned, a geared drive, and the more charge the sphere became the harder it was to turn the handle.
My generator is quite a bit smaller than the "professional" ditto we had at school.
30 cm tall (12 inch) and the sphere is 13 cm (~5 inch) in diameter. I'm to lazy now a days to turn a handle - so I wanted my generator motor driven.
I have been experimenting with 3D printed gears. The results have been quite impressive - as long as you don't need high precision, high speed or high torque. In the Van de Graaff generator you need all tree, therefore I decided to go for the belt driven approach. That also made it much easier to adjust the gearing, more or less on the fly (I can just print a new wheel in ~20 minutes) thereby also adjust the speed and torque.
I had a rather large 12 Volt DC motor "in stock", can't remember from where - I think an old HP Ink-Jet printer. It seemed to be strong enough according to my initial experiments also it has a quite thick shaft (3 mm) with some good grip markers. By that, the motor became the part the rest of the Van de Graaff generator would be designed around - more or less.
Model of the motor
The Top Metal Sphere
Finally the biggest challenge - with regards to 3D printing. I still had quite a few unforeseen challenges to overcome - more about that later.
Ideally the top metal sphere should be a perfect smooth hollow sphere. That is so easy to imagine in your mind, so easy to draw in nearly any drawing programme, based on a very simple formulae.
In the real world though - my small flat in the middle of Amsterdam - creating a perfect metallic sphere is a totally different story.
First problem: Every one who has ever been building a Van de Graff generator, have been faced with this problem. From the first very old antique versions to the most modern ones. They all need a hole in the perfect their sphere. Else you will never get the charge in there. And that's the hole point of the Van de Graaff generator.
Next problem: Any sharp points will attract the charge and cause the charge to "spray" away. Smoothness is a must for a good result.
The best compromise for a perfect sphere with a hole, is merging the sphere with an other, in my opinion, perfect object - a doughnut.
A "X-Ray" view of the top sphere
This design is the one I remember from my school days, and the design you see in more or less any (semi) professional Van de Graaff generator. In short this design makes sure any "spraying" of charge stays inside the sphere, no sharp points on the outside - in an ideal world. The smoother and larger the sphere - the larger charge it can hold - the longer and stronger sparks.
It is all coming together.
By now I at least had an idea how to get it all together. I'm still only talking about 3D printed parts. All plastic. Not a lot of very High-Voltage in that.
Fortunately only very few parts need to be conductive, actually the less metal the better. Only the top roller and top sphere needs to be conductive. Apart from that only the corona combs and connecting wires need to be conductive.
How the get those two plastic parts conductive? Searching the internet gives some options. Electroplating was on the top of my list for a while. There are some quite convincing examples on the web. But generally always small objects, and a lot of mess with (homemade) chemicals.
As a child I loved playing with chemicals. Made lot of interesting (and sometimes quite smelly) stuff you wouldn't be allowed to do, legally, today. Now a days I find chemistry interesting on a theoretical level - practically it's not for me.
I went in a different direction. I often build my DIY electronic stuff in to wooden (MDF of multiplex) cases. To create an electric shield I have often used graphite spray. The spray creates a matt conductive surface, with a resistance of couple of kOhms per cm/inch. Good enough for shielding electronic stuff. Also good enough for a Van de Graaff generator? In your dreams.
Next idea. I had a big role of self adhesive aluminium tape. What if I covered the inside and outside of the sphere with segments of that. It would create a nearly perfect surface, of cause creating a sphere from flat segments is impossible - but if the segments are small enough we are getting close enough. I have seen working Van de Graff made from Cola cans. So a few bumps could be allowed.
Well though the aluminium tape is conductive, the self adhesive glue isn't. Back to the drawing board...
Late night, turning in bed, a bright moment. Combine aluminium tape with graphite spray. Wouldn't get a shiny metallic sphere, but it might work.
Next day I read through the data sheet of the graphite spray i was using. One thing that stood out was, if the object coated with graphite spray is polished, with a soft cloth, you not only get a shiny surface, as a free gift, the resistance goes down by quite a bit.
Before applying the aluminium taps I polished the 3D printed sphere to the smoothest surface I could manage. I first used a 120 grain sandpaper, followed by a 800 grain polishing, finishing off with 1200 grain paper.
Making sure the sphere was dust and fat free, I started to apply the segments of aluminium tape. Inside first. The surface of the inside is not that critical, so it was a good for testing. After finishing the inner surface I tried measuring the resistance between two segments and, as expected, no conduction. After that I applied a coating of the graphite spray. Let it dry night over, then gave it a gentle polish with some kitchen paper. Now the resistance between any two points was always below 200 Ohms.
I repeated everything for the outside. Here I was a little more careful with the placing of the segments. After the graphite coating the resistance between inside and outside of the sphere stays at around 200 Ohms.
I finally had overcame the biggest challenge - the top metal sphere. Success? Nahh - there was still a few obstacles before I could drag the first sparks.
Left Aluminium tape only, Right coated in graphite spray and polished.
At least I now had all the major parts of the generator on the drawing board (and quite a few bits and bobs in the recycling bin)
Before finishing up the 3D printed parts, as mentioned earlier in this post, the upper roller also need a metallic surface, not a must, but a big performance booster. Here I just covered the roller in the self adhesive copper tape I also used for the corona combs.
The next few parts I needed was the charge transfer combs. The bottom comb is needed for transferring the charge from the high voltage source to the belt by corona discharge. The top comb transfers the charge from the belt to the top sphere, again by corona discharge.
For both combs I used self adhesive copper tape. I could have used the cheaper aluminium version, but I had copper tape in stock and big advantage - you can solder wires to it.
To create the comb teeth, I just cut, surprise, teeth in the copper tape. A little fiddly, fortunately the comb does not need perfect contact with the rubber belt as the charge is transferred by corona discharge.
Close up of the charger comb. Here temporary covered as it is referenced to the 240 line voltage.
The Van de Graaff generator before I coated the top sphere with graphite spray.
The finished build - nearly.
The box under the Van de Graaff generator is a negative Ion generator based on a 11 stage voltage multiplier. It delivers around -5kV to the lower corona comb.
The Ion generator is referenced to the 240V~ net and though the output have a couple of 10 MOhm resistors in series it should not be toughed. It still really hurts.
A closer look at the top sphere and the connection for the top corona comb.
The sphere is covered inside and outside with self adhesive aluminium tape. Above that a coating of graphite spray.
The wire is fastened by fanning out a multi core wire and gluing it to the inside of the sphere, fixing it in place with a squirt of hot-glue.
Model as rendered in OpenScad.
Model as rendered in OpenScad - Exploded view.
Close-up of the base assembly. The 12V= motor is powered by two small switch mode power supplies I had laying around. The charge is transferred to the lower corona comb by the yellow wire,
And we do need a few sparks.
Hello from sparky. A single spark from the video below.
A short Y-Tube video drawing a few sparks.
This is before I fixed the misaligned rollers so the Van de Graaff generator is quite noisy here.
OpenScad: I heard about OpenScad on BigClives Y-Tube channel. I wanted to give it a try. I fell in love immediately. Everything you build is based on a few simple basic shapes; spheres, cubes, cylinders. You write your model in a language that reminds me a little bit about a "real" programming language. You can use for loops, if statements, there are loads of mathematical and geometrical functions.
All the OpenScad source files for the Van de Graaff generator can be found on my Thingiverse page.
Here you can see all the 3D printed parts.
The (currently not used) base plate.
The roller shafts. The hole makes a snug fit for a 2.5 mm screw. This is for strengthens of the shaft.
The bottom corona comb. The yellow parts are self adhesive copper tape.
The top corona comb. The yellow parts are self adhesive copper tape.
The bottom part of the frame. Print twice.
The middle part of the frame. Print twice.
The top part of the frame. Print twice.
Bracket for the motor.
The motor drive pulleys.
The roller. Print twice.
The spacers for the frame. Print 3 times.
Holder for the top sphere.
Top sphere.
Cura: I switched from the original slicer software, based on The Replicator, that came with my 3D printer to Cura.
C#: Used for my misalignment correction programme. It also contains a simple preview function of the generated G-Code.
Power supply:
Low voltage - Two small 12VDC/500mA switch mode supplies in parallel. It was what I had in stock.
High Voltage - An 11 stage voltage multiplier, normally used as a negative Ion generator. The output is around 5kV.
