Egg robot Number 1

The first egg robot was hatched when Bruce Shapiro in 1990 dreamed up the Eggbot™. Bruce published it as an open-source design for both software and hardware however the name is trademarked. While it is available for purchase as a whole machine, I wanted to see if I could 3D print one myself since the initial cost was large.

I found another design by Probot that seemed to do a reasonable job, and although many of the other ones such as the SphereBot are larger this one seemed to produce reasonable quality and I had most of the parts:

  • 308zz bearings
  • 3D printer to print parts
  • Arduino
  • silicon egg cups moulds
  • stepper motors
  • stepper motor controllers

… and that was about it. Most of those I had, the rest I could order easily (for example, I had Nema-17 steppers and this only required 28byj-48 ones, either 5V or 12V). So, in a fit of decision I launched into building it and surprised myself with how quickly it came together.

The base and cover are easy to print with the sides of the cover bending into a living hinge. The ends are bolted shut and there is a sliding swing arm and end stanchion. The living hinge is an interesting design choice which leads me to believe that the designers were very familiar with 3D printing as it avoids overhangs in the upright sections of the print. It does make a very neat and attractive package when finished.

The challenge comes because of the interaction between different things which were not designed together: hardware and software. The original hardware has an actual PCB created to control the movement, whereas the design I am using replaces that with an Arduino running software called EggDuino. That software has to emulated the responses and obey the commands expected from the original PCB so that it can print things. All this is controlled by an extension to the open-source software called InkScape that sends commands to the egg-robot! Lots of moving parts in this design and 3 different things created by different people does give lots of room for error. So the process goes like this:

Inkscape → Eggbot extension → Arduino running EggDuino → egg

The ‘tail stock’ – if this were a lathe – is based on a printed part with a 308zz bearing inside. The 308zz are a very common type of bearing, sometimes called ‘skateboard bearings’ as they are ubiquitously used for skateboard wheels.

Once completed the whole machine is connected to a computer by USB cord and you use Inkscape to create and print the eggs.

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Blutack and masking tape

I’ve started masking the base PCB of my WiFi doorbell and I am using both masking tape and Blutack. I discovered the Blutack while going through my stationery drawer looking for something similar to the latex masking fluid which is used in real electronic waterproofing. I had thought of using an eraser which would be soft and pressed onto the micro-USB port would mostly seal against the conformal spray. The Blutack is now my best friend for masking, even if the spray dissolves it some and leaves it sticky – but the easiest way to remove Blutack is using more Blutack, which worked very well on the PCB board.

I decided to leave the camera alone as it was already in a unit, and previous experience has taught me that getting near lenses with any type of fluid or compound invariably means that you leave smears, no matter how careful. As it is a single unit I’ll seal around its seating and hope that that helps prevent major water ingress into the rest of the mechanism. If the video feed fails, I’ll know better next time!

The speaker at the bottom is also hard to waterproof: cover it in conformal fluid or seal it in somehow would mean that it likely could not be heard, and similarly for the microphone which needs to vibrate to detect speaking. I’ll simply seal around the edges of those components and hope that their internals are okay with a little moisture.

Miniature speaker at bottom of unit

The door-press button is difficult, as it needs to move to trigger the micro-switch, but isn’t sealed around its edge – I assume that rain against the front of the unit seeps through capillary action around the edges and into the major internal space, and thence via condensation onto other surfaces. That’s bad, as it possibly means I cannot seal one of the areas of major ingress.

Press button is … difficult

Experimenting is fun, so I am going to try a thin film of plastic wrap (sometimes called ‘cling film’ here – other names elsewhere!) glued to the rear of the face plate to see if that works. The plastic film should bend enough to allow depressing the micro-switch, but the real challenge will be getting it sealed against the back of the face plate. I will try a rim of silicone sealant to which I will press a square of plastic film.

Overall the task took me the whole day. While that seems a little crazy (and you may prefer watching box sets on television), I saw it as a learning exercise and bit of a challenge! I’ve thought through how to waterproof a very difficult piece of equipment and although the proof that it’s successful still remains, I am overall pleased with the result and would attempt something similar with greater skill.

The doorbell does work now and I have tested it both via pressing the push button and the mobile app. Bring on the rain!

Waterproofing electronics

I’ve been interested in getting a WiFi doorbell for my house. Having looked at the issues surrounding the two market-leading brands, decided to go the cheaper route and purchased a no-name brand from China.

The doorbell and separate chime are excellent, but are not waterproof.

I experienced this after having had the doorbell working for a week or so – England is anything but dry and before Christmas a downpour lashed our front elevation for around 18 hours, thoroughly wetting the outside of the unit. While the camera still worked and I could connect to it from my phone app, I did not suspect that water had entered the compartment. When it did occur to me was after one door press by the post delivery worker that left a lingering ‘ding dong’ in the air after it should have stopped.

The next day the lingering ‘ding dong’ did not stop at all and I had to remove power from the chime unit. I opened the unit and saw moisture inside and dried it out, but realised several days later that I could not connect to the unit from the mobile app and so have taken it off the wall to fully waterproof it. Thankfully the ringing had stopped but I worried that it could re-occur in the middle of the night or while we were away.

Components of the video doorbell

I will use electronic conformal liquid in a spray form to coat the PCB and internals, and will try to either glue non-moving parts in place with silicone sealant as well as putting a bead around the external rim of the back-plate. My challenge is that there is several holes where ingress is needed for the microphone and the speaker! How to waterproof those? And the press button will still have to move inwards to depress the micro-switch and if glued solid it could not do this.

The reason the High Street died

In the UK the major shopping district is colloquially called ‘the high street’. Other countries may call it the CBD (central business district – but more generally this is the office and skyscraper part of a city), downtown, or simply ‘the shops’. My local town here in the UK has one named The High Street and this isn’t unusual for England as it is the most common street name. With the advent of online shopping in the early 2000’s and the rise of Amazon there was much consternation at the plight of bricks-and-mortar shops on the high street. TV programmes that aimed to remedy the flight away (notably ones featuring Mary Portas – ‘queen of shops!’) were common, there were government grants and industry worked with academia to study the issues – I know, because in my professional life I took part in one such study.

But the shoppers continued to flock to the online retailers and everyone was puzzled. Discounts, robo-shoppers (research online, shop in store without browsing), price matching and all manner of techniques were put forward. Card networks offered to analyse patterns and events were held in target towns. Yet, from my personal and anecdotal experience I’d have to point at one major reason why people are turning away from shopping in person especially at the larger out-of-town warehouses.

Rudeness.

I’ve just come back from picking up some items from one of the large chain store brands here in the UK and my experience was infuriating. I struggled to the checkout with a large TV and no-one offered to help, whilst the store was mainly empty with assistants wandering the aisles. We had a gaming console plus assorted other items and our purchases were a sizeable part of £1000 – so not insignificant. At the checkout the assistant immediately started up-selling product insurance and when I declined insisted on asking why? He also wanted to know my street address and email, and when I also refused those insisted that the purchase would not go through without them. Actually, the store already had them as I have an account in their online shopping system and had reserved the console earlier. But what shook me was the general abusive approach taken to the sale; countering my every decline, challenging my refusal to take insurance, insisting on more personal detail and so on. As we struggled to lift the items from the counter he stepped back and turned away – not even offering to hold them while I took some to the car. Perhaps it was just me, or a latent racism on their behalf – but this retailer as a whole has a ‘bad’ rating on Trustpilot with five-figure negative ratings. I felt unwanted and used.

Recently another large out-of-town shopping warehouse has gone bankrupt and when I read forums on Toys-R-Us and their decline many people mentioned the shambolic store layouts and disinterested assistants. If shopping is all about experience, as many retail consultants believe, then it is important that shoppers feel great about what happens to them, not abused. I’ve spent long enough in the cut and thrust world of business and even time in retail as a IT consultant, so I understand the pressures and analytics which drive certain behaviours. Scanning time for checkout operators, forced meet-and-greet, up-sell and cross-sell all sound good on PowerPoint but in reality shoppers are looking to feel good and have an enjoyable experience, not just acquire goods out of necessity.

I’d have to identify rudeness as a major reason why the in-store experience puts off many shoppers in England in the larger chain stores. Contrast this to a recent bookstore – surely an endangered breed if ever there was! – and the utterly other experience of an assistant looking people in the eye, asking how they were and did they enjoy that type of genre, wishing them well with their purchases and offering to go the extra mile and lookup stock if needed. You felt warm and appreciated and even though I seldom purchase physical books now, I have repeatedly gone to that store simply to browse. I felt good, I felt human, I felt wanted.

Adventures in waterproofing 3D prints

I’ve started printing 3D vases which look really nice in metal filaments.

3D prints are prepared by making the shape in software and then ‘slicing’ it into layers which can be understood by the printer. Usually this means that several layers are placed on the bottom, the side walls are built up by multiple passes of the print head, the top is a repeat of the bottom and the middle bits which are not seen are filled by ‘infill’ in special patterns. All this makes for strong objects.

There is a special mode of slicing which ensures that the print head never lifts off the work being printed, and never ‘retracts’ the filament nor moves backwards. This is sometimes called ‘vase’ mode and makes the print into a long spiral all the way to the top. There are few objects for which this works properly since it makes the sides only one layer thick and there is no infill. On vases or drinking glasses, cups this is ideal however and with the proper sized nozzle and good filament the results are great.

One issue is that usually these are not waterproof. Filament and deposition manufacturing by their nature leave microscopic holes in the print and while tuning the slicing parameters and the printer can have some effect, generally it is just luck when things hold water.  I’ve decided to look into lining the inside of objects to see if their water-tightness can be improved and so far I’ve read or seen of a few ideas:

  1. A wax or waxy substance rubbed into the surface then allowed to dry,
  2. liquid latex, of the type used for face painting,
  3. PVA wood glues of different types,
  4. general purpose epoxy resin, sometimes used in the fibreglass manufacturing industries. One I have found is called ‘Epolam,
  5. acrylic conformal coating used in the electronic industry for coating PCBs,
  6. … or general spray paint coatings.

Of these, the conformal coating sounds good but is very expensive. I’m going to try some of the other ones first to see if they are effective and attractive, starting with the cheapest which seems to be the wood glue and liquid latex. I wouldn’t want to mar the appearance of a beautiful vase by having a thick visible coating, but I also don’t want that vase to leak.

Redemption

The roots of the word ‘mortgage’ mean something which is paid until complete. Some macabre definitions float around the internet including those which take the old French or Latin and read them in English, which is always a dodgy way to interpret languages. I saw ‘death-pledge’ being touted as one due to ‘mort’=death and ‘gage’=pledge, which sounds too simplistic.

Different countries also have other expectations about how to finance buying a house – I was surprised to learn in Turkey that colleagues of mine there would take a loan from the property developer, and repay in a matter of years rather than decades. I’ve always lived in countries where the loans are taken through financial organisations and paid over decades with low interest rates that compound because of the extreme length of time involved.

The process of removing this debt is called ‘redemption’ and is removal of the pledge-until-payment and release of the deeds which show title in ownership. While that is nice, it feels a little medieval and reminds me of the long history of land title and ownership. Real land reform is quite rare and has mixed outcomes, not always helping either the rural poor nor the lower classes. I do admire the land reforms in Scotland which include returning tracts of land to common or community ownership.

It is nice as I redeem my own house to learn of the different ways that governments and rulers – some quite surprising – have redistributed land and tried to encourage greater wealth and ownership.

Parametric modelling

I’ve been using a number of programs to design 3D parts. While there are a number of very good commercial offerings these are very costly and my budget does not stretch that far. Autodesk is a particular favourite as they seem to provide quite a number of tools in this space including photogrammetry, mesh modelling and parametric CAD. Their TinkerCAD is pretty good. I’d love to use their stable of tools but as a maker and hobbyist they remain largely out of reach.

Instead I’ve been trying the free and opensource tools and they very in ability and usefulness. While Blender is perfect in the mesh modelling space and my son is pretty good with it, like a lot of comprehensive tools you need to devote the time to make it become familiar. For a while I’ve use FreeCAD and some of it is pretty amazing, but as there is many ‘ways’ to accomplish the same thing it can get confusing at times. I’ve made a few models using it.

Support

Recently I’ve started using OpenSCAD and are really enjoying it. OpenSCAD is a little unusual as it is a programming language of sorts and you do not operate in a WYSIWYG mode – instead creating the model in your mind and then translating this into distances and objects. A great tutorial on OpenSCAD is over here. Its power comes from using geometry in a Cartesian reference space to combine, intersect, and subtract objects to create your model. I find it very powerful and easy to use as I can easily visualise 3D objects.

I’m building an enclosure for my 3D printer and will keep a record here, while making the objects available on Thingiverse for others to use.

3D prints everywhere…

dav

I’ve started printing lots of things with my 3D printer, maybe too many things! There were the normal table top figurines, busts of film characters, and printer test prints but then the bug really caught hold and I am in the midst of building a veritable mini-factory of sorts. Here’s my project list:

Projects

During the build of the 3D scanner, and while waiting for the parts to arrive from China, the US, and Europe I started another and began to get confused which project was which. Time to focus, methinks. The scanner is almost finished in its first incarnation and I’ll be able to use it for my future activities.

The end point of all this is to set up a mini-process line where I can produce small trinkets and sell them in my church’s Christmas fair in late November. We’re fund raising for a new building which involves mortgages, loans and long term commitment to a large community building, hence the fund raising.

How do you rotate a PDF?

Searching the internet for information on how to manually rotate a PDF finds lots of frustration. The reason I have done is this that my scanner produces pages rotated 90 degrees, and the times I have searched the internet over previous decade the answers have depressed me:

  1. Buy Adobe Acrobat Pro,
  2. Send your document off to an online service – dodgy if you value the information on that PDF,
  3. Download a program to do it, again suspect as you cannot examine the source code or understand the provenance of some programs,
  4. Buy a Mac, as the Preview preview on a Mac can do permanent rotation, and save the rotated document.

A lot of those ideas are bad for different reasons. Acrobat Pro is expensive for simply rotating a PDF; online services, even those that promise not to peek at your document, do have control of it; running strange programs isn’t recommended at all; and the world of Macs are wonderful and expensive.

There is a simpler way.

Some of the raw material in a PDF is in a format which describes the document in plain text, while some is in a binary format. The binary bits are best left alone, but the plain text parts are easy to edit in a good editor. I used Notepad++ but there are others such as Sublime Text or Atom. I realise that this is “download a program from the internet…” dressed up in different words, but these well-known editors main job is to faithfully edit things and save them without collateral damage. I also use them frequently for playing with programs that I write, so I trust them.

Within the first few lines of a PDF you will likely find a line like this:

/Rotate 0

Save a copy of the document first, then edit this line to some other multiple of 90 such as ‘180’ or ‘270’ then save the document. Multiple pages will have their own rotate declarative, so find those as well and change. On viewing the document now the page(s) will be rotated clockwise that amount of degrees. Job done!