Planet Nottinghack

10 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Potato Prints and Custom Wrapping


Craft time for the whole family, we're all at home so decided to make some wrapping papers. We started with simple brown paper and carved some potatoes to make printing stamps. For a second sheet we drew a single black line across a page and then finger painted a string of lights onto it, these should provide enough wrapping for a good handful of presents.



by noreply@blogger.com (Martin Raynsford) at 10 December 2017 04:29 PM

09 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Jurassic World Jeep (and gate update)


If we were making a Jurassic world cake and we already make cake cars we'd be a bit foolish not to make a Jurassic world Jeep. The jeep had a custom version of the car base to lift the vehicle a bit higher up but the mechanics are all essentially the same, meaning the car base can actually be quite versatile. Dawn covered the platform with cake and icing and did all the difficult decorating parts that actually make it look like a car, it's a very impressive job that I believe was completed at stupid o'clock the morning before the event.

There's even video of the car driving through the gates (the car determined the size of the gates). I'd like to point out that I wasn't there though because friend don't let friends take vertical video.







by noreply@blogger.com (Martin Raynsford) at 09 December 2017 05:21 PM

Car Production done


It's been a busy week getting these cars into production and after a late night last night I finally finished a batch of 8 cars ready for workshops this weekend. I delivered them to Nottingham first thing this morning and as far as I know it's all going well which means I get to sit back and work on some other projects this weekend (Like catching up on some blogging). In the meantime here are some pics of the completed cars.



by noreply@blogger.com (Martin Raynsford) at 09 December 2017 04:19 PM

08 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Car Shells 2


The remote car cakes have a layer of plastic between the cake and the electronics. This needs to be shaped to fit the wheels and provide enough space for actual cake to go onto the car. The vacuum former is the perfect tool for this. I started by taking a mould of an actual toy car about the right size, this ended up being a one shot deal as the toy car melted on the second pull. 


At this point I had a sheet of plastic in roughly the right shape and a strong desire not to mess up a second time so I scrabbled around the garage to see what my options were. I found a bag of plaster of paris and decide that casting the mould was a sensible way forward.


The plaster of paris was cast, the kitchen was turned upside down, nearly every available surface turned into useful space full of junk, at least I had a few hours to tidy things up again. It was all a bit impromptu but good fun. The plaster of paris former was cut into separate parts for the cake. The middle section will become a mould for the cake part of the car, the nose and bonnet will house the electronics.


The plaster of paris parts were shaped, padded and mounted upon a base to hold them in the right places. The wheel arches were built up to allow ample room for the wheels. This new mould served well for the first half dozen cars, it was a bit of a struggle to remove the mould after it was formed and it started to show signs of wear which led to a mould rethink but that's for another day.



by noreply@blogger.com (Martin Raynsford) at 08 December 2017 01:14 PM

07 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Wheely fun times



The remote control car cake design was refined to a point where we could run workshops on it, allowing other people to make them. This means small production runs of parts, last night I sat and assembled 32 wheels, each one made from 5 layers of material and then I squeezed rubber tyres onto them. It's mindless work but it needs to be done and at least I get to watch TV at the same time.


by noreply@blogger.com (Martin Raynsford) at 07 December 2017 11:56 AM

04 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Airbrush paint for infill


I cut some more wound point counters tonight, but this time I used air brush paints to fill the lettering. It's thinner than normal acrylic paint, offers great coverage and dries quicker. I definitely recommend it for infill effects.


by noreply@blogger.com (Martin Raynsford) at 04 December 2017 11:26 PM

03 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

BB9E cake


I had the pleasure of attending a Dinkydoodle Designs cake making course today, it was great to go along and learn how to make the cake that goes around the droid heads I've been making for the last 2 years. Because BB9 has a flat top I had to rebuild the whole mechanism to make it fit into the available space, I took the opportunity to make some needed improvements, such as vacuum formed heads and bearings for the moving parts. I also decided to add an ESP8266 into the mix so that the whole thing could be controlled from my phone. I had a great day and would really recommend it for anyone who is looking for something different to do.




by noreply@blogger.com (Martin Raynsford) at 03 December 2017 07:58 PM

02 December 2017

Martin Raynsford hackergotchi for Martin Raynsford

Present for Santa


Eli drew a picture of a small present he wanted to make for Santa. He measured the size of the bag to find the right scale and he drew the design out on inkscape with a little bit of help. I set up the laser to cut on a small piece of illomba faced poplar ply that he picked from the scrap pile and 45 seconds later we had the item made. 

by noreply@blogger.com (Martin Raynsford) at 02 December 2017 04:05 PM

30 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Jurassic World Gates


The control box I made the other day was destined to be connected to this set of Jurassic World Gates. The gates are modelled after those in the film, the LED lights flicker like real torches, the gates open and close (and stop at the limits of their travel) and the whole thing can play the Jurassic World theme tune. This framework will head off Dinkydoodle Designs to be covered in cake and icing.





by noreply@blogger.com (Martin Raynsford) at 30 November 2017 11:06 PM

27 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Quick control box


I've been working on a cake this weekend, bit of a rush and I'll be able to reveal the whole thing before the end of the week. For now I put together a quick electronics box to give it a polished feeling. The most recent version of inkscape comes with a lot more choice of Hershey text so I opted for a rather nice font on the switches to denote the functions.

by noreply@blogger.com (Martin Raynsford) at 27 November 2017 08:44 PM

24 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Santa Keys


The school asked me to cut a selection of santa keys for their Christmas fair. It was a simple drawing and cutting keys from my mdf scraps. (svg here)

by noreply@blogger.com (Martin Raynsford) at 24 November 2017 04:26 PM

23 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Car Body Shells


The basic car framework needs a food safe covering to go between the cake and the electronics. Thankfully when I bought my vacuum former this project was already on the cards so it's a perfect excuse to use it. I laser cut a basic mould from ply and assembled it as a mould to form over. The cake needed to clear the wheels and provide turning clearance for the steering. These covers came out pretty well, the trouble is that vacuum forming works best with a 3 degree angle on the edges and the laser cutter cuts perfectly vertical so it was a bit of a struggle to get the mould out. This was when I introduced an air pump to the vacuum former. Applying a bit of positive pressure after forming releases the mould a little and made it easier to remove.


by noreply@blogger.com (Martin Raynsford) at 23 November 2017 09:19 AM

22 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Remote controlled car cake


As well as making my own cake for cake international, I've been rather heavily involved in making these remote control car cakes. Once you add sugar paste icing and a large chunk of cake these things start to weigh quite a lot so moving them round becomes quite a tricky challenge. This car has been through a few iterations before it will go into product development, this is the first version.


I decided to use the ESP8266 wifi chip to function as a controller on these devices. They're able to act as a webserver and deliver HTML pages directly to your own device without the need for any kind of app. As most of the people in the cake world seem to use iPhones and I have android seemed the easiest solution.


I wanted the car to keep the traditional Ackermann steering mechanism, so I used a servo to directly drive a linkage mechanism. The little 9g servo just about coped with the turning forces but it needed to be enlarged once all the cake was put on top of it


Two motors controlled the rear wheels, these were directly attached to the drive wheels. Wheels and motors were bought as a single and designed to be connected together. The motors were driven by an L298N dual H-bridge chip.


This iteration was functional as you can see in the video but it all needed beefing up a bit to provide any kind of longevity. I'll discuss more of the design in the next post and try to keep you all a bit more involved while I'm stuck in development mode.

by noreply@blogger.com (Martin Raynsford) at 22 November 2017 09:28 PM

18 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Frivolous #Makevember


I bought some cheap LED clock kits a few years ago, they were good fun to assemble and left me with a perfectly serviceable clock for the kids rooms. I opted not to buy the (nasty plastic) case because it was laser cut and I could make my own, move forward a few years and today seemed like a good time to actually do that.

It's a simple wooden box really with holes in the correct places, the clock module slides in loosely from the front and wedges in place with some foam. The plastic panel slides into some grooves along the front of the box. It's transparent grey plastic so the LED's can shine through it. The grooves on the front mean that the burnt side is out on the top of the clock, I should have masked it to reduce those marks. Being wooden I can easily glue it to the underside of my shelves next to my hooky hooks (svg here)



by noreply@blogger.com (Martin Raynsford) at 18 November 2017 04:44 PM

16 November 2017

Spencer Owen hackergotchi for Spencer Owen

Rock Light

This is one of those little projects that didn’t need to be done, or could have been done very simply.  Despite a lot of feature creep, everything just came together at the right time, and I’m really pleased with the results.

Firstly, a bit of background.  My mum celebrated her birthday a couple of months ago, and the present my sister bought her was a geode that she picked up on a recent holiday to the United States.  Not just a regular geode, though, but one that had a hole drilled out and a light attachment that went inside so it glowed nicely.  Well, it would have glowed nicely, except that the US bulb was rated for 110v, not our full strength 220v electricity.  So the millisecond it glowed nicely for was followed by a loud bang and the bulb turning black.

As I was there to see this, I figured I could easily get a light fitting and bulb from Ikea and we’re all good.  Then I wondered if LED lights might be a better idea.  At the same time, I was starting a project for the RC2014 involving a ESP8266 wifi enabled micro controller.  Coincidentally, I’d just bought a couple of WS2812 based Zip Sticks.  So, you can guess where I’m going with this, right?  Yup, use the ESP8266 to set all the LEDs to a nice shade of blue, and job done!

Well, that would have been within my programming abilities.  However, I wondered if anybody else had controlled WS2812 LEDs from an ESP8266.  Would you believe they had?  And not only that, but I found McLighting from Toblum on GitHub which enables wifi control from your phone or computer to not only set the colour, but a whole stack of pretty effects.

Time to fire up KiCad and get a PCB designed.  I’d taken the rough measurement of the hole in the geode, and had a 40mm diameter round PCB to fit everything on.  With a mixture of through-hole and surface mount components, and using both sides of the board, everything went on well.  Because I only needed a very small run, OSHPark was the obvious choice.  And at only $11.25, it was a real bargain!

A few days later and 3 lovely purple PCBs arrived.  It wasn’t long before I got the soldering iron out and started to assemble them.  I assumed that my selection of every single value of surface mount capacitor would have contained what I needed, but sadly it didn’t even get close, so I had to resort to bodging in a couple of through-hole electrolytic caps.  I also noticed that I hadn’t indicated the +ve or -ve power terminals.  A rookie mistake, but not the end of the world.  Once it was all together, though, it worked just great!

  

A quick test, and a run through of the settings and things were looking really good.  But would it fit the geode?  Time for a trip down to my parents house and try it out.

The PCB went in to the geode with no problem at all.  If anything it was slightly undersized, but I’d prefer it to be a little bit too small than too big.  A plastic ring that was a snug fit held it securely in place.

In the daylight, it looks absolutely awesome!

  

By night it looks even better… although getting a good photograph isn’t so easy!

by Spencer at 16 November 2017 12:29 PM

12 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

100 Blood and Oil Trackers


As is their right, the blood and oil guys decided to go with acrylic for their counters. The acrylic is a bit trickier to glue together and all of the lettering has to be done with infill techniques. I decided to opt out of the assembly process for these and instead supply bags full of parts :)


by noreply@blogger.com (Martin Raynsford) at 12 November 2017 10:19 AM

11 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Blood and Oil Tracker


I made this simple, magnet free version of a score tracker for Blood and Oil. I used 0.8mm birch for the front and back panels and 3mm poplar for the middle layer. The lettering was done with Hershey text to make it as fast as possible and the emblem is a combination of engraving and outlining. The idea was to make these as quick as possible for a batch order but I also liked the super skinny style. 



by noreply@blogger.com (Martin Raynsford) at 11 November 2017 10:12 AM

07 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

The Days Cutting #Makevember


A family of large meeples from 12mm plywood, coloured before cutting. I really should mask the reverse or clean my honeycomb to make them look better after cutting.


A customised start tile for Carcassonne. Somebody wants to use a set as a guest book for their weddings, having the guests write messages on the rest of the tiles.



A quick stencil for painting some fabric. It's for a cosplay costume, possibly one of the super hero suits?

Finally here is the days orders, a mixture of marble machines, kits and other custom parts (like the meeples)

by noreply@blogger.com (Martin Raynsford) at 07 November 2017 06:36 PM

03 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Edible Marble Machine


Around three months ago I found out I was going to be exhibiting at Cake International this weekend, I've been before and as well as the usual demo stalls and retailers there is a vast array of stunning cakes presented as competition entries. I thought I might as well throw my hat in the ring and join in with an entry. I've been working on it almost solidly for the last two weeks, so here it is, an edible version of my marble machine.

 


'Cake' is rather a loose definition based on most peoples understandings, these are mostly decorative exhibits and the competition itself is heavily categorised, each with different rules about what is and isn't acceptable. Some exhibits must contain cake, some can use dummies instead, some can use internal support structures and some must conform to a theme, you can see the whole categories here. I aimed for category M, 'Pushing the Boundaries' where pretty much anything goes any medium, internal supports and wiring could be used. I wanted to make my machine 100% edible but that gave me the widest range of fall back positions (after all I didn't know how I was going to do it when I started)

I had intended it to be a simple build, laser cut myself some gingerbread and assemble the parts. I ran some initial tests and I was able to make functional gears, I could rebake the cut gingerbread and get it to sink into a spiral shape and it all appeared to be going well. A few days later however I had noticed that the gingerbread parts had all sagged. I baked more gingerbread without any leaven ingredients I doubled and tripled the baking time but to no avail. I had to go back to the drawing board and find a new medium to work with.

IMG_6294 (Custom).JPG

I tried more tests on a wide range of materials, gum paste, sugar paste, royal icing and different biscuit recipes, I finally settled upon Massa Ticino sugar paste, mixed with a healthy dose of tylo powder to harden it. Once left to dry it hardened enough to span the distances I required. That left a problem of timescales, I couldn't wait 36 hours for each part so I had to borrow a food dehydrator to speed up the process. 8 hours at 50C seemed to work well and I could wake up to fresh parts each morning. All the parts would be cut by hand from rolled sheets, often using laser cut wooden parts for patterns. The edges of all the part were painted brown to made it look as though they were laser cut.


Each exhibit needs to be presented on a base board, like all my projects I decided to set the backdrop to be the same as my kitchen bench (I've seen comment elsewhere on the internet that somebody knew a project was my work because of the bench backdrop). There are lots of good tutorials about making wood grain patterns so I just followed one of those. The base board gave me something to build upon and to figure out where to put things, I always knew this would be a double sized machine really.

The next significant part was the spiral itself, this was always going to be too big to fit in the dehydrator so it would have to live in the airing cupboard for a few nights. The spiral had to be built in place upon it's vertical stands so the framework had to fit around all of those parts. A spiral was glued down into wooden frame and then cut into 4, each loop would now be supported and once dried the frame could be removed in sections. This ended up being incredibly useful to ensure the item didn't break during transport to the event.


While the spiral was drying I made the vertical panels that hold the main gear in place. The gears were going to be heavy and all that weight would be put through a single point of the panel so I decided to double up the wall thickness in strategic places. The spiral attached to the top hole and was glued into place using sugar glue. The secondary rail was also glued into place and supported at the other end by one of the verticals on the spiral.


The gears were made with 3 layers of sugar paste to make them 20 mm thick (wide enough for a ball bearing). The larger geared weighs nearly 1 Kg which is a lot of shear force to put through a small disk of sugar paste held on with sugar glue. The solution lay with dried spaghetti (the cake only has to be edible, not tasty). Strands of spaghetti were pressed through a stack of disks that formed the axle stubs, liberal amounts of glue was placed between the layers in the hope that it would strengthen the joint and finally the whole stub was painted with edible shine, which is kind of like varnish for cakes. The inside of the hole was also varnished with the hope that the two smooth surfaces would produce minimal friction. 


I used a fresh piece of sugar paste to make small end caps to the axles and hide the spaghetti. I also glued the handle onto the smaller gear, at this point it had to go through the second vertical panel. Both pieces were now awkward and couldn't be placed flat upon a surface so I quickly knocked together a jig to support the weight while keeping the ends safe. The teeth of the gears were also varnished to add strength and reduce friction. After some initial testing (and videoing) the whole machine was reassembled on the day at the venue.

IMG_6302 (Custom).JPG

The edible marble machine obviously can not be motorised so most of the time it's going to be static on display (I can't let random members of the public crank the handle because they'll break it). To add some motion to the exhibit I also made a small wooden marble machine with a motor. This smaller machine was an exact replica of the new cake version, reinforced in all the same places. It was placed on a wooden board next to the cake board along with some text describing the arrangement and inviting the judges only to use the machine.


Day 1 is now complete, the Judging phase is over, as soon as I have some results I will let you know how I fare.

by noreply@blogger.com (Martin Raynsford) at 03 November 2017 11:15 PM

02 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

Quick Jigs - #Makevember


My current large project (details soon I promise) has produced some large and bulky parts that can't be laid flat on a surface but need supporting fairly equally all over. A quick run to the laser and I have parts that support in all the relevant places. I left a lot of gaps around the edges so sadly they would be better if they were a tighter fit. Next time I should check and measure rather than guesstimate but they will do the job and they only took 10 minutes. Now, back to my video editing....


by noreply@blogger.com (Martin Raynsford) at 02 November 2017 01:15 PM

01 November 2017

Martin Raynsford hackergotchi for Martin Raynsford

First day of #Makevember


Every day is a learning day here where I try new things and make something new. Makevember is encouraging people to make one thing every day, I don't know if I'm going to be able to do that (especially when I'm exhibiting at the NEC for 3 days this weekend) but I would hope to start using some of my newer tools a bit more. In the meantime I thought I'd just post some of the things I've made today. This is a selection of all the things I'm allowed to show you, I've actually spent most of the day working on a large project (more details on Monday).

One of the important things about doing this every day is that you learn something from everything you do, I'll also briefly describe what I learned from these things.

Pictured above are some car shells for remote control cake cars. These were vacuum formed from 1mm HIPS and I learned a lot considering I haven't formed anything for a few weeks. Plastic sheets come in multiple sizes, buy them too small and they won't fit in the former. Plaster of Paris moulds absorb moisture and go mouldy unless you take extra car of them
 

I laser cut a whole bunch of stencils from mylar, these are going to be used in classes to teach airbrushing for cakes. I created artwork and ran them through the laser, I learned about how small details disappear and how deceptive it is working at zoom levels in inkscape. 12 sets were made in total and packed into bags.


For the fairy scene the image was broken into small parts so that it can be built up into a full picture. There are too many stencil islands on something like the dandelion so the main stem is made first and then a dozen seeds can be added after.


Once the brick wall has been painted there is going to be some graffiti added afterwards. This Wham sign has some simple bold colours but there is a lot of detail in the black sections. The star outline can be done in a single stencil but the word outline needed to be split into two separate stencils, one for the top half and one for the bottom.


Once the first graffiti was done, the second one was much quicker. I had worked out the kinks and how the lettering needed to be split so this was just a matter of following the same process.


by noreply@blogger.com (Martin Raynsford) at 01 November 2017 10:39 PM

30 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

Wooden Toys


The laser is good for personalising any item, this pull along toy made of wood is a prime candidate. There are a whole range of toys that could be done like this perfect for little ones.


by noreply@blogger.com (Martin Raynsford) at 30 October 2017 11:17 PM

29 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

PU Purse


I had a visitor come round and look at my laser cutters, he also bought some samples with him to see what could and couldn't be engraved. It's always fun to find new things to go in the machine. This purse was made from Poly Urethane, I set the power light and the speed fast and it lightly marked the surface, it's subtle but effective.

by noreply@blogger.com (Martin Raynsford) at 29 October 2017 11:11 PM

12 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

Vacuum Bed


The vacuum former came supplied with a wire mesh in the bottom of the bed. This lifts the item you're forming off the bed stopping it from blocking the vacuum hole. I decide to make myself a new vacuum bed that fills the area snugly and has a more uniform arrangement of holes. Thankfully the laser cutter is very good at making sheets of holes. I cut it out of 5mm acrylic, a sheet full of holes was held aloft on smaller dots that allow plenty of air flow under it. My thinking was that although the acrylic will eventually warm up I'm only heating the plastic for a minute or two and the plastic sheet provides a perfectly smooth surface. I was wrong, after I vacuum formed half a dozen items at once the sheet ended up pretty flexible and started to warp so I ended up remaking the whole thing in 6mm mdf instead. That's currently working very well but if it shows signs of degradation I'll just send off to have one laser cut in metal instead.











by noreply@blogger.com (Martin Raynsford) at 12 October 2017 08:37 PM

Hummingbird Protoype


I was inspired by the Colibri Hummingbird Automata to make this flapping wing version of my own automata. The flap isn't quite so good but the mechanism is a little simpler and it will suffice as a prototype for now.





by noreply@blogger.com (Martin Raynsford) at 12 October 2017 09:59 AM

09 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

New Tool: Vacuum Former


About 2 months ago I was talking about getting some parts vacuum formed so I had a quick look on ebay to see how much vacuum formers were and found one very local that was going cheap (comparatively). It needed to be gone by Monday morning, I found it Saturday morning, and it was a big industrial beasty that would probably need a van with a tail lift to move it. A few quick emails/phone calls later and I'd booked a van, spoken to the sellers, found a friend to help and things were all set for Monday morning. I'd gone from thinking about vacuum forming parts to owning a machine in the space of a few hours.

Moving day was fun, the machine is indeed big, heavy and very industrial. The machine had been unused for a while and the previous owner had it wired directly in to the wall because high currents kept blowing fuses. It was fair to say I was nervous about what I'd just bought but worse case I could just sell it again on ebay (and not being in a rush I would probably make a profit on it with a proper auction).

I ignored the warnings of the previous owners, whacked a plug onto the loose wires, ensured I had a 13A fuse fitted in the plug and connected it directly to the wall. The machine crackled into life literally, the heating elements were getting warm and making plinky plunk noises. The heating tray slid nicely back and forth, the lift mechanism was good and it seemed to form a seal around the plastic sheets. While we were out collecting the machine some plastic sheets had arrived and I was ready to vac form something. Thankfully I had a laser cutter to hand so could quickly and easily make a mould.

It's a sad design but if I'm going to be posting photos to you lot then I might as well remind you who I am. I fiddled and faffed with multiple sheets of plastic, cursed at failed attempts to pull a mould, discolouration of overheated plastic and ultimately came up with something that vaguely looked like the mould that was under it. The plastic is clear 0.5mm PETG, if you heat it up too much it turns milky white, if you don't heat it up enough it doesn't pull down over the mould.


Success, or at least enough of a success that I couldn't return it to the seller with complaints about it not working. The machine was functional, I had questions about the effectiveness of the vacuum pump but sorting all that was just down to my skill and time so it did nothing else for a bit. It takes up a lot of space in the garage and it took a week or two to jiggle things round and find it a new home (This was also the time I decided to lay the wooden floor). 



With the vacuum pump not performing particularly well I was still hedging my bets on reselling it. I showed a few visitors and then while I was explaining my woes to my father in law he reminded me that he actually works with vacuum pumps. A quick hour climbing around under the machine he had pulled the pump apart, checked all the pipe seals and given it a thumbs up. He also noted that cleanliness is very important and any piece of grit around the plastic seals would allow air into the mould. All the lips and edges were sanded free of grime and wiped clean, the next pull would be as good as it gets and determine the fate of the machine.


A vast improvement, there's life in the machine after all. The machine was staying, the rest was all down to my ability and with vacuum forming jobs already creeping out the woodwork it wasn't going to be long before it was earning it's keep.

by noreply@blogger.com (Martin Raynsford) at 09 October 2017 09:40 PM

07 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

Skulls and Engraving


I have recently been inspired by the work of Diego from the Engravers Dungeon (brought to my attention courtesy of the Laser Cut Stuff blog). He's been doing some amazing engraving of custom artworks, he's really managed to bring out the best of the wood using different colours but what really caught my eye are the two significantly different colours of laser cut. The large areas are engraved to create the typical 'brown' engraving where the wood grain can show through. The details however have this amazing 'black' engraving effect, he's understandably protective of his methods but it got me thinking about how it's done.


The laser cutter has 2 main modes of operation it can trace out a shape and cut it out or it can engrave an area where it moves over every 'pixel' within an image and puts a single dot onto each spot. Fancy laser cutters are able to vary the power of this spot to produce greyscale images, the Leetro controller (what I have) is only capable of doing on/off engraving. The burn mark is either full power or off, this produces the 'brown' engraving seen here.

There is technically one other option with the laser that I love and have used to great effect many times before. I use it for Line art, it's a cut operation but with a very low power that only marks the surface of the material without cutting all the way through it. This would appear to be very similar to what is happening here, large areas of seemingly 'black' engraving. The stuff I have previously done is much more for outlining objects but I thought I'd give it a try anyway.


First things first, I needed a suitable image to work with. I showed Diegos work to some of my friends and one of them told me that Vesalius made some anatomical drawings that would work well in this style. A quick search led me to some works of his that were recently digitised, 5 minutes on there and I had some suitable skulls to work with. I vector traced the first one and cut it (image above) and it kind of works. The skull was painted white, the brown areas are engraved and there is lots of line artwork that is starting to look correct. It works particularly well when the lines are close together but it fails on the big gaps, I needed some method for filling the gaps.

Normally when I want to engrave in greyscale I have to convert the image with a halftone effect, this varies the dot densities to produce a grey engraving effect (like how newspapers used to work). More dots make a darker area and a pattern like this fills the whole area so would be better for this line art. I converted the original image using a halftone plugin for paint.net, most raster editors have a method for doing something similar and GIMP is my suggestion if you're not using windows.


If you zoom in to the image above you can see the lots of little dots that make the image appear grey. It was natural to assume that if I drew around each of these dots I would get a similar half tone effect but done with 'black' engraving rather than 'brown' engraving. I imported the image into Inkscape and traced the image which left me with vector artwork for a halftone image. I set this up to be a very low power cut and gave it a whirl. (svg here)


As you can see the result is very effective, as a proof of concept goes it is definitely one method to achieve these kind of results from any laser cutter. The engravers dungeon clearly spends a lot more time waxing, oiling and finishing their artwork which accounts for most of the difference. I love their final pieces and am seriously tempted to own an original.

This isn't the end of the story though, if you look closely at the piece I created it looks very badly burned. Where the lines are close together it acts like a normal engrave cutting the whole area away and it looks a mess. There are many different methods to create halftone images so there are probably other ways to get the base image. As an Inkscape user I'm keen to keep everything in Inkscape so I followed this tutorial in order to make a halftone image using tiled clones. I have to admit it wasn't the easiest thing to do, the tool seems to max out at 250,000 clones (500 x 500) and it takes a long time to do but I persevered and created an appropriate image.


This image is full of little circles that don't overlap. My thinking was that they might be dense but at least the machine won't be cutting the same location over and over. Inkscape runs on a grid pattern so next time I would rotate the image 30 degrees before converting it so that the output is less 'griddy' (rotate the output back again before cutting). The result looks very effective from a distance but very 'digital' close up. (You can also see I keep adding embellishments with every cut). (svg here)


This is the point where I got carried away and shared my intermediary success with the laser engraving and cutting forum, received a dozen requests to show my workings and ended up writing this blog post (wordy for me I know). There are more things I want to try with this method....

1. This halftone effect would probably work well, instead of lots of dots the noodle shapes would outline well.
2. It is apparently possible to make halftone images using filter methods in Inkscape these look like they would create more suitable images for engraving.
3. The Eggbot from Evil Mad Scientist using hatch filling to colour in regions on their pen plotter, this would be another way to fill a region and worth investigating.

Finally the main reason my 'black' engraving looks horribly burnt is because I have a 100W laser cutter than doesn't offer particularly fine control at the low end. If I had an RF tube like Diego I would have better control over the beam power. The Glowforge laser cutter is also showing great potential for this kind of line artwork, sadly it looks as though they're about to announce another long delay on international shipping otherwise I would have mine already and I'd be able to try it out (2 years delayed and waiting)



by noreply@blogger.com (Martin Raynsford) at 07 October 2017 09:05 PM

Trays and bases


From my little bits of wargaming experience it appears that each of the models sits on a small base which needs decorating which can be done with little disks and there are trays to move whole units of models around at once (even if just for display). My idea was to combine those two things together and make bases and trays where the pattern continues, as though the whole unit were on a marbled floor. Not sure if this is a desirable thing, let me know.

by noreply@blogger.com (Martin Raynsford) at 07 October 2017 09:22 AM

06 October 2017

Martin Raynsford hackergotchi for Martin Raynsford

Grasshopper Costume



Eli wanted to dress as the Grashopper from James and the Giant Peach to celebrate Roald Dahl day at school this year. We put together a paper mache mask based on a balloon and cut about to achieve the desired shape. He's very slowly writing an instructable about the process but I thought I'd include it her for the meantime. We did laser cut a monocle for it, which either counts as overkill or finishing touches. He was very happy with the finished result and I got to play with my new airbrush for various paint effects.



by noreply@blogger.com (Martin Raynsford) at 06 October 2017 06:56 PM

Squad Racks


Another wargaming build, it amazes me how much variation there is in the way of trays and arrangements and models. It's no wonder there are dozens of companies already doing these things and yet people still ask me for something different. These 25mm trays have a hole in the bottom for a 2mm magnet which helps the models stay in place. 5 slots holds a single squad at a time. (svg here)






by noreply@blogger.com (Martin Raynsford) at 06 October 2017 09:09 AM

02 October 2017

Gareth Howell hackergotchi for Gareth Howell

Never underestimate the power of a fridge magnet.

Last Friday, I went to the ACE Study Day ‘Aspects of Publishing: Guide and Souvenir Books’ at the Geffrye Museum. We’re in the process of redeveloping our guidebook at work, and it was interesting to see how other organisations and museums had come to their decisions about the kinds of books they produce, and who they are for.

It was great to hear people speak openly about what had and hadn’t worked in their institutions, and how they dealt with external factors, such as placement within their shops and ticketing areas, and the ways that staff help sell them as part of a visit. It was also interesting to hear people speak honestly about the tensions between commercial and curatorial needs within the institution, and the strategies for overcoming them. The title of this post comes from a response to a question about the needs of museum shops to ensure they make money while maintaining the voice of the institution.

The range of publications was wide, and raised a lot of questions about where we might go with our guidebook, what its function might be, and who it is for:

  • Does it need to act as a guide? Is its main function to help guide people around the exhibition and interpret the pieces on display? Does it need to contain a map? Is the intention that the book is used while at the centre?

Our current guidebook has a spread for each of our galleries, with key objects to see, as well as a map, and information about our other business activities, such as Education, Venue Hire and Weddings. We were shown examples of books which offered ‘A quick look’, and ‘containing 10 trails’, which were specifically intended to guide the visitor on the day.

  • Does it need to focus on the collection and exhibits? Should the book be specifically tied to aspects of the collection and the exhibits we have in the space, or should it be used to open up wider themes?

In the case of the Space Centre, could we use impressive images from Hubble or NASA’s archive to frame themes we address in the exhibition, rather than focusing on objects we hold or display? This potentially gives the guidebook a longer life, as the exhibition changes over time.

The National Trust recently published Prejudice and Pride, which celebrates and focuses on LGBTQ Heritage across the National Trust sites.

By focusing on a theme in the context of British heritage, the book is not a guide to a visit, but rather a resource that reflects on hidden or previously untold histories as part of a wider discourse on heritage and what that means.

  • Who is it for? Should the guidebook be aimed at the reader who wants more in-depth information to supplement their experience at the centre? Should it be a visually led document that triggers memories and discussion about the visit? Is it aimed at all visitors, or targeted at a specific reader? Is it for kids?

Our current guidebook is a mix of all of the above, which over time (and with incremental changes) has become a tangle of information, voices and intention. One of the triggers for this new redevelopment has been the recognition that we need to focus the guidebook and ask who and what is it for.

  • Do we need more than one? Does it make sense to divide the guidebooks into separate smaller pieces which can appeal to different readers, uses and price-points?

We were shown great examples of institutions’ range of books, from text-heavy interpretations of the museum, to pocket-sized books selling at £5, to kids’ activity books, which were created in response to audiences needs.

A great example is the National Portrait Gallery’s 100 Portraits book, which is small (150mm x 150mm), image-focused paperback, and retails for £6.95. It sits within a range of other publications from the National Portrait Gallery and is the kind of thing that would make a great gift or souvenir.

As we approach our new guidebook, these questions will help us form our ideas and work out the best way forward. I’m hoping that eventually we will develop a range of books which enable us to tell our stories in different ways and appeal to different audiences with a credible and confident voice.

by Gareth Howell at 02 October 2017 02:52 PM

Martin Raynsford hackergotchi for Martin Raynsford

It's Alive! Frankenstein Cake


Continuing my work on the craziest cakes ever, Dawn and I recently made this Frankenstein cake for the preview night of Young Frankenstein at the Garrick Theatre. After I faffed around with various lifting mechanisms for a while I ended up buying a large linear actuator from ebay, it's probably overkill but the weight of cake really adds up after a while. I made the arms detachable which is easier for icing. The knife switch actually controls the motion, it's a double pole double throw so flipping it over changes the direction of the motion. Dawn from Dinkydoodle Designs did the hard part of covering the whole thing in cake and presented it to the cast and crew.









by noreply@blogger.com (Martin Raynsford) at 02 October 2017 10:24 AM

27 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Little wooden box


I made this little box as a bit of a distraction this week. I wanted to test some hinge designs again and although this has been done by lots of other people I haven't tried it before. The circular disk in the hinge allows the lid to rotate around a point, not in the centre of the material, and once stood upright the lid rests on the back wall of the box. This style could be used to stop it rotating all the way back on to itself. It didn't quite fulfil all the things I wanted from it but it gave me some new ideas about what to do next. (svg here)



by noreply@blogger.com (Martin Raynsford) at 27 September 2017 05:25 PM

25 September 2017

Gareth Howell hackergotchi for Gareth Howell

Back to School!

I’ve just signed up for the Museum Association’s AMA professional development scheme. I’m really excited about the programme, and looking forward to developing new directions and ideas over the three years. I’m also excited to be able to have a framework to support critical reflection and looking beyond the everyday demands and restrictions of the space I work in.

I’m currently working as Exhibition Designer at the National Space Centre. I’m not sure it’s the same for everyone who has a similar role, but it’s one I’ve found my way into, rather than having a defined career goal from the start. I started out after university making visual art and performance before getting excited by web design in the 90’s, and via a wiggly path involving digital arts projects, horror film festivals, motion capture, teaching, and performing as Britney Spears at Glastonbury, I joined the National Space Centre as a web designer in 2011. Through luck and meeting some great colleagues, the role has changed over the years, and these days I’m mainly designing spaces, interactives and graphics, as well as being involved in the Exhibition Leadership Team.

I don’t think it’s necessarily a bad thing to have had such a varied work history. The transferrable skills, approaches and ways of thinking are all valuable things to have, but I’m not sure it’s consistent, and it makes me anxious that I’m missing fundamental experience and understanding of aspects of the Museums and Visitor Centre sector.

I’m also, to be honest, not entirely sure what Exhibition Designer means! Should I be writing and proposing stories and treatments for the galleries and the visitor experience? Should I be walking round with a pencil behind my ear, or heavy rimmed glasses and a turtle neck jumper? Should I be providing detail drawings and material lists to contractors? Should I be writing interactive software, or briefing someone else to do it? Should I be researching audiences, trends and new ways to engage visitors? Instinctively, I think it’s all of these things, but I’m aware that as I look around at jobs with that title, it’s sometimes a tiny, specialised bit of that list that people are looking for, and sometimes all of it and more!

The National Space Centre opened in 2001, and in some places, you can really tell! That’s no criticism, it’s the reality of any museum or exhibition space. Knowledge develops and changes, stories gain or lose relevance, audience expectations change, and parts of the exhibition begin to look dusty and dated. We are lucky to have an exhibition team in-house who can continue to refresh and redevelop the centre, whether replacing a damaged graphic or reimagining a space to communicate an idea better, or to allow our visitors to experience it in a new way. As a team, we are developing new ways to make the exhibition more accessible, inclusive and participatory.

I’m lucky that work is giving me the time and space to work on the AMA, and to be part of a team that values the need for research and reflection. I’m looking forward to asking the tough questions about what my role is and should be, and what the National Space Centre is and can be. I’ll be posting my thoughts and questions here as I go (I’ll tag them as AMA), it would be great to hear from you!

 

by Gareth Howell at 25 September 2017 05:32 PM

22 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Coaster Jigs


They may not look like a lot but jigs like this can be pivotal to the success of a large project like the 100 coasters I made yesterday. If you're going to be doing anything 100 times it's worth spending a few minutes considering how you can make each step smoother to cut down on assembly time. Here are just a few questions you want to think about and if you answer 'Yes' to any of them you probably want to make yourself a jig. Thankfully the laser cutter is particularly good at making jigs for parts as well as the parts themselves.
  • What is the most efficient order for assembly?
  • Do parts have to be specifically aligned to each other?
  • Where does the glue have to go and are there places where the glue shouldn't go?
  • How do you remove the part from the jig once it is assembled?
These coasters break down into 2 parts of 3 layers each. The inner triangle has a middle layer that is smaller than the outer layers, this means it needs to be aligned perfectly in the centre and because it is on the reverse side of the cutting we can't just draw registration marks.


The first jig is designed for gluing the middle layer to one of the outer layers. It is a stepper tray, the smaller piece sits right at the bottom and the larger piece sits on top of it, the two parts are held in position until the glue dries. The glue is applied to the smaller part, this is because we don't want any overflow around the edge of the larger part, applying glue to the smaller side means that it is going to stay between the two pieces. It was easiest to run all these parts together in a single batch of 100, this means the glue will have dried before we try to use the part again in the second jig. 


The second jig holds all the pieces for final assembly. The outer square is built up in 3 layers again but the middle layer is thinner this time to allow it to sit in the groove around the edge of the triangle. 
The newly glued part is aligned in the middle of the jig by a corresponding 'V' shaped layer, this just squares the piece up and ensures it isn't in the way of the outer layers. Glue is again applied to the narrow bottom layer to glue spillage and the middle layer is installed as 4 separate pieces. These pieces overlap onto the triangle. The top layer is glued down to form the outer frame work and finally the top triangle is glued into place (and aligned by eye) to secure the triangle into the frame. The newly formed coaster can be poked out of the jig using the hole in the bottom. The whole process took about 3 minutes.

by noreply@blogger.com (Martin Raynsford) at 22 September 2017 01:11 PM

21 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

100 Coasters


I had a pretty busy and productive day yesterday assembling these coasters. They're now headed off into the post with the hope that they'll arrive in Edingburgh for an exhibition at the weekend. 100 coasters in a (long) day is not bad work at all.


by noreply@blogger.com (Martin Raynsford) at 21 September 2017 01:05 PM

20 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Tool Key Ring


Basingstoke Makerspace recently asked if I would be able to modify the design of the Reading Hackspace tool key ring to include their logo (a small piece that they use to demonstrate the lasers capabilities). It was a simple task but I thought I might as well cut one at the same time. The Hershey text containing the URL is perhaps a little bit small but I was impressed that the laser picked up all the details.

by noreply@blogger.com (Martin Raynsford) at 20 September 2017 11:01 PM

19 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

More Vale Runes


Once you take shiny things to a LRP event people start to realise how useful they can be, the trouble is that everybody really needs something different so they can identify it as their own. Wood dyes have been extremely useful to reproduce these sets of vale runes. Everything else is the same really but the wood was dyed before being cut so they end up looking quite different.

by noreply@blogger.com (Martin Raynsford) at 19 September 2017 01:15 PM

17 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Hidden Messages


I made these story disks for Vale, each one has an encrypted message spiralling around the disk from the inside out. The encryption is made even harder by the fact it is displayed in the vales own font, 26 runes representing the 26 letters of the alphabet.

by noreply@blogger.com (Martin Raynsford) at 17 September 2017 05:01 PM

15 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Vale Box Comission



I love how the laser cutter allows me to make the same thing but customised and ever so slightly different. This is the same vale box that I've made twice before but I tweaked it and put a different cover on the top. Each iteration gets me an easier build, takes less time to assemble and recoups some of the time investment, I'm always happy to take on more rebuilds.



by noreply@blogger.com (Martin Raynsford) at 15 September 2017 05:28 PM

14 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Stat Counter


After making the other types of counters recently I was asked if it was possible to make a small counter that tracked 5 stats at once. I gave it a good effort but it's a little bit small and fiddly to use at this scale. I may take another shot at it to see if I can make it more useable but there isn't a lot of room left in that base





by noreply@blogger.com (Martin Raynsford) at 14 September 2017 05:17 PM

13 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Quick stencils


I needed a set of stencils for painting onto fabric, thankfully I had some mylar on the shelf and I was able to create these really quickly.

by noreply@blogger.com (Martin Raynsford) at 13 September 2017 05:12 PM

11 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Leicester Guildball Markers


I've been making a range of items for the Leicester Guildball Group recently because I'm local and have a laser cutter. It's all fairly standard stuff but it's nice to see people using the things you make.



by noreply@blogger.com (Martin Raynsford) at 11 September 2017 09:44 PM

08 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Best Ever Wood Glue


I make a lot of things out of wood because it laser cuts incredibly well, it's cheaper than plastics and you can glue it together. I've tried quite a lot of glues and I really like this Weatherproof Exterior glue from Evo-Stik. I've been buying it in smaller bottles with applicators but recently discovered that Rapid Electronics sell it in 2.5 and 5L bottles, suitable for refilling all of my smaller bottles. The glue grabs within a few minutes and sets solid and clear overnight, I'd definitely recommend getting some.

by noreply@blogger.com (Martin Raynsford) at 08 September 2017 09:44 PM

07 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Exhaust Fan Upgrade


My extractor fan always sat at an awkward angle where the inlet needed to be on the wrong side and the outlet was best pointed vertically. I previously achieved this using some shelving brackets but it was always a bit wobbly. While I was laying the floor I noticed that they were bent and the whole thing was touching the floor so I upgraded to this wooden stand instead. The fan is now held firmly in place again, better than ever before. The whole thing tucks in neatly behind the new machine in the garage.


by noreply@blogger.com (Martin Raynsford) at 07 September 2017 07:48 PM

05 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

New Wooden Floor


The floor in the garage was just sheets of plywood which has served me very well over the past few years but it was starting to look a little worn. In my week off I laid a nice new wooden floor over the top of it. It was fun juggling all the stuff from the front to the back of the garage and finding it all new homes but the floor is in at least and looking good. I still have to sort all the junk that got moved up onto the shelves and hidden around the house but it's a good start.




by noreply@blogger.com (Martin Raynsford) at 05 September 2017 08:17 PM

Gareth Howell hackergotchi for Gareth Howell

BSA Scientist Top Trumps

I’ve just finished working on a set of Scientist Top Trumps for the British Science Association : Brighton and Hove Branch. They were launched on the 5 September, as part of the British Science Festival 2017, with different cards being placed in venues across the city, encouraging collectors to visit the different spaces and take part in the talks and activities there.

It’s been a really fun project to work on, and it was great to have the opportunity to work with the BSA. I really liked the diversity and range of scientists who were featured, and enjoyed reading their stories. The colours and fonts were chosen to fit the BSA branding guidelines, and I made an icon pattern for the back of the cards. The portraits were found on Wikipedia, with the background headers coming from stock, or public domain libraries.

Here are some of my favourites. If you’re out and about in Brighton, try to collect the set!

 

Henrietta Swan Leavitt CV Raman Grace Murray Hopper Percy Lavon Julian Katherine Johnson Max Planck

by Gareth Howell at 05 September 2017 06:51 PM

04 September 2017

Martin Raynsford hackergotchi for Martin Raynsford

Keeping the laser busy



I have a few relatively big cutting jobs to do over the last few weeks. They keep the laser busy while I'm free to answer emails, sort paperwork and all the other boring jobs that occur as part of life. Hopefully many of you will have noticed the not so subtle changes happening to the blog too as I try to get this sprawling monstrosity of 1200 posts into slightly better order of things. I'm not allowed to mention most of these projects yet but the posts are written and waiting for specific dates.

I have however been cutting some more Hex Terrain Toolkit which seems to be a very successful project for Ross.


by noreply@blogger.com (Martin Raynsford) at 04 September 2017 07:51 PM

31 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

More Wound Counters


These white on black counters were much simpler than the others. The actual numbers on the dial still had to be done with a paint infill but the actual symbol and lettering was engrave so they show up white enough to not need painting.

by noreply@blogger.com (Martin Raynsford) at 31 August 2017 09:52 PM

Gareth Howell hackergotchi for Gareth Howell

Eden: Journey into Space

Earlier this year, I worked with the Eden Project on their new summer holidays exhibition, Journey Into Space. The exhibition formed their summer programme, and included an Alien Encounter, Astronaut training, a Solar System Safari and a VR Theatre, alongside talks and activities.


 

The key areas we were involved in designing were the Solar System Safari, and the VR Theatre.

The Solar System Safari is a walkthrough exhibition which takes the visitor through the Solar System, starting from the Sun and returning to Earth at the end of the journey, via ten interlinked spaces. Each space in the exhibition uses elements of sculpture, lighting, audio and video to give the viewer an experiential view of the planet or Solar System object.

The process of working with the team at Eden involved collaborating (mostly remotely) to fix ideas, scope the needs of the individual rooms and to design the piece to make a coherent journey. It was important that each room gave the viewer a different experience, and that the story of returning to Earth was key to the exhibit.

Our initial process involved using Mural to throw together visual ideas and inspirations. The advantage of using Mural, especially in remote meetings was the potential to update live and add new elements as they were discussed. From this early collaboration, we were able to map out the space, and to begin to design the elements of each space.

I mapped out the space in Sketchup, which allowed us to get a real sense of the space, and to begin to work out the sizes and technical needs for the projections, as well as the set elements.

Our team at NSC Creative was responsible for creating the media elements for the exhibition, which included an animated Sun, volcanoes on Venus, a Pepper’s Ghost projection of Saturn, and a five screen animation of the Earth as seen from the ISS.

On-site install.

In early July, Kyle and me headed down to Eden to spend a week installing the media and helping to get the exhibition ready for opening.

The Solar Safari is built on the stage area of Eden, a temporary exhibit space which is used for Eden Sessions, holiday exhibits and special events. This meant that the exhibition was installed in a week, from start to finish! There was a large team working throughout the day to build, install, troubleshoot and tidy the space. The atmosphere was great, and the team was fantastic.

It was great to see the exhibit forming around us, and to be involved in such a concentrated burst of activity.

Painting the Sun Kyle in a cave Mars surface ISS in progress Backlit Milky Way Ceiling

It’s been an honour to work on such a large and fun project, and to spend time working with the team at Eden. It’s been great to see people’s reactions to the project too!

 


by Gareth Howell at 31 August 2017 02:17 PM

30 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Paint Infill Experiments




I read on the internet about a few different techniques to infill acrylic with a different colour. I've done some previous painting where I engraved the protective cover off the acrylic. I found that engraving that protective sheet can be a bit hit and miss, sometimes it engraves fine but other times it just appears to melt so I prefer to peel it off now. I tried to apply some vinyl transfer tape which engraves better, this was effective but it seems silly peeling off one sheet and applying another.

I settled on a compromise between the two. Since all the numbers and words around the outside are cut using Hershey text, instead of engraving they cut cleanly even through the protective sheet. The engrave in the middle of the item is done by first outlining the engrave with enough power to cut the sheet and then peeling the sheet off from the place that's going to be engraved. The idea is to do it in a single piece so they will be no weeding, the engrave can then be done in the gap that remains. The item can then be painted and once dry you can peel the mask off and you only need to clean up the engraved area.


by noreply@blogger.com (Martin Raynsford) at 30 August 2017 09:41 PM

29 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Wound Counters


I was asked to make some wound counters for a war gaming friend, the counters need to go up to 30 and still be a sensible size so I based them upon my Tigris Counters. I didn't want to use magnets in the middle though so I ended up gluing the parts together instead. They work well. 
I used white acrylic paint to provide high levels of contrast on the lettering and image.





by noreply@blogger.com (Martin Raynsford) at 29 August 2017 03:10 PM

24 August 2017

Gareth Howell hackergotchi for Gareth Howell

Freeze Tag

Karen Forever

by gareth at 24 August 2017 06:47 PM

23 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Tablet Weaving 2


I recreated these tablets with a different image by request.
I've also been working on some acrylic with paint infill experiments recently so expect me to post about those shortly.


by noreply@blogger.com (Martin Raynsford) at 23 August 2017 10:28 PM

20 August 2017

Iain Sharp

The “Electronics Kit” Common Emitter Amp

One project that’s been in my mind for ages is to revisit some of the circuits from my childhood Philips X40 kit. I finally got around to putting “Experiment 5 – Telephone pick-up and amplifier” in to my circuit simulator. This is the first of several audio amplifier circuits in the manual, and they all follow the same design pattern. Similar circuits are also used in other educational kits. I had tried to use this circuit design in my own electronics experiments as a kid. Mostly it didn’t work, but sometimes it did. As an adult, I was interested to understand its characteristics to help explain where it’s appropriate.

View the about in full screen.

Looking at the simulation you will notice the amplifier is non-linear (compare the shape of the top of the sine wave out to the bottom in the output of the first stage). This isn’t unexpected given that transistors have an exponential relationship between the base voltage and the collector current. The biasing on the second stage also looks bad, meaning that the output signal is clipped on the positive side. The simulation result raises several questions in my mind:

  • Why is this type of amplifier so popular in basic electronic kits?
  • Are they circumstances in which the amplifier is linear?
  • What are the characteristics of this type of amplifier anyway?

To answer these questions, let’s look at the basic building block of this amp. It’s a single transistor common emitter configuration. The biasing is from a high value resistor between the collector and the base. Wikipedia informs me that this configuration is called “collector feedback bias“. The signal is coupled in and out of the stage through capacitors.

Single Stage of Amplifier

Looking at this circuit you can guess why it’s popular in these kits: the component count is very low. Hence, it is easy for kids to build. If you have an intuitive understanding of transistors, you might also guess that resistor between the collector and the base creates negative feedback giving the circuit the ability to find a suitable operating point across a range of conditions.

As all the textbooks tell you, transistor amplifiers require that the transistor(s) are “biased” correctly to work. The aim of biasing is to set the DC conditions around the transistor so that it is in the “active zone” of operation. The active zone means that you are past the threshold for the base voltage required to start to turn the transistor on, but not yet at the base voltage where the transistor is fully turned on and saturated. The DC conditions that the biasing establishes are called the “operating point”.

As I mentioned, in this circuit the base resistor provides negative feedback which tends to stabilize the operating point. When the circuit is switched on there is no current through the transistor so the collector voltage is at the power supply voltage and the base is pulled high though the two resistors. This rising base voltage turns the transistor on and this pulls the collector voltage down (because of a voltage drop through the collector resistor) which in turn reduces the base voltage – tending to turn the transistor off and reduce the collector current. In practice, these effects will almost instantaneously reach equilibrium with the transistor in a partially on state – i.e. in its active region.

Wikipedia gives a pretty good explanation of how to calculate the operating point so I won’t repeat it. One thing to note though, for the resistor values used in this configuration, the operating point will depend on the gain (β) of the transistor so the operating point will change for different transistors. Here is a graph showing how Vc depends on the gain (β).

Theoretical Vc (Y axis) Vs Gain (X axis) for Circuit Shown Above

So, that just about wraps-up the situation for the DC bias. It works just about OK as long as you aren’t fussy and don’t expect a big output voltage swing I guess! What about the AC characteristics of this circuit? What is the gain? What about this non-linearity effect?

I checked a few standard text books, and the web, and couldn’t find a theoretical treatment for this circuit configuration so I had to come up with my own. Let’s start by assuming that the impedance of the input source through the coupling resistor is low compared to the input impedance of the amplifier. In that case the input signal becomes just a change in voltage on the base of the transistor (ΔVBE). In that case we can use the Ebers-Moll equation for the transistor to work out the impact on the collector current (and hence the collector voltage). Ebers-Moll says:

IC2/IC1 = Exp( ΔVBE / VT ) Where VT ≈ 25.3mV at room temperature

If you write IC2 = IC1 + ΔIC, and convert the collector current to the corresponding voltage you can get the solution:

ΔVC = ( 1 – Exp( ΔVBE / VT) ) . ( VCC – VC1 )

Where VCC is the power supply voltage and VC1 is the voltage at the collector at the quiescent operating point

That equation fascinates me for two reasons:

  1. Clearly, this is an exponential amplifier – which explains the non-linearity
  2. The gain depends on the collector voltage at the quiescent operating point. The graph above which shows how the operating point changes with β translates to changes in the stage gain.

Can we imagine this amp could be approximately linear? Well, as my high-school physics teacher said “everything is linear if you look at a small enough range” (cue sound of 1,000,000 mathematicians groaning). So, we know by Taylor expansion that:

Exp( x ) = 1 + x + x2/2! + x3/3! + …

So, if ΔVBE << VT we can approximate the exponential using just the first two terms above.

ΔVC ≈ – ( ΔVBE ) . ( VCC – VC1 ) / VT

In other words, for very small input signals (<< 25mV) it is kind-of, sort-of, a linear amplifier of gain ( VCC – VC1 ) / VT . Here are some handy plots from Mathics of gain Vs β, Rc and Rb.

Stage Gain (Y axis) Vs β (Top), Rc (Middle), Rb (Bottom)

Actually, the stage gain in this configuration is quite high, though very dependent on the β of the transistor. I might also remark that the output impedance is poor (limited by Rc ), though, without having done the calculation, I think the input impedance is probably OK.

So, if you want a high gain, single stage, small signal amp with very few components, and, you aren’t too worried about predictability of the gain OR linearity OR output impedance then this circuit just about does the job. This actually fits the bill for these beginner’s electronic kits pretty well. If your requirements are more stringent then better avoid this circuit and look for others. Just one thing still seems odd – why is the second stage bias set where it is on the original circuit?

For me it’s been interesting to look at how much information you can extract about this, fairly trivial, circuit and it’s certainly refreshed my understanding of transistor fundamentals. I hope you find it interesting too.

by Iain at 20 August 2017 06:43 PM

11 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Reuleaux triangle coaster


I was approached with a design for a coaster using a Reuleaux triangle in the middle. It is a shape of constant width so it is able to rotate within a square just like a circle would. I made some tweaks to the design like putting in a lip on the middle layer to stop the shape falling out. It works and is fairly functional but it's not very smooth and it squeaks as it turns, I've yet to come up with sensible solutions to those problems.


by noreply@blogger.com (Martin Raynsford) at 11 August 2017 09:28 PM

07 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Geometric Embroidery T-Rex


The T-Rex is the last of the Dinosaur range for the moment, I have the knack of drawing now and the style and also I ended up buying 36 embroidery skeins so I'm sure there will be lots more variation in the future. For now, here are the dino buddies, happily playing together.


by noreply@blogger.com (Martin Raynsford) at 07 August 2017 10:12 PM

06 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Geometric Embroidery Triceratops


Another embroidery dinosaur, this one was much quicker to draw and now that I've found an embroidery needle it was much quicker to sew (please ignore the snag on the back like I did :p). I'm pleased with these so I expect I'll be putting a set of three up in the store shortly.




by noreply@blogger.com (Martin Raynsford) at 06 August 2017 08:20 PM

05 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Geometric Embroidery Velocirapter



I think the title just about sums it up, I was looking at some of the Cotton Clara designs and I was inspired to make my own embroidery designs based upon dinosaur shapes. I think they'd make fun little kits for kids.



by noreply@blogger.com (Martin Raynsford) at 05 August 2017 07:55 PM

04 August 2017

Martin Raynsford hackergotchi for Martin Raynsford

Lasercut Sugar Cookies


In a slightly strange obsession I've developed I've started trying to cut some edible materials. I've cut gingerbread in the past and it works ok but it's a bit stinky. This was a sugar cookie recipe I tried. As you can probably see immediately there was a big crack appearing on the surface before I even started cutting. The laser seemed to go through it easily and a lot of smoke came out from underneath, a sure sign it cut all the way through, turns out it hadn't though. When I eventually broke the shape out there appears to be a seam running across the middle of the biscuit too which made it snap in half that way. A bit of a failure all round and it was still stinky and didn't taste very nice so time to move onto the next recipe.



by noreply@blogger.com (Martin Raynsford) at 04 August 2017 01:05 PM