Space Invaders Table

So... I realise that it's not so much that I'm lazy about doing any projects, I'm just lazy at writing up any thing.

And so it was that I was inspired by the light up coffee table on hackaday http://hackaday.com/2014/02/03/ikea-led-table-mod-doesnt-lack-awesome/ today.

Inspired to write up a project that I'd completed about three years ago.

I'll start by saying that this was not my idea, I was inspired to make the coffee table after seeing a similar table on the make blog, http://makezine.com/2008/11/11/space-invader-coffee-tabl/

This coffee table uses what look like regular 4 inch tiles (slightly smaller than the average bathroom tile [6 inches]) to create a mosaic table top, Of course old 8 bit pixel sprites lend themselves very well to being made into tables from normal square tiles. it (and every other table of this type I've seen) takes the option to tile the entire table top, all the way to the edges -I decided to inlay my design in the centre.


The tiles I used were tiny in comparison (to the 4" tiles), I used mosaic tile mats, these are 12" square mats that have lots of 1" square tiles stuck to them in a uniform pattern of random colours, Black, white and two shades of grey.

The first step is to remove the tiles from the flexible backing and sort by colour, -the tiles can be just pulled off the backing -or the backing can be peeled off the tiles which is probably the more accurate way to describe the process.

Next you need to get yourself a LACK coffee table from Ikea, one of the little 50cm square ones, I chose to get a back one.

You can choose to assemble the table, or just work on the top on whatever work bench you have.

Start by arranging your tiles in the pattern that you want, you could either look at a reference picture (as I did) or make up your own design. include all the spacing in your tiles that you intend to put between them (grout lines).

Now mark out (using pencil) a square in the middle of the table, -your tile size, and your intended tile spacing will determine tile size -measure your layout! (I used a pack of tile spacers, but with a 3d printer you don't have to use the off the shelf ones -you could print your own, or you could use matchsticks etc...)

When you have your work area marked out start with a large "Stanley knife" (box cutter) and a metal straight edge and score the lines in the table top.
A good tip (unless you're very good with the knife) is to start in the corners working towards the middle, this means that you won't drag the knife on the table top that will be left.

It is unlikely that you will be able to cut through the top in a single pass of the knife.

Once you have cut out your pattern shape you need to pull it out. this will leave a hole in the table, and leave you with your first challenges.

The challenges are:
That the table is not solid, inside the table is a hexagonal arrangement of cardboard. you cannot set the tiles on that cardboard. not the thin air in the hexagonal gaps.
Secondly
That the tiles are going to be around 5mm (1/4") thick, but the table top (hardboard/melamine type material) is much thinner.

To get around this you need to firstly trim down the cardboard (either using the knife of a pair of scissors) -don't worry about being too careful of the height that is left.

Once you're done trimming down the card you need a can of expanding foam insulation.
carefully squeeze a portion of foam (don't fill because it expands) into each of the hexagonal pockets.
the foam will expand to fill the pockets and slightly dome out of the top of them.

Now using a large flat serrated knife (bread knife) cut the foam so that it's about twice the width of a tile under the surface of the table top.

Spread tile adhesive in a layer on top of the foam. and using the plastic tile spacers, ensure that the gaps remain consistent. push the tiles into the adhesive such that the tops of the tiles are level with the table top.

Now leave the table another day or two for the adhesive to properly dry.
finally fill in the gaps (grout lines) between the tiles with tile grout.

The table I used was a black Lack table. cost £5
The tiles I used were two packs of kitchen/bathroom mosaic tiles (cost £2 each) -and I have plenty left.
Expanding foam I used cost £2 per can, only a small can is needed (whilst there is some left, foam sets in the nozzle making the can useless unless you clean it directly after use)
the tile grout I used was a grey glitter grout.

The final results are here:

Making an extension lead, (plug end)

I made a post last week about adding an extension lead socket to a length of wire.

Now I'm going to detail the plug end.


So start by looking at the pins, here you'll find two screw holes that secure the male plug pin part to the back cover that you hold whilst plugging or unplugging.

undo these screws and remove the back cover, then put the back cover onto the wire that you're using to make the extension lead, (or the flex for the equipment that you're attaching the plug to) so that you;ll be able to close the plug later once the wires are connectted.

Again, start by stripping your wire.
then cutting the phase wires slightly shorter than your earth wire, (so that if the cable is strained, your equipment would go dead before it became unearthed)

Now loosen the cable clamp and attach the wires to the plug terminals.

Finally clamp the cable in the cable clamp, push the back cover on, and screw it back into place with the screws that are next to the plugs inside the plug shroud.

Your extension lead is now complete.

Electronics lessons: Mains Power -single phase and three phase

Whilst writing this blog I've stayed away from things that I would consider dangerous.

That is to say I've completed some projects that I've felt were either too big to document, (like when I put up my new storage shed in the garden and put electrics and lights etc in.) -at the time my thoughts were like this. it's OK to tell someone to stick bits of wood together to make a speaker, it's OK to say to people use this step down transformer and deal with the safe voltage that comes out the other side. I even thought it fine to tell people to stick electrodes into water to generate hydrogen/oxygen gases!

But big scary voltages have been something that I've stayed away from, the thing about mains utilities is that, you can smell gas, and know to shut off the supply and get out. you can see water and hopefully have the intelligence to get out before drowning. Electricity is completely invisible, it's not a substance, it's a force.

Anyway, that might give you an insight as to how I feel about mains electricity. it's dangerous to the point of deadly, and too much confidence can lead to mistakes that ultimately can kill you.

As a point of reference I live in the UK, this means that for me, voltages come in 120v for site tools, (where the 120v is considered safer due to lower voltages) this voltage is obtained by using those little yellow transformer boxes.

240v comes into every homes, (at least every connected home, I suppose off grid homes might make their own standards).

440V is considered industrial and is what most three phase power outlets are going to be using.

Voltages are measures with respect to neutral, live - neutral.

Single phase

Single phase power is an alternating waveform going from the positive extreme of the voltage swing to the negative extreme of the voltage swing in one wave form.

Single phase is what I've mostly dealt with, it's easy to visualise, easy to look at and easy to understand. remember that the positive is measured with respect to neutral, not with respect to ground.

Sometimes a single phase supply is actually a 2 phase supply, where instead of a virtual earth, or earthed neutral, there are two hot phases where the phases are 180 degrees apart.
the sum of the phases is zero, (e.g at 0 degrees phase 1 is 0v, phase two is at 180 degrees and is also 0v, at 90degrees, phase 1 is +120v and phase two is 270 degrees and -120, (+120 + -120 = 0v), the total potential difference between the two phases is 240 volts, (120 - -120 = 240)

Three phase

Here's where it starts to get a little more complicated.
Now there are three phases, each phase is 120 degrees behind the next, they are still sine waves, and they are still measured with respect to neutral, but there is no neutral in the transmission line, -when power enters your premises in a single phase set-up there is a live and neutral line. when you get three phase there is only 3 live wires, no neutral. (you can make a neutral by connecting all the phases together, because the sum of the phases is zero) -but I'll cover that in a later lesson.

You can see at 90 degrees now phase 1 (blue) is at at the top of it's rising cycle 240v, and phase 2 (green) is just coming up from the bottom (so during it's rising cycle) and is -120v, whilst phase 3 (red) is getting towards the bottom of it's falling part of the cycle, and is -120V
240 + -120 + -120 = 0

Colour Codes

Colour codes for wires are important, in that they will let you know what wire does what. everyone knows that green/yellow stripe is earth, and it's safe to touch. but what if I wired a plug so that the earth wire was used as a live conductor.
it's just a bit of copper, fundamentally there is nothing to stop me from doing that, provided I wire the other end the same way, where's the problem?

The problem is what happens when I'm out, and whatever appliance I've wired badly breaks, what if my wife/girlfriend/boyfriend/husband/friend/son/daughter/mother/father/grandparent etc decides that they just want to check the fuse on the plug, then they see the wires connected wrongly, so think that might be the problem. or something see's an earth wire, and decides that they can splice that wire to earth something else, -except it's not earth, it's live, and they are probably now dead.

Colour codes are set by the IEE.

for single phase systems.
Brown = Live, (the old colour was red)
Blue = Neutral, (the old colour was black)
Green and yellow stripe = Earth, (the old colour might be plain green)

for three phase systems,
Brown = Phase 1 (old colour was red)
Black = Phase 2 (old colour was yellow)
Grey = Phase 3 (old colour was Blue)
Blue = Neutral (old colour was black)

This means that if you are adding new wiring to an old system, don't just connect the new blue wire (N) to the old blue wire (P3), or the new black wire, (P2) to the old black wire (N)

you may also find three phase systems where the conductor colours are Brown, brown brown for P1, P2 and P3, with a blue for earth.

Earth (as always) is green yellow stripe.

earth may also be the bare wire in fixed installations, (where solid core wire is used rather than stranded wire).

Making a new hotend heater

Annoyingly my replacement hot end for my solidoodle has failed again. it did last a lot longer than the original hot end that came with the machine, but it was fairly obvious that it would fail again.

The mode of failure is that the nichrome wire is getting too hot and melting through the Kapton tape, this is turn is making short circuits, and reducing the heater resistance, this is making more current flow, and the power to the heater is increased, I'm seeing a lot of max temp reached where the hotend starts to peak well in excess of the max temp permissible, (the max temp is to protect the peek)

But also the sudden rushes of current cause cause the power supply to stall, I've had steps being skipped, sometimes I've had axis appear to just re-home themselves, so instead of a single layer skipping, the entire model will just move two inches to the left have way through a print.

So this time I'm going to go all out and create a new hot end.

I'm going to base my design on the Jhead style heaters, with a block close to the nozzle, but instead of using a resistor I've decided to use a small ceramic heater.

Instead of tying my heater and barrel to the nozzle (which I may want to change to have greater or smaller nozzle widths) I'm going to stick with the M6 barrel of the solidoode, I'll stick with the removable nozzle, and I'll make a heater that can be screwed on and off just like the heatcore design could.

To start with I've located a 40w ceramic heater online that comes in a 23mm long 6mm diameter tubular package.

This will be my heater.

My block that will be used to store heat will be aluminium, (it's easy to acquire, relatively cheap -at least cheaper than brass)

The block will need to be at least 20mm wide to accommodate the 23mm heater, (it will not matter if 1mm sticks out either side -and this will help keep the wires away from the hot metal.
the block will be 10mm thick, this should mean that there is 2mm either side of the heater,
this will also allow for a 3mm hole to be drilled to install a grub screw to hold the heater cartridge in place.

The heater will be 2mm from it's opposite side of the block, and 2mm from the barrel of the machine, the barrel is 6mm wide, here will need to be at least 2mm on the opposite side of the heat block, (therefore the heater block must be 20mm x 10mm x 18mm, the most convenient size is 20mm x 20mm x 10mm)

Lastly the thermistor must also be installed in the printer, and must be thermally bonded reasonably well, to achieve this I plan to use heatsink style thermal compound and a second grub screw to ensure good contact.

Materials needed,
1 Aluminium block, (20mm x 18mm x 10mm) -I cut my block from a length of bar that was 20x10 x 2000mm
1 heater core, I bought mine as a 40w heater, but the measured resistance is actually 4.2Ohms, so it's actually a 34W heater.
3 grub screws I'm using M3 x 3mm
Thermistor -I'm re-using my original.
electrical connector - I'm re-using my original

Tools needed (at a minimum)
hacksaw -I'm using a B&Q value junior hacksaw -that cost 99p!
Drill
5.5mm Drill bit
2.5mm drill bit
6mm drill bit
M3 Tap
M6 Tap
Ruler
scribe for marking

so, here's the process.
First mark 18mm from the end of the bar

then cut off the aluminium block

now you need to use a scribe to mark where you want to drill

(the measurement that is missing here is that the M6 hole is centred 9mm from the far edge)

first drill the long hole through the block, start with a 3mm hole and then enlarge that to a 6mm hole

then drill a 2.5mm hole next to that, about 5mm into the block

now drill a 3mm hole and enlarge that to a 5.5mm hole (ready to be tapped for M6) in the face of the block

test fit the heater to make sure it fits

now using a 2.5mm drill bit drill three holes in the top face of the block.

unfortunately my drill bit broke inside the last hole, so I put a different hole in the side instead -the drill bit is still stuck in the block

now you need to use the M3 tap to create a thread on the two 2.5mm holes that are drilled through to the 6mm hole, and also in the final 2.5mm hole, (this should be on the top, but mine is on the side thanks to the broken drill bit)
Then you need to use an M6 tap to create a thread on the 5.5mm hole that goes through the block.
now we come to assembly.

the heater slides into the 6mm hole.
the thermistor slides into the 2.5mm hole.
the thermistor is secured with an M3 grub screw.

and the heater secured with two more grub screws

Now I've pulled the whole connector off the original green heat core wires, and attached it to the new red heater wires.

You need to remove the extruder from the machine, (the block catches on the carriage if you don't remove it to turn it)

then you can screw the new heater onto the machine and replace the nozzle.
after that the only thing left to do is re-mount the extruder, re-connect the wires and start printing!

The heat-up time is more or less exactly the same, and the stability of the heater is actually probably a bit better than the original heatcore, (looking at the graphs in RH)

Making a Lego Table

So this is a nice short post that details the Lego table that was made for my Daughters birthday.


It's a pretty simple idea, rather than having lego all over the floor, (not that this will stop that happening) a special lego table is created, where models can be created and worked on, perhaps over a number of days.

The basis for this table is a cupboard from Ikea that is a bit like those old school cupboards, there are some plastic trays that will be used to store the lego in.

On the top of the table base boards are glued to the top.

This table uses 32 x 32 piece boards, (three of them) and 16 x 32 stud boards, (4 of them) and a single 16 x 16 stud board

The total areas therefore is 48 studs wide (32 + 16) and 112 studs long (32 + 32 + 32 + 16)
there is an equal border, (about a 3 stud lego brick size) around the whole top

The boards were glue using solvent free evo stick (contact adhesive) glue. obviously a solvent based glue would melt the ABS plastic that is used to make Lego!

When the table is all put together it looks like this:

You can just about see the way that the boards are offset to try to minimise the lines.

Making a coat stand for a child

So I thought it was about time I finally wrote up the build of a coat stand that I made, (about 2 years ago).

The idea for this coat stand was sent to me by my friend who said I should make one for my daughter. I forget the exact link to the inspiration, but I do remember it was on Ana Whites website called "Knock off Wood, free woodworking plans for furniture http://ana-white.com/"

If you have a few days you should definitely check out that site, it's chock full of amazing furniture, includes plans.

You don't have to follow the plans, you can be like me and decide to make your own plans up in your head to build approximate versions of stuff on the site.

Anyway, now that I've covered where the idea came from it seems only right to give a little background.

Design
At the time I made this coat stand my daughter was about 3, she was getting to an age when you should care about your stuff, and start hanging up your coat etc, but not yet at an age where she could reach regular height coat hooks.

So the solution was obviously to build her a coat stand more suited for her.

This means that it should have pegs reachable by a 3 year old who stands about 3 feet tall, (so the height of the stand is about 4 feet, so she'd have to reach up at the start, but would not immediatly outgrown the stand.

I decided that the coat stand would need four pegs that would be at her current arm height that she could hand coats on, and a further 4 hat stand type pegs, to put hats on of course. As she grew the hat stand pegs would eventually become coat pegs.

So the parameters for design are:
four coat pegs, at about 3 feet from the ground, four hat pegs about 1 foot above the coat pegs, a stable base is a must.






Materials,
I decided that I'd use softwood to make this coat stand, it's easy to work with, and has a variety of finishing options from plain no finish, or varnish, to any colour as it's easy to paint.

The pegs I decided would be made of dowel. (12mm dowel so that they would not easily snap)

To build with nice proportions of 12mm diameter dowel pegs I decided that 48mm square pine was the best wood to use.



Onto the build
So the biggest gripe I had with the materials was the condition that it was in. I bought square planed timber from Wickes, this should be ready to go. if I'd bought rough sawn wood I'd agree that imperfections were ok.

So the first job was to inspect your materials and work out what I could do to cut out imperfections. like this:

Once I'd decided the best cuts for the wood (and there is no exact science for this that I'm aware of) I started cutting, setting the blade of my saw to 45 degrees I made a cut around 14 inches down the length of the wood.
then set the blade back to 90 degrees to make the next cut again about 14 inches down the length of wood.
This will gave me two bits of wood, with one square cut end, and the other end cut at 45 degrees.

Repeating the above gave me four of these. these will be the legs of the coat stand.

Next I made a 45 degree cut in the remaining (approximately 1 meter) length of wood.
Then flipped it over and made another 45 degree cut, then 2 more cuts and I had a square point.

I did this at the top and the bottom

Next I marked a ring about 1.5 inches from the bottom of the base of the point, this is where the legs will attach.

And a further ring about a half inch above that, (and another about an inch after that)

The centre of these lines are drilled with a 6mm drill bit, (ready to recieve a dowel peg to make a strong joint)

 Back to the legs.

Clearly the 45 degree cut is what will butt against the centre poll that I've been busy marking and drilling and making pointy.

But the legs do need some further work, and the moment the base will be the corner of the block of wood.

so I set my saw back to 45 degrees and cut an angle in the opposing direction to the mitre that will face the centre poll, then I cut again to smooth off the top of the leg.

I now marked and drilled the long mitred face of the leg, to recieve dowel pegs and glue.

Now I did a dry test of matching the joints (A dry test is where you put it all together without glue, this allows you to make any final adjustments before it's too late!!)

Finally I put dowel pegs and glue on the joint.
I set the first two joints against a table using wooden blocks screwed to the top to clamp it in position.
The final two legs were arranged with the blocks clamped to the centre stand, then the leg clamped to the blocks, (allowing the odd angled leg to be clamped to the stand)

Finally I drilled 12mm holes in the stand at about 4 feet from the floor. a hole going straight through, and another hole about an inch higher going through the other way.

Then I glued an 8 inch length of dowel into the holes, (with 3" sticking out of either side")

The hat pegs were drilled into the top of the stand, (about an inch and a half from the top, so the pegs are about as far along the centre poll as the legs are up it).

I don't have a drill press with a moveable table so I used a set square, and roughly lined the drill up to drill coat pegs at an angle into the top of the stand.

Lengths of 12mm dowel we then glued into these holes.

Finally the coat stand was painted a pastle pink colour.

Glass bed upgrade for Solidoodle

So I'm beinging to find that I'm habing some issues with my solidoodle, the issues are that the aluminium plate that acts as the bed is warped.

I've attached a dial gauge to the print head, and measured the warping.

You can see the red areas, are more than a full layer higher than the top corner.

This means thatI have intermittent issues with the first layers sticking to the beds, in some areas of the bed the bed is too close to the extruder and a short fat line of filament is squashed onto the bed.

In other areas the extrusion comes out of the extruder and is almost gently placed on the bed, keeping it's round shape and not sticking very well at all!

The flattest thing that I have is some glass. - and I wonder if it's possible to texture the glass so that there is no need for Kapton tape on the bed.

I do not have the facilities to etch glass with sand blasting, - whih would create a lot of texture, so I will try experiments using a chemical etching using hydroflouric acid.

This puts a nice grey sheen onto the glass, and I've stuck the glass to the printer using some tape.

Unfortunately, the bed texture does not help with ABS sticking to the bed. 

But, Kapton tape still sticks, so using this in the print area on top of glass is certainly no worse than what I had...

Now, I have that first issue with the warping, and even with a glass sheet on the bed, have a seoncd issue. I'm finding that the heat distribution of a central power resistor just screwed to the bottom of the bed is meaning that the centre of the bed is very hot, (and causes the first few layers to melt and deform, whilst the outside edges are not at all hot, so the extruded plastic has trouble sticking.

As a proof of concept, I've added a second glass sheet and Nichrome wire wrapped around this to create a heater that spreads the complete print area.

And good news, I can print on this bed once covered in Kapton - no glass etch needed.

Couple of issues with this...
Many people have started putting a sheet of glass on top of their aluminum beds and holding it with binder clips to ensure that it doesn't move.

but, whilst the glass is level, this integrated heated may, or may not be level. - it covered the bed leveling screws so it's not possible to level the bed with the glass on top, and not possible to get the bed level without having the glass on top...

I've decided that I'm going to replace the warped bed completely, and try to get more even heating by using some nichrome wire to heat the bed all over. - a gomplete glass bed.

You can get heat proof glass from a glass merchant, sounds silly, but look for one that specialises in glass for home made wood burning stoves.
As a guide to price, I got a piece 7" x 7" 1/4" thick £13 (GBP) that was the price to get this measures and cut
The rest of this post is my new glass bed.
To start remove the glass that you've either clipped or taped to the aluminium bed, (for those wanting to avoid the hot end bumping into binder clips, use 1/4" kapton to stick down the glass:

remove the kapton, (you need to get to the screws:

Using a "china marker" go ask someone working on a deli counter to get you one, mark the edges of where the glass can comfortably sit:

You won't need to do this if you're using a 6x6 piece of glass, but of you want to use all the extents of travel of the hotend, then you'll need to make sure that the steppers are cleared

next unscrew the aluminium. remove the heat shield/insulation from the back.

now remove the resistor and thermistor:

now the bed is completely removed

Next using the marks on the glass put the bed under the glass and mark the screw holes.
using a glass bit drill the glass, (either 4mm or 5mm) and countersink the holes.

now take three 9ohm lengths of nichrome wire, and a 1/4" roll of kapton, loop the wire over the underside of the bed using the 1/4" kapton to hold it to the glass

Join the ends together to make a 3ohm resistor evenly spread over the whole bed,
tape the thermistor to the bed in a spot where it's an even distance from any length of nichrome.
join the red wires where the resistor was attached to the ends of the nichrome
and replace the heat shield
Level the bed...
next, because glass isnt all that sticky, you'll need kapton

a nice big roll will do!
lay the kapton over the bed, stick one side first, use a plastic squeegee (you can print this!) to push the kapton onto the bed without airbubbles.

Done

Printing on an all glass bed.

The bed takes the same time to heat up, but rather than getting a middle of spot of around 90 degrees with cooler edges, (so the middle of a print squidges and the edges lift, I can print with a bed temperature of around 70Degrees (and have confirmed the machine readings with a thermocouple probe)

I've also increased the area that I can print on by almost a full inch in the x and y planes.