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Capacitive Distance Sensing with the MPR121 and Arduino

The MPR121 is a small little chip that can be used for creating touch sensors that can easily integrated into your Arduino projects as this article nicely explains:

http://bildr.org/2011/05/mpr121_arduino/

But the MPR121 can do more! You not only can read touch / no touch binary values, but also read the measured capacity, which is a measure for the distance of your hand:

To do that you need to read 2 consecutive bytes over I2C. I added a method to do that. Also you need to adjust the initialization code and play with some values to adjust to the size of your sensor (mine is just a piece of aluminium foil).

The connection to the MPR121 is exactly the same as described in the bildr article, but you can leave out the IRQ line (we want continuous reading of the values).

You can find the source code for the shown demo here.

New Lamp for the Living Room

Finally finished the lamp for my living room. It consists of 45 identical paper pieces (white on the outside, golden on the inside) which I cut with a laser cutter at the FabLab Munich.

See the full gallery on Posterous

The photos show the lamp with the light turned on and off.

#JustMigrate

Programming the ATtiny2313 with the Arduino IDE

The guys at High-Low Tech found a neat way to use the Arduino programming environment with small AVR microcontrollers, namely the ATtiny44/5 and 84/5. This is a great alternative to a full Arduino board for simple projects, because they are cheap and small.

I wondered if the approach could also be used for the slightly larger/more powerful ATtiny2313. And as it turns out it is not only possible, it also has been done already. Oh wonders of the Internets!

Florian Schäfer has made the effort and it works wonderfully. Just follow the instructions from the High-Low Tech page but use these files (here in a zip) instead of the original ones.

The pin mapping of the ATtiny2313 looks like this:

#JustMigrate

Laser-Cut "Frabjous"

"Frabjous" is a scupture by Georg Hart. It's made of 30 identical S-shaped pieces. Some time ago I did a paper version of it, but always wanted to do a laser cut wooden one.

Finally I got around doing it. Contrary to the original, my pieces are self-interlocking, so no glue is needed.

See the full gallery on Posterous

You can get the design files here on thingiverse.

#JustMigrate #fablab #FabLabMuc #laser

Create 3D models from photos: A quick test of Autodesk Labs' Photofly

Project Photofly is a program and a web service, which lets you convert a series of photos of an object into a 3D mesh.

I gave it a quick test.

I made around 50 photos of a small double headed figure (around 20 cm high) and used the tool to create a 3D mesh from it.

This is the result:

Here is one of the photos:

I'm really surprised how easy it was. After reviewing the photos (and rejecting a couple of them becouse they were too dark) I just imported them into the Autodesk tool. The photos get uploaded into the cloud and after a short while the result can be downloaded. And the result was great! I didn't do any manual editing in Photofly whatsoever, the photo/camera positions where all calculated correctly. After exporting the mesh (it contains textures too, but for 3D printing I'm not interested in them) I loaded it into netfabb Studio. The mesh was pretty much complete, only one bigger hole under the chin where I didn't provide enough info with the photos it seems. Besides that there were only smaller holes, all of which could be automatically fixed by netfabb. I just had to cut off the base and now I have a great watertight 3D model.

Really promising, given that was my very first try.

Here's a video showing how you should take the photos:

#JustMigrate #3d #rrbb #scanner

Stencil Painting with the Help of a Laser Cutter

A small experiment to use stencils created with a laser cutter to create a painting with acrylics.

First I took a photograph and fiddled around with the color curves:

Then I ran some filters (median etc) to get rid of noisy areas. After that I created 2 layers (one for each the darker blue tones). More filtering and some manual painting made sure the stencils can be made out of them (all parts of the stencils need to be connected with no "islands" left).

The 2 layers look like this:

Then I loaded the frames into Inkscape, where I traced them to have vector outlines, which are needed for the laser cutter:

As you can see, I also added registration marks to the top corners, so that I could align the stencils correctly.

The cut stencils look like this:

I taped the stencil on a canvas and applied the first color using a small foam roller. After drying I did the same with the second stencil/color

After some manual finishing touched (e.g. white dots in the eyes) the result is this:

#JustMigrate #cutter #laser #painting #stencil

Look what I have found in the Ars Electronica Center: my ellipical gears!

Visited the Ars Electronica Center in Linz today. And what do I see in their FabLab? My ellipical gears!

They found it on thingiverse and printed it on their 3D printer.

#JustMigrate #3d

Printed a Penrose Triangle. Optical illusion + 3D printed = double awesomeness!

Printed the fantastic Penrose Triangle Illusion by chylld The illusion works even better on video:

http://www.thingiverse.com/thing:6513

#JustMigrate #3d #rapman #rrbb

First results from our CNC mill

Over at the FabLab Munich we are currently building our own CNC mill. Almost finished now.

Here is one of the first pieces done with it:

The mill is not perfect yet, but we are getting somewhere!

#JustMigrate #CNC #FabLabMuc

Modified Z Switch for the RapMan

I have upgraded my RapMan with a heated print-bed and needed a modified z switch holder (the z switch normally is mounted directly on the print bed, which is not a good idea if it is heated). I tried Laszlo’s one, it works, but I had problems with it. It is attached to one of the 3 screws the print bed is hold by. These 3 screws are equipped with a spring mechanism, allowing the print bed to back down if the print head by error tries to go down below the print bed surface. When attaching Laszlo’s z switch holder, this spring has no effect any more. Laszlo says he doesn’t have the problem and I think the reason is that I have a RapMan version 3.1 while he has a previous version. My RapMan z stage platform has threaded holes for the 3 screws I was talking about which seem to be the reason for problem.

Anyway, I designed a different solution, where the z switch is not attached to the print-bed but to the z stage platform instead. This also makes fine-tuning the print-bed/extruder distance easier. You can do that with the 3 screws now and you get direct feedback about the new distance. Before you had to turn the distance screw at the print head and run a home sequence to get the new adjusted distance.

With this new mechanism the z switch is not pressed directly, but there is a arm which presses it. The arm reaches up where the distance regulation screw comes down during the home sequence.

Here you see my RapMan with the heated print-bed and the new z switch mechanism in the left back corner:

Here a couple of close-up photos. In case you wonder, I added a bit of duct tape because I needed a M3 screw to hold the arm and the only one I had left was a bit too short, so the duct tape holds it in place :-)

See the full gallery on Posterous

The OpenSCAD and STL files for the 2 printed parts can be found on thingiverse.

#JustMigrate #rapman #rrbb #rrbb2

My new heated print-bed

It is already a couple of weeks since my heated print-bed from László arrived. I was busy so I didn't find time yet to update the blog, but finally here is my experience with building and installing it.

The print-bed is made of aluminium. It's heated from the bottom side using power resistors. The print is done on a Kapton-covered steel sheet which lies on to the of the aluminium bed and which is hold in place by powerful magents.

The bottom side has threads to attach 9 power resistors and pits where the magnets will find it place. First I covered it with Kapton tape, cut out holes for the resistors (I only used 5 in the beginning) and the magnets:

Then I added the magnets. U/D stands for up/down for the orientation of the magnets.

László recommends to add iron bars on top of the magnets. This makes the magnetic force stronger. Neodym magents don't stand heat that well, but short-cutting them with the iron bars also seems to improve this. I decided to mount all 9 resistors I ordered at that point, so I added the remaining ones too:

Then I wired the resistors. For a start I was only using 6 of them, this is why the middle 3 are not conencted. Here the 3 mounting screws an the z-switch holder are already added as well.

I tested the bed in this configuration, but it was not getting hot enough. Even with all 9 resistors it hardly reached the temperature where ABS sticks to the steel sheet, which should be at about 100-110°C.

So the next step was to add heat insulation. To prepare that I added the heat-resistant insulation for the connecting wires. I chose not to wire all the resistors together but have two groups with 6 and 3 resistors to have more possibilities later.

Then I covered the bottom side with the rock wool. I also attached a thermistor to the bottom side of the bed, so there are now 5 wires coming out there. Shouldn't have done this in our living room really, it's quite a mess. I'm lucky I have an understanding wife.

OK, now the bed was ready to be installed. Removed old bed, replaced it with the new one, attached the power transformer, covered the steel sheet with Kapton. I wasn't happy with the z-switch holder, so I replaced it with a newly designed one (more in an extra post later).

See the full gallery on Posterous

Turned out that the temperature now was ideal for printing ABS. I now always switch the print-bed on about 5 minutes before the print and leave it on for the whole print. With all 9 resistors connected (all parallel) the power transformer which comes with the kit is a bit too weak by specification. It gets a bit hot, but it works fine. I'll probably add a fan for it later. I didn't measure the temperature, but the ABS sticks very well on the Kapton. I didn't have to do anything (like sanding) to improve the adhesion.

See the full gallery on Posterous

Here's a finshed print (lots of strings, but that's not the fault of the print bed). I'm using the scraper which came with my RapMan to remove the steel sheet (it's not that easy, the magnets are really strong). I added small pieces of card-board on both sides of the scraper so that I do not burn my fingers. When the print is cooled down a bit you can remove it from the sheet.

Right now am really happy with the print bed. Its a bit costly, but it is nicely made and very flat. And it probably cannot be made cheaper really. You would have to go for a different approach like a circuit board, but I haven't seen one which covers the full RapMan print area.

I do not sand the Kapton, so the bottom faces of my prints are really nice, flat and shiny. I did not have any warping issues any more when using it. I didn't print really big objects yet, this is one of the next things I will test, but I do not expect problems.

#JustMigrate #heated #printbed #rapman #reprap #rrbb

My heated print bed kit arrived

I ordered a heated print bed for my RapMan from László which arrived today. Here are some unboxing pics. Looks promising!

See the full gallery on Posterous

#JustMigrate #rapman #reprap #reprapbuilding #rrbb

Now experienced that evil head dive bug too. The "naked lady" doesn't look too good... #rapman #3dprinting

Time to upgrade my RepMan firmware. Version 3.0.0 should be out soon.

#JustMigrate #3d #rapman #rrbb

The 10$ Heated Printbed

I had a couple of objects where I wanted a really flat, clean bottom side, which is hard to archive when printing on a raft with your RepRap/RepMan. So I wanted to have one of these heated printbeds where you do not need a raft - the objects stick to it directly and due to the heat they do not shrink while printing avoiding the warping problem ABS has which would cause the edges to come off the printing surface otherwise.

But I did not like spending lots of money in a machined metal table. I'll probably will get one now, but for trying it out and playing around I looked for something cheaper.

So here is my (roughly) 10$ heated printbed design. You need:

flat piece of wood board

a proto-board with stripes (something like this)

Kapton tape

old PC power supply

I soldered bridges onto the protoboard so that the whole board is covered by one long zig-zag ciruit. With my board size of 160x100mm (Euro card size) this resulted in about 2.5 Ohms. Attaching that to 5V resulted in about 60°C which is is not enough, but with 12V it was at about 90°C, which proved to be enough.

I covered the board with Kapton so that the holes are covered and ABS sticks much better to it. I mounted the proto-board on the wooden board using little wooden pieces as spacers which I covered with a few layers of Kaption tape for insulation. I wrapped some Kapton all around the proto-board and the wooden board which proved to be enough to hold it in place. I glued the wooden board onto the print bed mount of the RepMan using double-sided take. Pay attention to what take you use, mine was really hard to get off again.

See the full gallery on Posterous

In case you wonder, my proto-board was broken, so I soldered it together again. Made a bit of trouble, because it was not flat any more.

So does this work? Yes, I was able to print a couple of nice objects with it. However, there are a couple of cons:

The prints stick really well. This is good, but you have to wait for the printbed to cool down before attempting to get the print off, otherwise the object will get bent. Once I was ripping the proto-board off the wooden board while trying to get the print off. Also the Kapton tape came off easily.

I had problems to get the printbed flat. Mostly because of the broken proto-board so that probably a problem that could be avoided easily.

100x160mm is enough for many objects, but if you have a RepMan you could do much larger prints. When using larger proto-boards the resistance will be different, so you need either a higher voltage or you need a different way to connect the stripes on the board. Either way you probably need a higher rated power supply.

The proto-board started smelling funny. I think it was a really cheap one (don't know, I used one I had lying around) so this could be avoided by using a better, more heat-resistant one.

It was a fun experiment and useful for smaller prints. But I guess I get something better now.

#JustMigrate #3d #heated #printbed #reprap #reprapbuilding #rrbb

Modeled the FIFA World Cup Trophy for my 3d printer. Just need some gold paint now...

For the Germany-Spain game tonight I printed this. I just need some gold paint now... You can download the STL file at http://www.thingiverse.com/thing:3494

See the full gallery on Posterous

Update: after painting it with gold spray paint and adding the dark green stripes, it looks like this:

#JustMigrate #3d #reprap #rrbb

Finally a successful print of my Tie Interceptor #reprap #3dprinting #starwars

Print quality still could be better, I had lots of "strings" to remove. While doing this, one wing broke off (I glued it back on). The thing was printed in 2 parts. Gluing them together did not work as well as I hoped as the pieces had quite some warping. Maybe it would print better in PLA instead of ABS. But hey, the kids like it! :-)

#JustMigrate #3d #reprap #rrbb

Cool! @bre likes my Star Wars Tie Interceptor on Thingiverse!

http://www.thingiverse.com/bre http://www.thingiverse.com/thing:3006

#JustMigrate

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