Over the past few months I have been playing with 3D fractals to create slip cast pottery.  I found a free program called Mandelbulber 3D and you know me, If it’s free I’ll take 3.  It’s shocking to me the availability of free software like this.  Right now I am just scraping the surface on what the software can do but I have a few examples of shapes made in the software posted on Thingiverse.

https://www.thingiverse.com/thing:5138435

Creating the fractals with the Mandelbulber is fairly straight forward.  Just experiment with varying a few values and click render.  The hard part is getting the shape to be cast-able with out having to make a 27 part mold.  A few weeks ago I pulled the first cast from my first successful mold.  This is part fractal and part Fusion.  The foot of the cup is part of the fractal pattern and the body of the cup is a shape designed in Fusion 360.  Although the final product warped in the kiln I think it was a good proof of concept.

After the shape is created digitally you have to make it physical.  My go to method is usually my 3D printer.  The constraints that make a part easy to 3d print without supports are similar to the  constraints that make a part easy to remove from a mold.  To make the slip cast mold I don’t print the cup but a plastic mold of the cup, there are two reasons for this.  First if you are going to make lots of slip casts you are going to need more than one mold.  Because of the time it takes to cast each cup you will need to pour several mold each day.  Second with a hard plastic mold you can make a soft silicone part.  This saves me from making a large silicone Mother Mold of my 3D printed mold.  My Mother Mold is half of the 3D printed mold with the full silicone cast part inside.  It’s worth noting that there is 15-18 percent of shrinkage from pour to final firing so you will need to scale up your prints to an almost comical size. 

(photo coming soon)…

On a side note I did some experimenting is soaking silicone parts in IPA to expand them.  This is a fun exercise if you have never done it.  To expand a part just place it in a container of IPA for several hours.  I let one part sit over night and go about the amount of growth I was looking for to but the part shrinks down slowly when removed from the IPA and the growth amount is not very predictable.  Below you can see an example of how much larger the part grew and the final fired piece from this process.

I am in the process of printing my molds right now so tonight at the open meeting I might have printed molds to show.  I also have other shapes to pass around.

If I include the Pi in the traveling mascot, I’m convinced it will not survive the inevitable rough treatment. The only other use I can think of for a Raspberry Pi in a travelling mascot is as a home base server for the mascot, publishing the travelogues. Yet it’s too unstable for even that task.

I still like the idea of a traveling mascot that can track it’s own travels, but I’m convinced that building it around a Raspberry Pi is not the proper foundation. I really like the little GPS unit that came in this kit, and will try to build a scaled down version of the traveling mascot with a USB interface to hook up with any computer for collecting data.

Thanks again Adafruit Industries, we really appreciate the kit, and we’ll continue to work with the parts on other projects. Like vultures, some other members have already picked off some pieces of the kit for their projects.

Previously on The Raspberry Pi Challenge…

Just a quick update on the “Milwaukee Makerspace Traveling Mascot” project as I caught Eric doing a bit of Raspberry Pi + GPS hacking last night.

I’m excited to see how this project progresses. I’ve not had a chance to get hands-on with the Adafruit Ultimate GPS Breakout yet, but there’s a great tutorial on using it with a Raspberry Pi and one that covers Arduino usage as well.

Thanks to our friends at Adafruit Industries, we’ve got an awesome Raspberry Pi Starter Pack (and a few other goodies) and we decided that rather than fight over who gets to play with it, we’d issue a challenge to our members: Tell us what you’d build with the kit.

The results are in, and we’ve got a bunch of entries to look at before we decided who will be chosen take on the challenge. Hopefully in the next week or so we can reveal what the winning entry is.

But don’t worry, we’re going to share a bunch of the ideas right here on the blog. We may not get to build them all, but we’ll do our best to highlight some of the ideas that our members have come up with.

(If you’re looking to get into using the Raspberry Pi in your projects, you’d do well to check out the Adafruit Learning System’s category on the topic.)

I have been a member here at the Milwaukee Makerspace for about 15 months now.  One of my favorite things to do here is machine architectural reliefs from foam.  I studied architectural history extensively at UWM, so I have a lot of influences to draw from.

The first piece I did was 3/8″ deep, since that’s the bit we had at MMS.  I first tried a piece with all flat surfaces.  It turned out very well, so I tried another piece that has slanted roof surfaces; again, success, so then I did some searching and found a 1/2″ deep milling bit.  I did several pieces “on a theme”, taking the first one and making slight modifications. All of these designs are my own creations, I just daydream and think them up.

I have found that I can get 1/64″ details on these pieces.  I have recently started using 1″ deep bits, and the results are fantastic!  The best part is that the foam is really cheep-cheep-cheep, $25 for a big sheet at Home Depot!

My process is:

1) design in Solidworks (CAD)

2) Export to .STL file format

3) Import into Cut3D, where I generate G-Code

4) Load into Mach 3, the software that controls the CNC router.

5) Let the foam fly!

I started out on the MMS router, which uses leadscrews; my newer Zenbot machine uses belts, and is blazing fast.  I can now machine 8 times faster!  The largest piece shown here went from about 19 hours down to 2.5 hours.

My next challenge is to get small lines onto my pieces that will represent bricks/mortar, etc.  I’ll have to generate different code for that; the milling code runs in 3d, but the “bricklines” will need to be in 2d, so I’m looking forward to that challenge.  I’ll be using Vectric’s “Aspire” software for that.  More to come!

-MattN

I was inspired by the open source work of Pete at RasterWeb! and his recent effort to bring “The Button” to a wider audience of busy or non-makers.  He has freely helped tens of people create their own buttons, but is now able to fulfill requests for preassembled units. Among other applications, these USB buttons can be used as the shutter control of  Mac powered Photo booths at public events. These photo booths are powered by Sparkbooth, which can automatically upload the photos to Facebook, Twitter, tumblr or other social media sites.  His buttons emulate a keyboard, and contain an Arduino Teensy (only 0.7″ by 1.2″), which is a USB based AVR microcontroller.  Despite the Teensy cost of $16, I saw an opportunity for cost savings by opening a standard USB keyboard and spending a few minutes to extract and reverse engineer their compact circuit board.  Although this isn’t a solution suitable for even small scale production, it can work for a one-off prototype, like The Critic.

Below are several photos that show the process of opening the keyboard to extract and modify the circuit board.  When the top of the keyboard is removed, a sheet of silicone ‘popples’ is revealed.  These ‘popples’ are the springs under each of the keys.  Under this layer are two sheets of thin plastic, one with conductive ink traces that are (mostly) horizontal, and one with conductive ink traces that are (mostly) vertical.  These layers of traces are separated by a small gap.  When a key is pressed, a protrusion on the bottom of that key’s popple pushes the two layers of plastic together at this location: connecting one of the vertical traces to one of the horizontal traces. These traces are routed to the circuit board via a row of contacts under the front edge:

The chip (under the black epoxy potting on the bottom of the board) detects this electrical connection, and outputs the appropriate character over the USB cable.  The keyboard, popples and plastic layers can all be replaced by an external switch and wires soldered directly to the circuit board.  The photo below shows wires (whose free end is to be connected to the switch) soldered to the pads required to output a space bar character.  To output other characters, simply follow the vertical and horizontal traces to the board, and solder wires to those pads instead.

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Back in August, Tom acquired several Smartboard-brand projectors and was interested in getting them to work as a normal projector would.  As you may recall from my original post on this project, these projectors will not display anything other than an error screen without their accompanying interactive whiteboards connected.

The original approach was to simply substitute my own video signal by swapping out some cables.  There is a dual-link DVI cable that attaches to the projector lamp assembly through the telescoping neck of the projector to its wall-mounted computer base, the Unifi 35.  I tried simply connecting a computer to the DVI connection on the lamp, but the lamp wouldn’t power on.  We eventually surmised that the lamp and the Unifi 35 were communicating somehow through the DVI cable and the lamp wouldn’t power on unless the computer detected that it was attached. Computers with DVI connections have the ability to detect when display devices are connected as well as instruct them to power on or off.

That led to trying to swap out individual pins in the cables.  I built three DVI breakout boards and set up a breadboard so I could mix and match pins from two sources and combine them to send on to the projector lamp.  I tried using the digital pins from my own source (a G5 Macintosh) and the analog pins from the Unifi 35.  After a lot of trial and error, it seemed the projector was communicating with the Unifi 35 somehow using either the analog pins on the DVI connection, the second digital link, or both.  Also, it seemed I could disconnect some pins after the projector was powered up, but I couldn’t start without them.  It looked something like this (table copied from Wikipedia):

After a lot of trial and error, I didn’t seem to be much closer to the goal of getting my own video source to display.  I also began to consider that the manufacturer may have switched around some pins between the Unifi 35 and the projector to prevent consumers from servicing the unit.  The DVI cable I was working with was internal to the machine after all.  There’s no reason any one would ever try to connect their computer’s DVI output to the lamp itself.  Signals leaving the Unifi 35 could be sent on a different pin than the DVI standard suggests and then rearranged back into the standard configuration at the lamp assembly.  I never really dismissed that possibility, but I also didn’t see much to support it.

I trudged on and hooked up an oscilloscope to monitor was was going on with the analog pins, C1 through C5, because they seemed to be critical to the lamp turning on, but not necessarily staying on. This is what I found:

Pin	Description	In Standby Mode	Once Powered On
C1	Analog red	0v constant	+3.3v constant:
C2	Analog green	+5v constant	+5v constant for 0.93 seconds every second then a brief flash for 0.07 seconds of this waveform: +5v (58% of the time) 0v (42% of the time) at ~1.2 kHz
C3	Analog blue	+5v constant	+5v constant for 0.93 seconds every second then a brief flash for 0.07 seconds of this waveform: ~0v and a more complex pattern (0.8 ms/3.5 ms) +5v (0.8 ms/3.5 ms) ~0v and a more complex pattern (1.1 ms/3.5 ms) +5v (0.8 ms/3.5 ms) at ~285 Hz
C4	Analog horizontal sync	0v constant	0v constant for 0.93 seconds every second then a brief flash for 0.07 seconds of this waveform:
C5	Analog ground	Reference for all	Reference for all

Unsure of what these signals represented, I consulted with Royce, Tom, and a few others and worked up the courage to use a logic analyzer for the first time.  Most of the work was wiring the thing up and assigning names to the leads in the software.  My breakout boards turned out to be more fragile than I expected so I ended up resoldering a all of the flaky connections.  The Intronix 34-channel Logicport Analyzer is pretty slick and comes with some great software tutorials.  Once I got it going, it was fairly straight forward.  I can definitely see how this device can come in handy now that I’ve used it.

One of the first problems I ran into was the multitude of different voltages at work.  The Logicport software has a logic voltage threshold setting to help weed out logic from other signals, but I found myself dealing with signals less than 0v, as well as +3.3v, and +5.0v.  I eventually scanned the spectrum and sat, clicking the threshold up in small intervals of 0.05v, and watched to see if anything appeared on the screen.  It would seem that while in standby mode, some of the the TMDS data pins and the DDC clock and data pins are held above +2.0v.  Around 0.0v, some of the data shields show some variation between low and high during standby but as the projector is starting up, there are definite patterns on TMDS data shields 2/4, 0/5, and the clock shield.  TMDS link 1 shows some activity during startup in the +3.3v range and then shortly after link 2 does as well as the analog red pin.  Why a digital signal might appear on the analog pin is unclear.  I could be measuring it wrong also, but there does appear to be a signal there.  I also checked the analog pins during standby against what I saw with the oscilloscope and the numbers seem to agree except that the C4 horizontal analog sync pin showed voltage at or above +2.00v with the analyzer when the oscilloscope showed no voltage difference at all.

Since I was more interested in the control data than the video data, I focused my attention to the DDC clock and data pins to see if I could decipher how the projector and Unifi 35 were talking to each other.  PC monitors and projectors with DVI connections use a display data channel (DDC) and a standard called I2C (I squared C).  I found some great information on I2C and DDC protocols online here and here.  At +5.00v I read a portion of the communication between the Unifi 35 and the projector and tried to analyze it.  Unfortunately, the data doesn’t seem to follow what I’ve read on the I2C standard. The clock rises and falls unexpectedly, the start/stop commands don’t appear where I would expect them to, nothing resembles a 7-bit device address and there is seemingly no pattern to data.  The other logic analyzer screenshots can be found here.

We considered trying to spoof the USB connection to the whiteboard at one point, but that seemed to be problematic also.  I set up the logic analyzer and monitored the USB connection, but to no avail.  It’s possible that without the board to receive power from the USB port, there’s no way of telling how the board would communicate with the Unifi 35 and projector.  In a last ditch effort some weeks ago, I contacted Smart Technologies, makers of these products, and flat out asked them if the projectors could be used without the whiteboards.  The answer was, unfortunately, no.

I began to lose interest after this and once I got back to the project after the holidays, I decided to finally give up on it.  I would rather use my time on other projects.  It was by no means a waste as I gained more experience etching my own circuit boards, soldering annoying small connections, and I got comfortable with the logic analyzer; assuming I used it right.  I also became wary of computer cable vendors on Amazon.com.  During the project I needed some dual-link DVI cables, but when my order showed up, the second data link pins (the six in the middle of the connector) weren’t even wired.  I stuck a multimeter to them and found continuity on all but those six pins.  Needless to say, I left them some grumpy feedback and got a refund.  Thanks to everyone who helped and gave me advice.  As Shane said, “I doubt anyone else would have gone this far.”  I took that as a compliment.

Today marked the first monthly meeting of The DIY CNC Club at Milwaukee Makerspace.  Ron Bean and Tom Gondek, the creators of the router, guided members and guests through the use of CamBam CAD software to generate G-code and Mach3 software to operate and control the router.  The day before, Tom and Mike tested the machine’s ability to cut aluminum.  On Sunday, Rich created a decorative wooden sign and Brant began making plastic shapes for a project enclosure. As Ron pointed out, in less than 24 hours we had worked in three different materials: wood, metal, and plastic.

Several items were also crossed off our wish list.  Two emergency stop buttons were added to the front of the machine and wired together in series.  Hitting either one stops all motion in the X, Y, and Z planes and pauses the program.  We also built a relay-controlled receptacle box that when wired into the CNC computer, will be able to stop the spindle so hitting the E-stop will kill all motion in all axes and the router.  For some reason the pins we’re using on the parallel port are only producing 1.6 volts instead of the 3 or 5 we expected and the relays won’t turn on.  All in all, a very productive weekend.

If you haven’t noticed, I’ve been spending a lot of time with the MakerBot at the space lately. (And yes, it’s now much quieter and doesn’t force you to yell in the lab when it’s running.)

Last night Dustin stopped by to work on calibrating it a bit more. (He maintains one of the MakerBot Thing-O-Matics at Discovery World.)

We made a bit of progress by tweaking things in Skeinforge, and after much calibration test printing I thought we should print one “fun” thing before the night ended.

We chose the 1:9 scale model Apple II+ from Thingiverse. It seemed a fitting tribute to Steve Jobs.

A time lapse video complied from the Milwaukee Makerspace CCTV system. 7 hours of video compressed into 4 minutes. All events took place between 4:30 and 11:30 PM Thursday, September 29, 2011.

Activities include:
– Rich welding
– Chris and Rich working on their electric cars
– Chris driving his electric car in and out of the shop
– Tom, Adam, and Royce working in Diptrace
– Bret, Rich, Royce, and Adam blacksmithing items with the forge
– Various people working on misc. projects and chatting
– Royce, Brant, and Adam etching and tin-plating circuit boards
– Pete working on his Makerbot 3D printer