Chocolate Printer Cooling System Test

This week I attempted the first test of the chocolate printer cooling system.  The cooling system is intended to solidify the chocolate just after it leaves the extruder nozzle so that by the time the next layer is started it will have a solid layer to sit on.  The cooling system consists of a centrifugal blower with a brushless DC motor blowing room air into a styrofoam cooler containing a block of dry ice.  The air passes over the dry ice and gets chilled as the dry ice sublimates directly into very cold CO2 gas.  The chilled air and CO2 mixture exit the box through a port with a hose that will ultimately blow the cold air on the chocolate.  At least, that’s how it is supposed to work.  It blows air at -12C as measured via a thermocouple, but unfortunately, the air exit port ices up in about 2 minutes and blocks the air flow.

There are many possible solutions.  I can add a heater to the exit port to prevent formation of ice, or dry the air going into the box using a dessicant cannister or maybe just use water ice instead of dry ice if the higher temperature will still cool the chocolate adequately.   Maybe using an old miniature freezer with an air hose coiled inside would do the job.  It would be really interesting if I could use the waste heat from a freezer to keep the chocolate liquified and flowing.  Back to the drawing board!


Recently Arduino came out with the Arduino Zero. This is a neat 48MHz ARM Cortex M0 processor on a PCB with the same pin outs as an Arduino UNO. Existing 3rd party UNO libraries are a little hit and miss because some access the underlying hardware registers of the UNO. The Zero hardware registers are completely different from UNO. Still, the basic 1st party Arduino libraries work fine and I’m sure those 3rd party libraries that were twiddling the UNO hardware registers directly will start to support the Zero over time.

Anway, my curiosity was peaked by the ARM processor for the Zero the Atmel ATSAMD21G18. It turns out that the processor has alternative packages with higher pin counts. Same silicon, just more pins. So I gave the ATSAMD21J18 a try. In order to be able to use extra pins with digitalWrite, I had to add a small amount of code to a file called variant.cpp, but once done, I had a Zero with a nice chunk of extra I/O capability.

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Custom Police Badge

I was a “Grammar Police” officer for Halloween this year.  My costume consisted of some standard police equipment, as well as a dictionary, thesaurus, citation tablet, red pens, and, of course, my lovely custom badge!


Step 1: Design.

I scoured the web for pictures of “grammar police” shields, but ended up creating this design in Microsoft Word, using clip art from the web, generic shapes from Word, and shaped text boxes.  It was pretty simple and used the software I had readily available.  The portions of the design that are solid black are the parts that will be etched into relief during the process.


Step 2: Create!

With much encouragement & assistance from a fellow Makerspace member, Jon (of Dalek Asylum fame), I crafted this badge using mostly jewelry-making tools & methods.  We first spray-painted a square piece of copper, then used the laser printer to burn away the paint from the sections that were solid black.  This gave us access to the “fields” that would be eaten away in the etching process, giving the piece segments of relief.

After some clean-up (note to self: don’t use abrasive cleaners at this step next time!  and maybe not industrial spray paint, either), we left the copper square to soak in ferric chloride for approximately 45 minutes.  We checked the progress of the etching every 15-20 minutes, and decided that after 45 minutes we had enough of an etch to give the details enough depth to stand out.

After more clean-up to remove the ferric chloride & remaining paint, I had a nice, shiny, scratchy piece of copper with an etched design.  At this point, I really started finding my way around the jewelry bench.  I used a small jewelry saw to cut along the outer lines of the badge, which was frustrating until I found the right rhythm for cutting.  My badge was finally starting to take shape!

From here, I filed the edges smooth & buffed the finish to remove some of those fine scratches.  I gave the piece some dimension by using tools at the jewelry bench to accentuate the “belly” at the bottom of the shield.  Once it felt reasonably even and I was happy with the general appearance, we applied a liver of sulfur gel to the surface of the badge.

The liver of sulfur settled nicely into the etched corners, giving the piece an aged patina and highlighting the small details.  I really like how it settled into the fine lines left by the etching solution around the perimeter of the main field!  The small striations in the copper there give it a very unique appearance.  The patina provided by the liver of sulfur also helped hide some of those fine scratches I mentioned earlier.  We wiped off the excess & applied a museum-quality wax, since the badge will be worn and handled like jewelry, to maintain the patina.

Step 3: Profit(?)

The badge was added to my collection of Grammar Police equipment, which included shiny aviator sunglasses, and a tactical belt (excess nylon webbing with a clasp) with a dictionary, thesaurus, red pens, custom grammar citation padlet, and toy handcuffs.  It was quite the fun costume, and even though none of my trick-or-treat’ers understood, all my friends did!


Thus ends the story of my first Makerspace project.  Oh, what fun it was!

Time Delay Relay

Time Delay Relay

I’m working on a project that requires two power strips to be turned on in a sequence. The first power strip powers 6 HDMI displays, and the second one powers 6 computers. The displays have to be on before the computers so they sync properly and get the correct resolution. Since I can’t rely on a person to do this properly, automation is the answer.

My first thought was to use something like a PowerSwitch Tail with a microcontroller to trigger it. (There’s also a cheaper kit version available.) The issue with this solution is that I’d need a microcontroller, and a power supply for the microcontroller, which are more parts, and more points of failure, and take up more space. I also considered using a cheap relay module, but ultimately I was overly complicating the whole thing. Also, I want this to be reliable, and sticking a 5v power supply, a microcontroller, and a relay in a box for three years seemed a little risky.

What I really needed was a “Time Delay Relay” which is a device that can get power, wait X number of seconds, and then power on another thing. There’s a whole bunch of them you can just buy! Time Delay Relays are not cheap though… This one is under $40, but you’ll probably also want the socket, which puts you closer to $50.

Luckily, Milwaukee Makerspace is filled with all sorts of old industrial “junk” and we have a bunch of these sitting on a shelf! Brant (you know, the guy who made a Auto-Off Timed Outlets from an old microwave control panel) helped me find one and get it wired up last week. It works great!

I used a $3 extension cord to provide an easy way to plug it into the first power strip and plug the second power strip into it. There’s a dial that lets you set the delay up to 10 seconds, which is more than enough for my needs.

Time Delay Relay

If I’ve learned anything from this project it’s that even though you think you might have a good solution to a problem, it’s still worth asking others (at the space or on the mailing list) because you may get a better solution, and may even get the parts you need.

Auto-Off Timed Outlets

If you’re like me, you’ve left a soldering iron plugged in once or twice.  Hopefully you’re also lucky like me and it’s never started a fire.   Occasionally I’ll grab something off our Hack Rack and take it apart.  A) It’s fun and B) it helps cut down on the ever-growing pile of appliances in the East Room.  Recently I focused my efforts on a microwave oven.  During my salvage operation I managed to extract one plastic fan, two thermal cutout switches, a transformer, the magnetron, a huge capacitor, and the controls.  I soon realized that what I had in front of me was a digital timer wired to a normally open relay.  I couldn’t immediately think of something to do with it, but it seemed too good to toss or disassemble further.  About a week later I decided to wire it to a pair of 120-volt receptacles.  Voila.  Any appliance with a standard plug can be set to run from 00:01 to 99:99 before powering off.  Just press “TIME COOK” then enter the time in minutes and seconds, then start.  The relay closes the circuit and the outlets are energized.  When the timer runs out, a piezo buzzes and the outlets shut off.  The relay on the microwave’s circuit board is 120-250 volt at 16 amps, so I’m fairly comfortable it will handle one or two 40-watt soldering irons.



Refreshing the Singing Pumpkin Display

I’m getting my original singing pumpkin display ready for BVNA’s Pumpkin Pavilion and Halloween. The original display was pure prototype electronics consisting a bunch of stuff from Adafruit: an UNO, a Wave Shield, a PWM/Servo driver, and servos. There was a footprint challenged custom PCB for a TDA7297 and some junk bin DC-DC convertors.


It didn’t look pretty, but it did the job for years. However, the new fully integrated prototype controller looks a lot snazzier.


There are still more design changes to come for this board, but it was really nice to see it perform as intended in my full display.

Let’s Detonate!

Dan Loves Fire!

Dan loves fire! It’s a fact! For Maker Faire Milwaukee we made a fire poofer which was triggered by pressing a button. Tons of kids (and adults) pressed that button over the course of the weekend.

While Dan the Blacksmith (and John McGeen from BBCM) were the primary builders of the fire poofer, I did the trigger electronics and enclosure.

The Detonator

I’ve written up a blog post with lots of images explaining the (somewhat rushed) build of the device. It’s Arduino powered, has some relays and a beeper, and looks semi-nefarious. Read more about The Detonator.

The Detonator Insides