If you’ve ever used a potentiometer you know it can only turn so far. About 270 degrees of rotation is what you get out of most potentiometers, which is plenty. The problem with using potentiometers in museum exhibits is that while adults (typically) know that when the knob stops turning you should stop turning the knob, kids don’t always know this. Kids are notorious for going too far when it comes to physical controls.


So I’ve been working on a way to use potentiometers in an exhibit, but hide them down below in the cabinet, and expose a control knob to the surface that has limited rotation. About 220 degrees of rotation. I could do more, but the idea of using less than 270 is the key. If we don’t get too close to the beginning or end of the rotation limit, we should be able to prevent the potentiometer from being twisted too far and becoming damaged.


I drew up the parts needed to build an encased knob with a hard stop inside. In the final version the knob will be machined from HDPE plastic using a CNC router. I opted to 3D print the pieces for the prototype because it was quick and easy. (“Quick” is relative, of course, but I finished up the drawing and got the model printing at the end of the day, so the printer did the work overnight while I wasn’t there.)


I drew all the pieces in Inkscape and then exported DXF files and brought them into OpenSCAD and extruded them to 1/4″ high. There’s a 1/4″ hole in a few pieces (and a slightly larger hole in the bottom piece) so that a 1/4″ steel shaft can be inserted. The shaft will be connected to the potentiometer. (I made a 3D printed prototype of that too, which you can see here and here.)


Here’s an exploded view of the assembly. Sometimes it’s tricky to design things like this using flat 2D shapes in Inkscape, but I’ve gotten used to it, and I think I’m pretty good at it. I should mention I also printed a paper prototype to help figure things out along the way. (And yes, the original plan was to laser cut the pieces out of foam core which would have made the most sense, but the laser cutter was not available when I did this.) The fact that I created 3D models did allow me to make the nice exploded view very easily.


Here’s a quick assembly using hot glue. Just to test how it worked, as well as get a feel for the size of it. (I’ll have a follow-up post about the layout of the whole panel.)


HDPE can’t really be glued, so we use screws (hidden when possible) to attach layers. We may be able to get away with fewer layers than I used here, because I used 1/4″ layers, but it might make sense to use 1/2″ or 3/4″ layers since we often get HDPE in those thicknesses. And of course we can pocket things out, and not just use a flat stack. (Again, this is a prototype.)


I finally got around to 3D printing on fabric. It worked out okay. I need to experiment a bit more to perfect it, but for a first attempt, it worked out okay.


I used OpenSCAD to design a bump, and then made a field of bumps. (It’s a low-poly half sphere, actually. Really simple to do in OpenSCAD.)


Also really easy to generate a bunch of them in OpenSCAD by using two for loops. I know OpenSCAD isn’t for everyone, but if you think in code, it might work for you.


I used this organza fabric to print onto. It’s a mesh material, so the process of printing on it involves printing a few layers, then pausing the print, moving the print head out of the way, laying down the fabric, securing it to the bed, then continuing the print. The fabric gets embedded within the layers of the print.


My Maker Select Plus did not allow me to pause the print and move the extruder using the on screen controls, so I added some custom gcode to my print. Cura has a post-processing plugin that allows you to inject gcode bits into your script. I had make an edit to get it to work with my printer. And then I actually made my own version so I don’t lost the changes when I upgrade Cura next time.


So what use is this? It allows you to wrap a print around something. It an be used to create fake armor for cosplay, or to wrap anything cylindrical, or add an interesting texture to something. Over at Milwaukee Makerspace we may have something in the works for Maker Faire Milwaukee this year.

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Stay Tuned!


It’s been a while so it’s time for another RepRap Report! So what’s changed since last time? So much… I’ll try to hit it all.

I got rid of the BuildTak and moved to a PEI Sheet. I upgraded to the Micro Swiss All Metal Hotend which made printing ABS reliable once again.

I repaired fans, I replaced fans. And then I did it again. Once I got ABS printing up to speed I printed a DiiiCooler, which I finally installed, and still haven’t used (since I’m printing ABS at the moment.) And yeah, I’m waiting for some new extruder fans to arrive after last night’s hurried soldering session to repair another bad fan.


If all of this seems silly, well, in a way it is, and it isn’t. When you buy a thing (be it a 3D printer or a car) you can go cheap knowing that things might break or need upgrades, or you can pay a lot more for quality out of the gate, with the hope that things don’t go wrong or are of a higher quality. I knew that getting the Monoprice Maker Select Plus meant compromising so I could afford a printer (which was replacing my old RepRap Prusa i2 kit from 2011) and I was fine with that. There are many routes you can go with a printer. I’m going the “cheap” route right now, I’ve got friends who work for the “expensive but reliable route” companies, and then there’s the custom build route. They’re all legit choices.


Oh, I don’t think I ever mentioned my enclosure. It’s built from foamcore board and covered with the packing foam that the printer came in. The front window is a piece of Polycarb I got from Amazon. It works. It’s not pretty. That’s okay. Besides keeping the heat in, it keeps the cats out. Also important. I also added a set of 12 volt LED lights with an on/off/dimmer switch.


If I had to build an enclosure again (and I might need to soon) I’d probably go with foamcore again, but take some effort to make it look good this time.


I still feed the filament from a metal rod hanging above my printer in the basement. It works fine. It’s not portable, and that’s probably okay. The drybox I was working on failed, and I haven’t had the energy to revisit that project. That’s okay for now.

Besides all that, I’ve been printing thing just. Nothing too exciting, but that may change soon. Happy Extruding!


I’ve been messing around with NeoPixels quite a bit lately, and I wanted a small portable light I could use to show off a few “makery” things. So the Brinn Labs Hexalight was created.


It consists of a 3D printed base made from black PLA filament. It was close to a ten hour print, one of the longest I’ve done on my Monoprice Maker Select Plus 3D printer. It turned out well. There’s also a piece of laser cut Acrylic for the top…




I only had clear Acrylic handy, and I experimented with a few ideas for light diffusion (including sanding the backside of the Acrylic, and using some HDPE from a milk jug) but in the end I just left the protective backing sheet that comes on the Acrylic in place. (There’s one small tear in it, though next time if I do this I’ll be more careful ahead of time since I’ll have a plan in place.)


Some slotted pan head screws hold the top in place. I would have preferred some nice hex hardware (obviously!) but didn’t have any on hand, and wanted to complete this build quickly. (Maybe I’ll change it out in the future.)


There’s a piece of scrap wood inside that holds the NeoPixels in place. The wood is not laser cut, but hacked up using a band saw. It’s “good enough” for a hidden piece. (Sometimes I work on projects in multiple places and have to use whatever tools are available at the time.)

The three strips of three NeoPixels each is about what I could fit inside. The strips run in parallel, so there’s not a lot pixels to work with. It also makes the transitions not super-smooth, though I still need to play with the code a bit more.


Here’s a shot of the inside from the back/bottom. It’s messy. There’s an ATtiny85 on a board I’ve used before. This allows for the chip to be removed and reprogrammed. Yes, you can skip an Arduino and use an ATtiny85 for small simple NeoPixel projects. (And still program them with the Arduino IDE.)


There’s a pair of wires that lead out a channel in the back/bottom and go to a barrel jack connector. I can then power it with a 5 volt power supply, either from a wall wart or a USB battery.


BLHexalight v01C

I modeled the 3D printed part in OpenSCAD. It’s easy to make hexagons, and I just added a large squarish hole in the middle for the electronics.

BLHexalight v01B

The red piece is a block I used to do the boolean difference for the main piece. This allowed me to slice the hexagon at a specific angle so I could just end up with the part I wanted.

BLHexalight v01A

Here’s a view of the final piece viewed from the front. You can also see the little “shelf” I made for the piece of wood holding the NeoPixels to fit onto.

BLHexalight v01D

Here’s the model from the bottom. There’s the channel for the power wires to run out of. This was just another boolean difference with a cylinder this time to create a half circle channel.


I used the Silhouette Cameo to cut a piece of black vinyl to put on the front so the logo could light up. Getting the vinyl perfectly aligned was a little tricky, so next time I might try another method. (Or just do a better job.)



This project started like many of my projects… Someone says something, and I have a reaction to it. I might say something, or I might not say anything, but I’ll get an idea, and decide to do something. Sometimes it’s a ridiculous idea, and that doesn’t really matter. In fact, ridiculous ideas are probably more likely to be explored.


This one started when a local teacher got in touch with Milwaukee Makerspace about donating a bunch of industrial control equipment. Luckily Tom and a few other members were interested enough to go look through nine boxes and transport them back to the space so members could look through them. I should note this is a common thing. When people want to get rid of things we look for a “Champion”. Basically someone who will take responsibility for the stuff. If they bring it to the space we ask that whatever members don’t take “goes away” within a week or so. (Typically this means the dumpster, but not always. At a minimum, some members take some things and divert them from the landfill. Sometimes things are donated to others or recycled.)


This load was a bunch of industrial electronics. Not super useful for most of our members, but many did find some good things. I found some neat switches, and in particular this large switch with a nick “CLUNK!” sound that said it was capable of handling 690 volts…


Steve and I were looking at it as I clicked it on and off and I mentioned how many volts it could handle and he said “Hey, you need to make it turn on an LED!” which was (probably) a joke, since an LED requires roughly 3 volts, which is quite a bit less than 690 volts. (In fact, it’s approximately 687 volts less!)


So I did what I had to do… I had to assemble the switch into a device that could turn on (and off) and LED. I had also found (and destroyed) an old data tape, but I managed to save the nice Aluminum plate that served as the base of the data tape. (Seriously, some of those old tapes were sort of beautiful!) Since I now had to weird objects, I just combined them with some wire, an LED, and LED panel mount, a battery holder, and two AA batteries. The rest is… history!?


There’s also a Sintra plate on the bottom that the battery holder screws into to hold it in place. And some tape, and some hot glue. (It’s not a project until you add the hot glue!)


So yeah, it’s a but ridiculous, but it’s also somewhat interesting. In some of my projects I don’t even add a switch. This actually seems very common in “maker” projects. Why add a switch when you can just apply and cut power by plugging a thing in!? So why not make the switch the BIG THING in the project. Many times larger than the batteries and the thing you’re actually turning on. Hell, it’s almost art!

Because the switch sounds so amazing, I had to make a video. Oh, also you can see the LED turn on, so there’s no trickery in this video.

Also, worse case, if I keep this thing around I’ll have a nice big high voltage rated switch I can cannibalize for another project. So that’s a big win in my book.

(Oh, sorry about the terrible photos of the blue LED. I need to do better next time.)

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