Sunday, November 8, 2020

Star Wars Mind Games

 Riot Games announced a simple board game this year called Tellstones. The gameplay is simple -- my six-year-old picked it up from watching a few rounds. It largely consists of memory and bluffing as the tiles are flipped upside-down and swapped in a slow, deliberate shell game.

The official game features high-quality components and a theme I don't really understand. I rethemed it as a Star Wars game!


I designed symbols for the tiles and engraved them onto black acrylic with a laser cutter. The images really pop once they're painted.


Each tile has blue acrylic glued to its back, which provides a satisfying heft and a neat color contrast when they're face down.


If you have ten minutes, learn how to play and try it out with a few playing cards. You'll find out whether these really are the droids you're looking for!

Ziploc Storage and Fish Feeders

Two smaller projects to share. The first is a simple storage solution for ziploc bags. My wife requested these because the original cardboard boxes didn't fit in the kitchen drawers well.


They fit perfectly and look nice.


An an unrelated note, my son recently got a betta fish. He cares for the fish very well, but I worried about how to feed him (the fish) when we go on vacation (and also my son, I guess). I put together a simple fish feeder that can be attached to the side of the tank.

A small LED blinks to let you know how long until the next feeding occurs. The design consists of a PIC16F15323 microcontroller, a cheap 28BYJ-48 stepper motor, and a homemade PCB. The blue mechanism is 3d printed PETG, which behaves well if it gets wet.

Saturday, October 31, 2020

Halloween Props

Well before anyone question whether Halloween would even occur this year, I thought it would be fun to make a Men in Black neuralizer (or "neuralyzer" depending on the source). Halloween outfits that light up are always a crowd favorite and Mrs. Perry had been asking to do a couples costume idea for several years.

The prop design has changed drastically from movie to movie, both in in shape and light color. Rather than reproducing a specific model that no one would remember, I focused on a simple design with a bright light. Something that would be easy to use at night... and very memorable.

I designed the parts in Fusion 360 and fabricated them on a 3d printer. After some sanding and metallic paint, they'll have the polished chrome look from the movies.

The key piece of electronics is a high-power LED, intended for illuminating outdoor stuff like landscaping. The button instantly discharges the capacitor in a single, bright flash. Like a camera flash, it's brief and leaves you seeing a spot afterwards.

I built two models: red and blue. Very bright, very fun.

We're a rumor, recognizable only as deja vu, and dismissed just as quickly. Happy Halloween!



Tuesday, June 2, 2020

How to Mill PCBs on a CNC Machine

Many of my projects use electronics, requiring printed circuit boards (PCBs). Even if you've never developed electronics, you'll recognize these boards from inside any electronic device you've ever seen. They're covered with electronics and usually green in color (traditionally, board inspections were performs my humans and green provided good contrast).



Although the price of (Chinese) PCB fabrication has dropped considerably over the past decade, it's often beneficial to make this closer to home, saving money and weeks of turnaround time. It's also a fulfilling DIY project if you have the right tools.

Rather than show off a project I've made, in this post I'll explain how milled PCBs are produced using a CNC machine with enough detail that you can try it yourself if you have access to a CNC.

Designing a Circuit

I use Eagle CAD for my circuit design because I purchased a lifetime license back when they offered such things. I believe they still have a free version for non-commercial use, but since they started requiring monthly subscription fees most of the hobby community seems to have migrated to KiCad, an open-source, multi-platform tool. Whatever tool you choose, plenty of tutorials are available online to cover design, which is beyond the scope of this tutorial.



Once you have a design, you'll want to export the layers you care about as a DXF file and import that into your CNC software.

Tools and Materials

All materials can be purchased cheaply from sites like AliExpress, eBay, or, for a premium price, even Amazon.


Firstly, you need copper-clad PCB material. I prefer single-clad, meaning the copper is only only one side of the PCB. If you want to do something fancy, you can try double-clad and worry about the double-sided aligning of CNCing. At the time of writing, a 10-pack of 7cm x 10cm "Single Sided Copper Clad PCB" runs around $7, but the prices have fluctuated upwards quite a bit since the COVID-19 situation started.


For cutting the traces, you'll need at least one PCB V-bit engraver. Now, you may be tempted to purchase a fine 10-degree bit with a sharp 0.1mm tip, but that would be a mistake. Such a fine tip will break nearly instantly and without a microscope you'd never even know it. It'll look fine, but your PCBs will be ugly and won't work and you'll spend hours trying to puzzle out why and when you finally figure it out you'll want to warn others. But you won't be bitter or anything. Okay, maybe you'll be just a little bitter.

What you really want is a 30-degree, 0.2mm tip engraving bit. Tips smaller than 0.2mm will break too quickly and you're not engraving deeply enough for the angle to matter all that much. Search for "PCB V bit" or similar and expect to pay around 35 cents apiece when you buy a set of 10.


You may need a couple different sizes of drill bits depending on what your circuit calls for. Through-hole designs will definitely need these, whereas a pure surface mount design could avoid them altogether. I keep 0.8mm and 1.0mm bits on hand. Despite their size, they last a while unless someone bumps against them. Simply search "PCB 0.8mm" or similar and expect to pay around 20 cents apiece.



Lastly, an edge bit will route the shape of your completed PCB. It's optional since you can simply cut the PCB shape on a scroll saw or by other means, but it's so very worth having this bit. It gives PCBs a professional, finished look to them. These are trickier to search for, but try "PCB edge bit" or see if this link still works by the time you read this. The tip size isn't critical (I have 1.2mm) and these bits last a while. Expect to pay around $1.50 per bit.

Preparing for Milling

It is very important to have a flat, level surface to mill. This means, in additional to leveling your CNC surface, you should ensure the PCB itself is flat. Place it on a flat surface like a countertop and flex it slightly until it lays perfectly flat. You'll find that there's quite a bit of flexibility to the fiberglass substrate.

I like to mill the traces first, since that's the most finicky part. You want to ensure that you're completely cutting through the copper, but not going so deep as to make the traces too small. It also helps to do a lead out, making sure you overcut slightly to avoid any uncut portions at the beginning/end of the trace.



Since there is no silkscreen, I often cut documentation directly onto the board. Drilling is quick and painless. The optional perimeter cut makes the difference between a quick test board (above) and a clean finished edge (below).



Friday, May 29, 2020

3-D Layered Puzzles

I recently ran across a "multi-layer transparent puzzles" Kickstarter project that looked fantastic. The idea looked fun and the creator even provided instructions on how to make your own, so I did just that.


The first step was choosing a design and slicing it up among three separate layers. This took longer than I thought, but resulted in a unique design with a fantastic aesthetic.


I laser cut these out of clear and red acrylic. The pieces combine into three separate puzzles. Separately, the layers appear chaotic. The puzzle is rather challenging (it's difficult to gauge how challenging the puzzle will be while designing). If I do another, I'll probably use fewer pieces and I'll definitely avoid any nearly-symmetric pieces, since it's hard to know if a piece is flipped when it almost fits both ways.


Once stacked on each other, the full design emerges. It's a beautiful effect and sits nicely on my desk until I decide to challenge jumble the pieces and puzzle it together anew.

Thursday, May 28, 2020

Word Clock

Analog clocks are hard for most kids to read. Binary clocks are difficult for most adults. Word clocks, on the other hand, are effortless. Just read the displayed sentence: "It is eight fifteen".
The camera records this poorly.
In person, the display is sharp and easy to read.





















The display consists of an LED matrix with a PCB light might in front of it, an idea which I first saw on Hackaday. Determining the proper arrangements of letters was a fun challenge that took ages, especially since I wanted the clock to display holiday messages as talk about later.


















The primary PCB has all the electronics on it. Here I'm debugging the LEDs, which didn't work for months. I gloss over this in most of my blog entries, but most projects have tons of aggravating problems during development.

















Once the LEDs were working, I needed to design a spacer between the PCBs and a stand to hold it upright. I used a CAD tool for the design and a 3d printer for the actual pieces. 80 degrees felt like a good angle and, if it wasn't, replacement feet are quick to print for other angles.


The clock is powered by a USB cable. It has a backup battery (actually a supercapacitor) that keeps track of the time and date for up to a week without power. When it powers up, it cheerfully declares, "I am a clock" before telling the time.

On holidays, it displays abbreviated holiday messages like, "H-a-p-p-y  m-o-m-s  d-a-y" for 21 different holidays, plus a birthday. Figuring out the perfect layout for this was tricky. Some holidays are simple (Happy MLK Day) whereas one or two require some creativity (Happy Scare Day because "Halloween" is too long).

Sunday, March 29, 2020

Pong Arcade Clock

A Pong clock is something I've wanted to make for around a decade. It's a fun Pong demo of two computer player competing. The right player scores every minute, while the left player scores only once an hour. The score tells the current time.

Most variations of the idea feature stiff, unrealistic computer players. They perfect track the ball constantly except when they intend to miss, at which point they avoid it almost to the point of comedy. I spent time watching human players compete in the game and taking notes how how they behaved. Humans overcompensate, estimate and err about where the ball will land, and tend to overshoot when they eventually miss.



I designed a PCB, milled it on my CNC machine, and attached it to an LCD. Incidentally, that's the same display from the old Nokia 5510 phones. They still make these in China where they're cheap and very energy efficient. I would have liked a color display, but the power draw wouldn't support a constantly running clock.


For the enclosure, I designed a miniature arcade cabinet using Fusion 360 and 3d printed it. It took a long time to design to satisfaction, but the aesthetic is totally worth it. It really brings the clock together in a fun way.


Of course, you can't build just one. Most of the work was in the design, so assembling a second one didn't take long.


For added fun, I included some playable games based on Nintendo's Game & Watch series from the 1980s, one of which I owned as a child (thanks, Mom and Dad!). I've recreated both Ball and Vermin as playable games on the miniature arcade. Check out the pong clock and the games in the video below.

Tuesday, March 24, 2020

Stylish Binary Clock

The geekiest clock that I see with any regularity has to be the binary clock. It's usually just a series of LEDs and it's not uncommon to see commercial USB models on engineers desks at work. For several years I've idly considered building one, but couldn't think of a way to make one that wasn't just ugly.

That changed when I got a 3d printer and laser cutter, opening up a myriad of potential enclosure ideas. A couple years ago, I saw a Kickstarter project that showcased the perfect housing: something that looks so decorative that you'd never know it was a clock!

I purchased a vector file from Etsy and used my CNC software to nest the vectors so they'd use less material. I cut it using my new craigslist find: a laser cutter.




It used roughly a sheet and a quarter and was kind of fun to assemble together! I wouldn't have thought to put pieces together so artistically, so I'm glad I purchased the vectors for this.


I milled a PCB on my CNC machine. I realize now that I've never showcased this process outside of a brief mention on my weather station, so I'll need to remember to go into detail on a future project. The brains are a simple microcontroller, watch crystal, and buttons for setting time/configuration. The windows are covered with vellum paper.


All assembled, it looks great! To the casual observer, it's a cute little house with lights that occasionally change. To the geek, it's also a clock. If I ever make another one, I'll probably paint it before assembling it.


For festive occasions, I added a variety of color combinations: pastels for Easter, reds for Valentines Day, etc. You can see the Christmas and patriotic (July 4th, Flag Day, etc.) displays below. The colors are randomized and sometimes change when you're not looking.




Technical Specs for Geeks
LEDs are a simple WS2812B (IP30) strip cut into pieces.

MCU is a PIC24FV16KA301, which is 5-volt tolerant and supports my PIC24 WS2812B code. Firmware & buttons allow for brightness control, clock calibration (so it runs the right speed), and color schema selection.

Color schemas include
  • warm white
  • Valentine's (reds/pinks)
  • Easter (pastels)
  • patriotic (red/white/blue)
  • St. Pats (greens)
  • Halloween (orange/purple/green)
  • Thanksgiving (fall colors)
  • Christmas (red/green)
  • "unicorn barf" (random colors)

Sunday, March 22, 2020

Flip Clock Repair, Cordless Adapter, and More Funny Shirts

It's a mid-year "Odds and Ends" entry, starting with a fun flip clock that my brother gifted me for Christmas a few years back. One of the flip panels broke several months ago. Unfortunately, it's a critical panel--the one that's supposed to prevent the hours from flipping until the minutes wrap from 59 to 00.

I suspect a bad design put continual stress on this panel until the tab broke off. Among all the panels, this one is unique, so I'm not surprised it broke first. It also means I can't just leave it out (the clock would advance from, say, 3:56 to 4:56, then 4:57..4:59 and finally 4:00... ugh!). And I can swap it out for a different panel. Instead, I 3d printed my own and painted it up.


The replacement is actually thinner than the original.



It works great!



Cordless Adapter
While we were repairing fences, my neighbor mentioned (again!) how convenient it would be to have an AC adapter for his cordless tools. He wanted to be able to use them even when all the batteries were dead.

I gutted a dead battery pack, wired in an adapter plug, and purchased an AC adapter with matching specs. Not a big project, but he was very happy with it.



More Funny Shirts
It's been a while since I first made the vinyl cutter or any additional shirts on it. I put together a few designs that I thought would be fun for the family.


The middle shirt is my first attempt at multiple vinyl colors. It came out nicely!


I had hoped to amuse my parents with some of these on our vacation next month, but Coronavirus put a stop to that plan. At least I can wear them during the week as I work from home.