pololu

It’s The Detonator! What is The Detonator you ask? Well, for Maker Faire Milwaukee we build a fire poofer, which is a device that shoots flames into the air. Workmate John McGeen started the poofer build and we finished it up at Milwaukee Makerpace. Along the way we experimented with a torch, candles, and grill igniters, until Dan the Blacksmith finally added a pilot line and some steel wool.

Fire Poofer

The Detonator went through a few revisions, but I’ll walk through the construction of it for this blog post. We brainstormed a few different ideas to trigger the poofer, but in the end I went with something simple than I knew would work reliably for the entire weekend. (And it did!)

Laser Cut Parts

I started by using MakerCase to design a box I could laser cut. I used 3mm black acrylic because I have a lot of it, and I made the box the size that worked with the acrylic I had. The image shows the acrylic (gray parts) and one piece of 1/4″ wood (which is tan in the image.) The wood piece went on the inside, right under the top acrylic with the hole for the button.

Since I wanted The Detonator to withstand being pressed, slammed, and pounded on by hundreds of people over the course of two days, I also built a wooden box that fit inside the acrylic box. This added strength and weight to it.

Vinyl

I didn’t just want a plain black box, so I added some bright yellow vinyl to it. I cut the vinyl with a Silhouette Cameo. The image above shows how I determined wrapping the vinyl around the edges.

The Detonator - Vinyl

Here are the vinyl pieces I cut. I added cut outlines around the pieces so I’d be able to line it up correctly. It worked pretty well. (I didn’t take time to measure or mark things, but that would be a recommendation.)

The Detonator - Illustration

Above is my final “pretty” illustration of The Detonator. Below is a very black photo of The Detonator. I’m fairly pleased with how it turned out, especially since it was a rush job to build it.

There are four connector posts, but only two got used in the end. I originally had just the two in the center, but ended up splitting them and adding extra posts so I could split power between 12 volts (well, 18 volts, sort of) for the solenoid, and 4.5 volts for the grill igniters. We ended up ditching the grill igniters, so in the end I only needed one pair of connectors. Oh well!

The Detonator Guts

Here’s the inside! There’s a Pololu A-Star 32U4 Micro mounted on an Adafruit Perma-Proto Half-sized Breadboard PCB with some screw terminal connectors, which is connected to a relay board. The board I used had four relays, but since we didn’t use the grill igniters I could have used a two relay board. (Also, relay boards are super-cheap on ebay.) There’s also a relay controlling a beeper that beeps a countdown. (See the video below.)

Overall The Detonator was a quick build. and there’s a few things that could have been a bit more polished. For instance, I cracked the acrylic a bit when I drilled more holes for the connection posts. In an ideal world I would have laser cut a new piece, but I didn’t have time. I also could have made the code a bit simpler after removal of the batteries for the grill igniters, but hey… The Detonator turned out good for a quick fire poofer controller!

Teensy is teensy

For the past few years I’ve been building devices that can emulate computer keyboards. Typically I’ve used the Teensy microcontrollers for this along with the Arduino IDE and the Teensyduino add-on. The things you can do with a Teensy to emulate a keyboard are very impressive! Basically, it’s the best way I know of to create your own custom USB keyboard.

Size matters – A-Star with Arduino Micro and Leonardo

When the Arduino Leonardo was introduced, one of the features I was interested in was the ability to emulate a USB keyboard. I never actually got a Leonardo to test this with, mainly because the form factor was too large for my projects. Sometimes shield compatibility is good, sometimes the smallest board wins.

Size matters!

I recently got a Pololu A-Star 32U4 Micro, which is a tiny (and cheap, under $13USD) board very similar to a Leonardo, once again using the Atmel ATmega32U4.

There may be a little bit of work involved in getting the A-Star up and running. There are drivers needed if using Windows, and (supposedly) a little more work to get things going with Linux. I had no issues with Mac OS X, but I’m pretty familiar with add-ons for the Arduino IDE due to using Teensyduino. You can also just pretend this is an Arduino Leonardo and that seems to work fine.

(I also can’t tell if the Pololu A-Star 32U4 Micro is open source hardware. They do have a bunch of files available, but I did not see an explicit “Open Hardware” note anywhere. It’s worth mentioning that the Teensy is not open source hardware. If that’s not a big deal to you, then it’s not a big deal to you. The official Arduino hardware is of course, open source.)

I’ll probably keep experimenting with the Pololu A-Star as a keyboard emulator for simple things, and stick with the Teensy for more complex things. I’ve also heard that the Teensy 2.0 will disappear in the future, which isn’t a huge deal, as the Teensy 3.1 is a big improvement over it, but the 3.1 does cost a bit more than the 2.0, so that’s one factor to consider when evaluating which board to use.

Have fun building your own keyboard!

Update #1: I’ve been talking to Pololu and they suggested the A-Star may actually be able to use the Teensyduino Keyboard libraries. I’m awaiting more info on this, as it would be an exciting development.

Update #2: It looks like the Teensyduino Keyboard libraries cannot be installed onto the A-Star, which is good to know. But don’t worry, I’ll be using the A-Star for some future projects anyway. ;)