Seattle Mini Maker Faire 2015 and the Arachnio Due

This year's Seattle Mini MakerFaire was really exciting for us because we got to show off our upcoming product, the Arachnio Due! The most common comment I received about the original Arachnio is that it needed an ARM chip. I took  that to heart after we didn't reach our original funding goal and I'm proud to introduce the Arachnio Due, with replaces the earlier ATmega32u4 with an Atmel SAM4S, which is an ARM Cortex-M4 running at 120 MHz.

Check out our project progress on or sign up for our mailing list to receive notifications when the Arachnio Due is ready to launch on Kickstarter.

In order to show off the Arachnio Due, I built a pair of sumo bots using the cellphone control code Jeremy wrote for the original. The EMP event folks are very cool and helpful, and were able to get us a nice round table to fit our playing field (laser cut at Metrix Create Space) at nearly the last minute.  

The sumo bots were really popular, and it was great to see people really get how cool it is to have an Arduino variant that can connect to your phone or any other wifi network. I built them with the cheap Tamiya dual motor gearboxes, so they needed a fair amount of maintenance -- Alex did a great job keeping them running through most of the fair. 

Our booth during setup. We got another table and a fence around the playing field on the right. 

Our booth during setup. We got another table and a fence around the playing field on the right. 

The Arachnio sumo bots on the play field, ready for action! The Arachnio Dues are the green boards with blue lights. The driver boards were created for these bots, and will probably appear in the Kickstarter as a stretch goal.

The Arachnio sumo bots on the play field, ready for action! The Arachnio Dues are the green boards with blue lights. The driver boards were created for these bots, and will probably appear in the Kickstarter as a stretch goal.



My son pushes my bot out of the ring.

My son pushes my bot out of the ring.

The Couch Armada arrives to check out the Arachnio Due

The Couch Armada arrives to check out the Arachnio Due

Classes at Metrix Create:Space

I'm teaching a number of workshops at Metrix this winter that some of you might find interesting.  Here's the schedule:

  • Intro to Arduino covers the basics of using the Arduino. It covers setup, introductory programming, and simple interface circuits. Cost is $70 and includes an Arduino and all materials. Each student needs to bring a laptop. It will be offered on the following days:
  • Intro to Electronics covers basic electronics concepts and simple circuits. $60, materials included. 
  • Mobile Sensors will cover the basics of the most popular types of sensors used in mobile and wearable applications: force, position, light, temperature, tilt, compasses, and more. These types of sensors can enable you to build things from an automatic night light to a
    robot capable of navigating through a room on its own. The Arduino platform will provide a handy tool for recording, analyzing, presenting, and acting on the sensor output. Finally, each student will have the opportunity to build a sensor-enabled device with the Arduino platform.
  • Digital Communications with Arduino delves into expanding the capabilities of your Arduino by using the built-in communications ports to talk to various kinds of peripherals! We will be exploring common communications types including I2C, SPI, serial, and shift registers. Students will receive an Arduino shield with examples of peripherals that use each communication type. Students need to bring an Arduino-compatible board and a laptop. Students should be familiar with the material in Intro to Arduino. Cost is $100.

Zigduino on Arduino IDE 1.5

I finally got around to porting the Zigduino files over to the Arduino-1.5.7 IDE... and it is wonderful.

Instead of being somewhat painful to install like the previous versions, it's just a zip file that you unpack in to the $SKETCHBOOK/hardware directory and restart the IDE. The Arduino-1.5.7 IDE also uses a current avr-gcc toolchain, so no mucking around with that either. I've pulled the ZigduinoRadio library into the distribution as well, so the new process is as follows:

  1. Download the zipball from Github.
  2. Unpack the zipball into the hardware subdirectory of your Arduino sketchbook directory
  3. Start the Arduino-1.5.7 IDE

And that's it!

RGB LED Matrix Customer Projects

A couple of my latest customers for the new RGB LED Matrix Backpack have done some pretty cool things with it. 

Steven programmed a gorgeous multi-color bouncing ball interaction with the aliasing tricks to increase the apparent resolution. This is one of the nicer video clips I've seen -- shooting things that glow is difficult to do well and Steven did a nice job here. 

Charles put together a neat little printable 3D snap-action clip that makes it really easy to connect backpacks together to build arrays of LED matrices. You can find the model on TinkerCAD.

Another op amp parameter to pay attention to...

I recently managed to build a non-inverting amplifier with an op amp that acted as an inverting amplifier. I found this more than a little puzzling, and asked around for possible causes. My friends were kind enough not to laugh too much when they pointed out my error. 

The problem was that the op amp I had selected, the TL974, has a rather tight common mode voltage spec. It expects the common mode input voltage to be more than a volt from each power rail. The common mode voltage is the average of the two input voltages. Since those voltages are equal (or nearly so) in the non-inverting configuration, we can assume that the common mode voltage is equal to the input voltage.   

The input voltages on my circuit ranged from 0-1.8V against power rails of 0V and 3.8V. Not surprisingly, this didn't work very well; it caused the inverting and non-inverting inputs to swap places. As a result, instead of amplifying the input voltage across the intended gain of two, it shifted the signal up 1.8V and inverted it. Wheeee!

Here's a long but useful discussion of this issue on Planet Analog.

Circuit pattern trading cards

Arachnid Labs has come out with circuit pattern trading cards. Most electrical circuits are composed from a relatively small number of common patterns that can be designed and analyzed as units. The engineer can then compose these individual sub-circuits into a completed device.  

Arachnid Labs took this and produced a set of 32 trading cards that illustrate some of the most common ones. Once you recognize these patterns, you will begin to see them in every schematic you see.


New website!

If you haven't visited our website in a while, you may notice that it looks much different. That's because we've re-designed it and switched from Google Checkout over to Stripe for handling credit cards and the like. It doesn't require your credit card to be attached to your Google account in order to use it, which should help some of our institutional customers. 

We've tried to duplicate as many links from the old website as made sense. Please poke around and see if we've missed anything important. 

Come see us at Maker Faire Bay Area 2013!

It's that time of year again -- time for Maker Faire Bay Area! We'll be sharing a booth with the Metrix Open Hardware Alliance, which is a coalition of several Seattle-area open source hardware companies, including OpenBeam USA, organized by our friends at Metrix Create:Space. We'll be in booth 514, in the southeast quadrant of the Expo Hall.