at Control-H, 7608 N. Interstate, Portland, OR 97217
Sunday, Sept 27th, 2015 1-5pm
The Oregon Lawnmower Massacre is post-pwned by mechanical issues.  So come to Ctrl-H and hack on your current project, offer help to others, or just hang out!
We provide space and power.  You bring tools and projects.  Ask fellow dorks for help and offer help to others.

DORKBOTPDX September 2015 Workshop: Oregon Lawnmower Massacre

Unfortauntely this workshop has been post-pwned due to mechanical issues, please come to Ctrl-H for a free Open Lab Sunday September 27th instead!

In this workshop we will build a "kicking legs" Halloween prop.  These props are normally put under lawnmowers to simulate a lawn care accident.  This project is based on a project by "Scary Terry", you can see the original here.  We'll play with linkages, servos, and microcontrollers.
Here's a quick video of the mechanism (not final though). 

  • Laptop with Teensyduino installed
  • Phillips head screwdriver (electric is probably best)
  • 2 wrenches, either 7/8", 11 mm, or adjustable
  • A pair of socks, old shorts/pants, fake blood, etc for decoration.
  • $35 for the kit.  Comes with:
  • Optional: Switches / sensors to trigger the kit
RSVP required!  RSVP by emailing
Sunday, September 27, 1-5pm at
All ages!
Donate to Ctrl-H if you can!
Flyer by Jason Plumb

Sturdy Pots on Breadboards

Often I throw together a quick demo for the bi-weekly DorkbotPDX meetup, usually involving one or more pots to adjust parameters.  Finally, I've come up with a pretty good way to put pots on solderless breadboards.

Click "Read more" for details and the shared PCB....

DORKBOTPDX July 2015 Workshop: Undorked Aerial Vehicles

Rich Burton of HooperFly gives an overview of open source drone/uav projects and flight demonstrations. We'll take a group dronie! 
Here's a link to the slides:
Sunday, July 26th, 1-5pm at
Everyone welcome! All ages!
Free! (Donate a bit to Ctrl-H if you can)
Flyer by: Zach Archer
More links for post:

Solar Power Charger Workshop


DORKBOTPDX June 2015 Workshop: Solar Power Charger Workshop

Experiment with solar panels and the other bits needed to charge Lithium Ion batteries via USB.
Sunday, June 28th, 1-5pm at 
Free! (Donate a bit to Ctrl-H if you can)

Teensy Audio Library Gets S/PDIF Support

Thanks to the amazing effort of Frank Boesing, the Teensy Audio Library now has native S/PDIF output.

Using a $1 TOSLINK connector, or just a red LED, you can get optical S/PDIF digital audio output.

Optical output is useful for projects where Teensy connects to grounded equipment.  There are lots of ways to simply play sounds, but the Teensy Audio Library gives you Arduino-sketch controlled synthesis, mixing, effects & filters, analysis and much more.  Sketch controlled sound is most useful when you connect more hardware to Teensy & use other Arduino libraries for inputs.  But often that other hardware comes with ground connections that cause audio-corrupting ground loop problems with analog audio, like the DAC pin or the audio shield.  Optical S/PDIF give you perfect digital audio output for those projects!

Click "Read more" for much more detail about the S/PDIF development....

Ten Watt RGB LEDs

Spent a good portion of the weekend fiddling with insanely bright 10 watt RGB LEDs.

Trying to make very low-cost DMX protocol control, of course for a Burning Man project that's planning to use 150 of them!

DorkbotPDX May 2015 Workshop: OPEN LAB!


at Control-H, 7608 N. Interstate, Portland, OR 97217
Sunday, May 31, 2015 1-5pm
While having a single teacher and many students helps get ideas and skills out to the community, sometimes it is more fun to have some chaos.  So instead of one to many, we'll have many to many.  Bring a project or collaborate on someone else's project.
We provide space and power.  You bring tools and projects.  Ask fellow dorks for help and offer help to others.
RSVP by replying to this page and telling folks what you'll be working on!

Control Voltage (CV) to Analog Input Pin

Often I've been asked how to get synth control voltage (CV) into an analog input pin.  Teensy 3.1 has 13 bits effective analog resolution, good enough for many CV applications, but the stable internal reference is only 1.2V with analogReference(INTERNAL).

This simple circuit converts the -5V to +5V CV signal range to the 0 to 1.2V ADC input range.

Edit: here's a discussion about this circuit's details and limitations (fancy opamp-based circuits can be better).

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