Moon Tower Defense

2019 Critical Northwest art festival project

Remote fire effect tower in river – the main reason we went for wireless communications.


Imagine sitting atop a tower in an inviting swivel turret with firehose style water cannon pointed out across the river waiting to soak river riders at the push of a button on at hot July afternoon. But wait… whats wrong? No pressure? Better bring some friends to bring the dance vibes and activate the cannon.

But by night it’s too dark to aim. So the LEDs come on, the fire towers come alive and the night fills with flickering, dancing shadows.

Design challenge

Actuators and sensors are located in a river or atop a tower. Their code needs to be simple and rarely changed. One master “brains” controller is kept easily accessible and can be reprogrammed frequently.

Additionally cabling needs to be minimized somehow as distances are considerable. So we went with WiFi for our communication network to avoid long Ethernet or other cable runs.

Technical details

  • IoT technology, though we don’t have it actually hooked up to the internet
  • MQTT for communication
  • ESP8266 for each sensor or actuator. Many cheap processors handling individual tasks
  • 802.11 WiFi for network
  • C++ with the Arduino IDE


  • one is the brains listening to all the inputs and issuing output commands
  • some are simple sensors like a button and simply transmit their state
  • others are effects controllers and respond with light or fire to animation commands from the brains
  • several are motion sensors that detect people


by Potluck

Shadows at Burien Arts-A-Glow, 2017. Photo by Patrick Robinson –

An equilateral triangle is suspended, point down. Light and sound are responsive to the participant’s location and movements, animating the sculpture. Together the participant and the sculpture become the art.

Our aim was to design and build an interactive light and sound sculpture with a simple yet dynamic control with bonus points for being light, easy to transport, and easily assembled.

The “Shadows” title is a play on the geometry and animation.  The lighting animations appear as if a participant’s arm were casting shadows from point-source lights in each corner… if the shadowed areas were bright and the not-shadowed areas were dark.  “Inverse Shadows” might be a more proper name, but either is too-clever-by-half and fails to capture what we’re doing with this. Moral of the story: never let engineers name things.

The brains of Shadows is a Moteino Mega, an Arduino clone with built in radio. We wrote custom code to read the three MaxSonar ultrasonic rangefinders, one in each corner of the triangle, and calculate the location of the object within the triangle.

Sounds corresponding to the distance to each corner are triggered by commands to an off the shelf audio board capable of playing sound clips from an SD card over a simple headphone jack.

Each light tube has a Moteino to receive location information wirelessly from the master Moteino and to calculate and display its animations on two strips of individually addressable LEDs.

More technical details can be found on our GitHub page.

Shadows was shown at Kiwi Burn 2017 in February, Critical Northwest 2017 in July, Lusio, Seattle 2017, and will be at Burien Arts A Glow in September 2017.

Email Brian at briandernst at gmail.


Seven origami cranes in steel stand ten feet in the air. Lit with LED spotlights and animated LED strips, Nozomi invites the public to wander at night among colorful, brightly lit, whimsical shapes. Nozomi was funded by Ignition Northwest and donations from the community and was shown at Burning Man and Critical Northwest 2012.


I designed and fabricated spot lights featuring a high power LED driven by a constant current source for power efficiency. Spotlights were chosen for several cranes to highlight stark arrangements of geometric shapes or monotone covering material.

Continue reading Nozomi

Ablation Cascade

A series of nested concentric rings mounted on independent bearings allows participants to spin the rings in all directions. Ablation Cascade seeks to evoke the orbits of satellites and remind us of the unseen space debris high above. Ablation Cascade was funded by Ignition Northwest and donations from the community and was shown at Burning Man and Critical Northwest 2013.



Designed to be a gathering space offering shade and a view by day and contributing to the lit skyline by night with its animated electroluminescent lighting effects. Arborealis was funded by Ignition Northwest and donations from the community and was shown at Burning Man and Critical Northwest 2010.

arborealis at night

Arborealis dawn