Introduction: Vote With Your Feet

Have a question for your fellow citizens and wonder how they'd react? We made an art installation for just that! "Vote With Your Feet" is a public installation that asks questions for citizens, and get answers from citizens.

Two doorways stand in the middle of the sidewalk, with a question displayed on a sign above them. Each door stands for an answer. The installation counts the number of people that walk through each door. Once you walk through the door, you can see the results on the door, and online at

The installation was live on Market St during Market Street Prototyping Festival ( and had more than ten thousand votes in 3 days. We were excited to see what San Francisco thinks. We're also fascinated if you duplicate them in your city and test it out, so we can compare notes!

The project composes of three major parts:

I. The construction of the door

II. The control of the flipdot display

III. The data logging and visualization

We will focus on Part I in this instructable.

Step 1: Planning

I designed the entire structure on Fusion 360. The design can be viewed and downloaded here

Your design will entirely depend on the tools you have at hand, and the budget and esthetics.

At Pier 9 workshop ( , I have the luxury to use the following :

  1. OMAX Waterjet (
  2. Shopbot full-size PRSalpha (
  3. Millermatic 252 Mig Welder (
  4. Bridgeport Series I Standard knee mill (

  5. Roland Versacamm Wide Format Printer (

  6. Spray booth

  7. Epilog laser cutter (

  8. Electronics lab (

  9. drill press (

  10. sander (

Given the machines available, here is my material list:

  1. Aluminum Sheet 4'x6'x1/2"
  2. Steal Sheet 2' x 1' x 1/4"
  3. Square Steel Tube 3"x3"x6' (2 tubes)

  4. Plywood 4'x8'x3/4"
  5. Acrylic sheet 1/8"x2'x3'
  6. Nuts and bolts.

Step 2: The Display Box

We chose flipdot displays to ask the questions. These delicate and almost obsolete mechatronic devices are made in (and only in?!) Poland. We love them because:

  1. no power consumption unless they're changing
  2. very legible in direct sunlight as well as dim street light
  3. fun to stare at and listen to when they animate

If you buy them from alfazeta like us, remember to get a few extra flipdots. They fall off during shipping and handling. No big deal though! Put them right back on with a tweezer.

The flipdot displays and raspberry pi that drives them (details here are encapsulated in a plywood box with acrylic windows. I cut out 3/4" plywood panels on shopbot and glued them together with wood glue. Windows are covered with acrylic to protect them from dust and water, and poking fingers. Trust me, people do try to flip them by hand all the time, and it could be lethal to these fragile electronics.

Step 3: The Columns and the Sensors

The display box sits on three columns. As shown in the first image, each columns are made of

  1. four panels of plywood glued into a square pole
  2. two square metal tubes that fit inside the plywood pole, and secured with two 1/2"-13 bolts that drives through both.
  3. each metal tube has a square flange welded to its end, which is mounted to the display box and the base, respectively. Mark the edge where the metal tube and the flat piece meet, so it's easier to align when it comes to welding time.

The tricky part about the columns is the sensors. We use industrial polarized retroreflective photoelectric sensors, which work really well even in direct sunlight. (Thank you Robb for the suggestion!!) We want to hide these sensors inside the columns so they can't be easily poked, but we also want it to be easily adjustable since the cutting, welding, and installation all adds error, and the sensor and reflector may not line up correctly.

Out solution is to build a bendable mount (referring again to Robb's solution) on the steel tube. When installing, erect the steel tube, then sensors. Align the sensors, before sliding plywood pole onto the steel tube. The poles, as shown in the last image above, have holes pre-fabricated in them for the light to go through.

Material bill for the sensors

From (A fast and reliable resource!):

  • GXP-AN-1E X2 breakbeam sensor
  • CD12M-0B-050-A1 X2 cable that plugs into the breakbeam sensor
  • RL110-1 X2 matching reflector

From any supplier

  • Arduino to read the sensor
  • 10-30v power supply
  • Some resistors/ pot for dividing voltage

Step 4: The Base and Assembling

If you can bolt the columns to the floor, by all means! If you can't, calm down and bring your own floor! We BYOF'ed our 4'x8' sheet of 1/2" thick aluminum base, and bolted down the columns with 1/2"-13 steel bolts. It held up great when people tried to pole dance at 2am.

You'd need to

  1. Pre-drill 12 holes on the base, at exact locations where the flanges' through holes are. I used waterjet and it's beautifully precise. If you're drilling it by hand, make the through holes on flanges bigger to be safe.
  2. Thread these holes.
  3. Add a few through holes for 1/4" set screws. If your floor isn't flat, the edge of the base sheet might tilt up and that's dangerous! Use these set screws to bulge up the center and keep all edges down.
  4. Add slip-grip tapes on the base. We also spray-painted our logo onto them. The paints held well despite 10k steps and jumps and dances.

Step 5: After Thoughts

The whole time I was building the door, I was excited and nervous about one question: Would people vote?

The answer, as it turned out, was a definite YES! The crowd's response was tremendous. People voted. Friends laughed. Strangers talked. They took a moment, read the question, reflected on it, whether serious (death penalty) or silly (cats or dogs), reflective (are you happy) or evocative (Trump or Hitler), technical (vim or emacs) or whimsical(would you dance through the door?).

Better yet, all these questions come from the people. We are so proud of all of you who submitted these questions, either online or in person. It was your questions that gave the Vote With Your Feet a soul.

Thank you all who completed the projects with us!