By Chris Roche, STEM Faculty

The Circuit Engineering Stair Master

The students in my spring “Robotics and Circuits Engineering with Physical Computing” class did it. They pulled it off!! We now have the “Stair Master” currently installed and running in the stairwell off the first floor of the St. Mark’s STEM building. Students and faculty like the installation, and we are looking forward to a phase two expansion that has music!

The “Stair Master” is an installation that allows a flight of stairs to be interactive with the people walking on them. Here are videos showing the Stair Master in action:
Video 1: Click Here
Video 2: Click Here
Video 3: Click Here

When you step on one of the steps in the “Stair Master”, LED light strips light on the stair you are on. The system uses sensors to know which stair you are on, triggering the appropriate lights. There are versions of interactive stairs already existing, such as the musical staircase at the Museum of Science in Boston. However, the “Stair Master” at St. Mark’s was designed and prototyped exclusively by the “Robots and Circuits” class, using class-built knowhow and our prototyping process. “Robotics and Circuits Engineering with Physical Computing” is a “Maker” elective at St. Mark’s which teaches students DIY electronics, building and programming. The Maker Movement burst onto the national culture and schools about a decade ago.

As a teacher, I love the educational value I get with students by “dreaming big” and realizing their dream. This is one important aspect of the “Robotics and Circuits” class, where anything can be possible with some planning and electronics/programming knowhow. In this class, students first learn basic rules like Ohm’s Law and the Kirchhoff current and voltage rules. These rules allow us to make simple circuits like series circuits, parallel circuits, and voltages dividers. To make all of our circuits, we use simple electronics parts and on-line prototyping systems like Autodesk Circuits. As a group, every time the class begins, we pick a final project. In one year, the class built radio controlled blimps. In another year, the class built persistence of vision (POV) devices.

This year, the class wanted to build the “Stair Master”. In order to build the “Stair Master”, we started out with some preliminary research. On Canvas, with our school’s Learning Management System (LMS), I set up a discussion and asked all of the students to contribute ideas on how to build the Stair Master and what components were needed. Some of the ideas needed to be resolved or needed to be seen as feasible (both in terms of complexity and cost) right away so we could potentially complete that project. One thing we needed to prove was that we would be capable of wiring a large number of LEDS, which run at a relatively high voltage of 12V. We don’t usually work with a number as high as 12V, making this serious for our group. Above all, we needed to show ourselves that we could do the wiring in a safe way, and also we needed to control the 12V using our chosen computer device (the Arduino) which outputs at only 5V.

After our preliminary research, we then went on to a phase that prototyped our project using an online tool called Autodesk Circuits. Though this program didn’t have the same LED light strips we used for prototyping, we could substitute in the circuit another 12V load, such as a motor. This tested the feasibility of our wiring and look at current draws:

From there, when we knew our setup would work, I printed out large cutouts of all of our components and asked the students to create wiring diagrams on paper (using paper cutouts of all of our actual components).

From our prototype setup, the basic components are:

1) An Arduino, a microcontroller board which open-source software, used by many makers in DIY Project:

2) LED Light Strips, which can be cut to the size of the step (we used two strips on each stair).

3) N-MOSFET Transistors, which act as switches and allowed us to control 12V lights using a 5V gate switch. With more voltage applied at the gate by the Arduino, more 12V current goes through the transistors to light the lights.

4) An Infrared range finder senses when a person was on one of our steps. We used this to trigger the lighting of the lights.

5) A power supply provides the amount of amps (amperes) that we needed for our number of lights.

With those basic supplies we went to work, each student built one or more stair set up for the Stair Master. There is an LED triggering “set up” on each of the stairs. Here are images from the build:

We also tested each unit before it could be used on the stairs:

After further testing, we found that we had a bit of a flickering problem. By using some resistors and making sure the “gate” on the transistor was grounded and not “floating”, we would then get great performance. Our final wiring looks like this:

…close up of breadboard:

As a final project in class, we installed the units to the stairs and added posters to explain our project. That is currently in the stairway in our STEM Building now, but this is only phase one. We are working to incorporate sound to the project using a serial to MIDI interface and a MIDI sampler program (like Kontakt 5):

And we plan to add that sound to feature to our “Stair Master” in Phase Two with volunteers from this Spring’s class. In a permanent installation, we would further migrate parts to all of the breadboard to a soldered circuit board, taking the temporary breadboards away.

“Stair Master” has been a fun and interactive project. We learned a lot about electronics and showed how it’s possible to build something the whole community can appreciate with some simple research and DIY knowhow!