The goal of this project was to make a portable musical staircase system that could be temporarily installed on a staircase in “Dekalim” school, for musical therapy sessions with autistic children.
We decided to build a wooden frame around each step, at the end of which there is a laser source on one side, and a photosensor on the other side.
The Arduino Leonardo sends key press commands to the laptop via the USB (this method was inspired by the MakeyMakey). The laptop runs an user configurable free sampler program that can be found here (This is the initial reason for building this website). The sampler responds to the key press events and plays sounds.
Click Here for an example of the system at work (my daughter was our test subject, but I could not resist and joined her)
For this version of the stairs we used photosensors that come with a built in digital output and a sensitivity potentiometer. This allowed for simple programming of the Arduino.
The tricky part is aligning the laser and the photosensor. The length of the stairs is about 175cm, so a laser misalignment of one degree results in a deviation of 3cm on the sensor side.
Both components are attached to an L shaped bar. One screw connects the sensor to the L bar, and another screw connects the bar to the wood frame, allowing for rotation of the sensor on two axes.
In order to connect the laser source to its L bar, we hacked a cable clip. The nail of the cable clip was replaced with a screw.
The Arduino Leonardo compatible board (from www.elecfreaks.com) is a bit tricky. In order to program it you have to push it’s reset button, while the button is pressed initiate the upload in the Arduino software. Release the reset button only after the Arduino software status bar says “Uploading”.
We bought the components at Deal Extreme, the home for cheap electronics (danger: this site is addictive).
The guys and gals at IDEO used IR distance measurement components instead of the lasers. The downsides of the IR components are price and the beam width which according to the discussion in the Sparkfun site is about 3 degrees. This is a good choice for short stairs, but for longer stairs the beam width could pose a problem.
Pressure sensors can also be used, but I did not find cheap long reliable pressure pads (if you find any, please let me know). I am working on a version of homemade pressure pads, I will post the results of this work another time.
Pros and cons:
Pros: The system is cheap, easy to build, and works great if setup properly (Aligning the components and setting the photosensor sensitivity).
Cons: The system is not sufficiently durable. Whenever the stairs are removed to storage and then returned to the staircase, setup is required again. We are working on a more durable version… more on this in a later post.