PedalOn is a system intended for use by pianists who have difficulty using the sustain pedal of a piano and need an assistive mechanism. Rather than using the foot, this system allows the pianist to activate the sustain pedal with any simple switch they find easy and convenient to trigger. When the pianist triggers the switch, the system instantaneously responds to depress the pedal. The pedal is relased only when the pianist releases the switch.
Now in its second generation, PedalOn is designed to be completely open-source. The system is built primarily from easily obtainable, off-the-shelf components in order to make it as widely available and accessible as possible. Our goal, and the purpose of this website, is to pass on all the information required to build this system to anyone who could benefit from having one of their own. With a modest knowledge of electronics and mechanical assembly, PedalOn 2.0 should be straightforward to replicate.
PedalOn began as a student project in the Mechanical Engineering department at Stanford University. Four students--Jessica Chapman, Jean-Paul Labrosse, Jodie Prud'homme and Patricio Delgado--worked with Roger Cowger, a retired pianist who had lost the lower portion of both legs. The goal was to design for Roger a system that would allow him to actuate the sustain pedal of his piano using only the mobility and strength available in the remaining portion of his upper right leg. The completed system allowed Roger to play the piano again for the first time in years. Roger graciously gave a small performance, and the joy of seeing him use his new system was one of the greatest moments of the designers' academic careers.
In addition to the reward of seeing Roger reunited with his craft, the team also received both the Lincoln Arc Welding Foundation Award and the Stanford University Mechanical Engineering department's Fuchs Award in Design for their work.
After the completion of Roger's system in the Spring of 2001, the design team received occasional inquiries as people sought out information for systems of their own. Due to certain components used in the original design and the availability of the team members, the advice and help the team was able to provide was limited. Eventually, the team was contacted by Olivier, a French pianist who offered to sponsor a redesign if a system could be produced for him. Intrigued at the prospect of bringing new life to the project and of the potential to offer more assistance to others, the team discussed embarking on a complete redesign of PedalOn.
It was at this point that Pocobor was brought on board. Given the time-demanding nature of the project and the expertise in design and mechatronics that Pocobor could bring to the table, it was obvious the project stood to benefit a great deal from working together. Over the course of the following months, Pocobor charged ahead with re-evaluating and revamping the design, working from the ground up to produce an open-source, reliable and user-friendly device. Finally, in November of 2009 the second generation of PedalOn was produced and delivered to Olivier, who continues to happily use his system.
The main components of the PedalOn 2.0 system are the solenoid, the electro-magnet, the stand and base plate, the adjustable brace, and the electronics and software. All of these components reside in a single, freestanding unit which is placed beneath the piano key bed. It is positioned such that the push rod of the solenoid rests just above the sustain pedal when the solenoid is 'off'. Once properly positioned, the adjustable brace is tightened to brace the unit against the underside of the key bed and prevent wandering with use of the system.
The player's switch is connected to an input jack on the electronics enclosure at the base of the unit. The switch is used to signal the system whenever the player wishes to depress the sustain pedal. When the player activates the switch, the system receives this signal and turns the solenoid 'on'. When the solenoid is energized, the push rod extends with enough force and travel to depress the sustain pedal. Once this has occurred, the system's software automatically energizes the electromagnet. The electromagnet holds the push rod in place to keep the pedal depressed so that the solenoid can be turned 'off'. This is necessary to decrease the required duty cycle of the solenoid and prevent over-heating. When the player releases the switch, the software de-energizes the electromagnet, thus releasing the push rod and allowing the sustain pedal to return.
While the user is playing the piano, it is important that the PedalOn system operate quietly so as not to detract from the music. To this end, several components were included in order to reduce noise. The solenoid and the electromagnet cause rapid movements with large forces, which can be noisy. Furniture pads placed at the solenoid stop and a Teflon sheet placed between the electromagnet and the electromagnet plate counteract this noise production. In addition, the base plate of the unit is mounted on a felt pad and vibration-reducing rubber feet. The swivel foot at the end of the adjustable brace is also felt-padded.
PedalOn 2.0 was designed to be useful across a wide range of piano makes and models, which inevitably have varying geometries. Several design details were incorporated into the system to account for differences in key bed height, pedal height, pedal travel and pedal stiffness (in other words, the force required to move the pedal). The threaded rod of the adjustable brace, for example, can account for several inches in key bed height differences. The ability to adjust the stationary position of the solenoid by mounting it to a linear rail allows for variance in pedal height from the floor. To provide the proper amount of force to move a pedal on a given piano, a knob on the electronics enlosure allows the user to adjust the solenoid force and travel through software.
These and other details of the design are more fully explained in the design documentation available on the blueprints page.