Fineline Solutions was approached by the production company responsible for The Voice of Ireland to build four rotating bases for the judges’ chairs. The concept of the show requires the judges to initially face the audience while the contestant performs their piece. If the judge likes what they hear, then they press a button on the arm of the chair and the chair rotates to face the contestant. A remote button panel allows a technician to rotate the chairs manually in either direction, or to rotate all chairs simultaneously. A DMX output is used to control lighting on the main rig, for instance adding lighting to illuminate the judge’s face.
The second part of the brief is to use the same rotating bases as part of the live shows, which occur later in the season. The set for the live shows employs four large video screens, which can be rotated to make entrances for hosts, contestants and dancers.
The rotation bases needed to be robust, and needed to be able to move to a pre-defined position with repeatable accuracy. In addition, the bases needed to be able to move together, i.e. starting to move at the same time, and finishing the move at the same time. The system was to be powered from a single 16A power supply.
Each base consists of a welded steel frame, which was manufactured by Fineline Manufacturing. The frame supports a large slew ring bearing, which is used to support either a chair or a video screen. The bearing and base were sized to ensure that there was no possibility of the chair or screen toppling when in use.
One additional constraint was to ensure that the height of the base was kept to a minimum. This presented some challenges when mounting other equipment: it was necessary to choose a motor and gearbox combination to provide the requisite torque, but also to fit within the confines of the base.
Each base was equipped with a standard three-phase AC motor, which was connected to the slew ring through a gearbox and appropriately sized drive gear. A variable-frequency drive (VFD) was used to drive the motor, allowing the speed to be varied and also allowing torque to be maximised at low speeds. The VFD required a single-phase mains input, and standard analogue control input. Finally, a shaft encoder was attached to the motor shaft, allowing the position to be ascertained with a high degree of accuracy, even when the power is removed.
Each rotation base was also equipped with a terminal strip, allowing the button on the arm of the chair to be read by the controller. An umbilical connects each base to the central controller, and contains mains power for the VFD, and the various low-voltage control signals.
The system consists of a single central controller, which manages all four bases. The controller is provided with a single 16A power feed, and this is supplied to each of the four bases via the umbilical cable. The controller makes use of an industry-standard programmable logic controller (PLC), which is able to read digital inputs, set digital outputs, read shaft encoders and produce the analogue control signal used to control the VFDs.
The controller itself is responsible for determining how a particular move should take place. For instance, the chairs start at 0° (i.e. facing the audience) and turn to 180° when the judge presses the button. The controller determines the movement profile, i.e. how fast to accelerate, how long to move for, and how fast to decelerate. The system was tuned on site to provide the best compromise between smoothness of movement, speed of movement and positional accuracy.
Although the judge is responsible for pressing the button to turn the chair, a technician is provided with a button panel to allow each chair to be turned, or reset to face the audience. The panel also provides an ‘all turn’ and ‘all turn back’ button to allow all chairs to be turned at the same time. The controller ensures that the move starts and finishes at exactly the same time.
When the system is used to rotate video screens, the controller acts in a very similar fashion, and is still responsible for ensuring that the movements are coordinated correctly. The button panel is used to provide nine preset positions, and the operator can select these positions as required by the production. A dead man’s handle button is provided, which allows the operator to stop movement immediately should a problem occur. The reason for this is simple: the clearance between adjacent screens is fairly small; clearly it is necessary to stop any movement quickly if someone accidentally walks between the screens during a move.
For further information, or to discuss a similar project, please contact Fineline Solutions.