As part of Channel 4’s 25th anniversary year, a 50ft high metal ‘4’ was constructed outside Channel 4’s premises in London. It has played host to a number of art installations as part of the Big Art Project. As part of this project, a number of artists have been given chance to create ‘skins’ for the structure. One of these was called Time to Breath, and was designed by Hannah Gourlay. The design involved covering each section of the ‘4’ with fabric, and making it breathe gently, swelling as the structure ‘inhaled’. At night, the ‘4’ was to be lit from within.
Fineline Solutions was approached to write software to control the inflation and the lighting, using an industry-standard PLC platform. The software requirements were as follows:
- Construct an algorithm to make the structure slowly inflate and deflate, mimicking a breathing action as closely as possible
- Implement a celestial clock to determine when the interior lighting should be turned on and off, matching dusk and dawn times
- Using the same celestial clock, activate and deactivate the fans at the appropriate times of day to comply with noise pollution requirements
The controller was based around a Wago PLC, with several I/O modules: analogue 0 – 10V output, analogue 1-10V input, digital 24V logic outputs, a relay module and a DALI module. The ‘4’ logo itself consisted of a number of segments, each of which had a separate fan and pressure sensor attached. Inside each segment were a number of DALI-connected dimmable fluorescent tubes.
A PID loop was implemented for each segment, allowing the controller to ramp the fan speed up and down in order to achieve the desired pressure. The fans were controlled using standard industrial Variable Frequency Drives (VFDs) controlled via the 0 – 10V analogue interface.
The target pressure was continuously varied using a simple sine wave function, setting the pressure for all cells globally. The larger cells were equipped with larger fans, and the independent PID loops ensured that the peak inflation was reached at the same time.
One of the requirements was to turn on the interior illumination at dusk, and switch it off at dawn. As the dusk and dawn times vary each day, it was necessary to implement a celestial clock algorithm to determine when to turn the lighting on and off. A simple relay was used to turn the lighting power on and off, and the DALI interface was used to adjust the brightness to match the breathing effect – getting brighter as the ‘4’ inflated.
While on site, it was necessary to ensure that the fan noise did not exceed agreed noise levels, as the ‘4’ is situated in a residential area. By varying the target pressure and PID loop parameters, it was possible to reduce the fan noise to an acceptable level. In addition, the fans were shut off entirely during the evening and night.
For further information, or to discuss a similar project, please contact Fineline Solutions.