Alpha microcontrollers control air conditioning units

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Clim Cool Project has used seven Mitsubishi Alpha XL microcontrollers to monitor and control the air conditioning system in a mobile television broadcasting centre.

Alpha microcontrollers control air conditioning unitsMitsubishi Alpha microcontrollers are helping to ensure reliable global TV coverage of major events, such as sporting festivals, by controlling the air conditioning in the mobile broadcasting centre so that both staff and equipment function at maximum efficiency.

Clim Cool Project of Renningen, Germany, developed the air conditioning system for the television outside broadcast unit used throughout Germany and further afield. Packed with the very latest technology installed by BFE Studio und Medien GmbH, the truck is one of the most advanced outside broadcast units, supporting up to 28 TV cameras and equipped for high-definition digital television (HDTV). In addition to the equipment, it has space for around 18 staff, including audio technicians, video operators and broadcasting directors, all of whom work in the trailer during the broadcasts.

70kW of heating and cooling

Clim Cool fitted the trailer with a 70kW air conditioning system for cooling, heating, ventilation and dehumidification. It is designed to be equally able to cope with ambient conditions at snow sports events or summer broadcasts from southern regions. While the staff can adjust the temperature of their workroom between 18 and 28degC, the temperature of the air fed into the electronic equipment is automatically maintained at a level between 10 and 18degC. The temperature must be neither too low - because this could cause condensation and shorts on the electronic circuit boards - nor too high - which could result in defects caused by overheating. When the outside temperature is below 10degC, the system first switches into heating mode until the temperature sensors register 18degC, then the heating is cut out and the equipment is cooled. When the outdoor temperature is above 10degC, cooling mode is activated immediately.

The air conditioning has a total of eleven heat exchangers (one for each cooling station) and seven compressor units. Space inside the trailer must be used as efficiently as possible, so the air conditioning components must also all be small, powerful, reliable and quiet enough not to interfere with the broadcast.

Seven controllers

Seven Mitsubishi Alpha XL microcontrollers monitor and control the entire air conditioning system using two-point control. The engineers at Clim Cool Project choose the Alpha XL because each unit supports up to 28 I/O points, including eight analogue inputs. These are needed to connect temperature sensors and setpoint generators for each cooling station and two pressure transmitters for each compressor. The outdoor temperature is measured with an additional sensor, the values from which are daisy-chained through to all the controllers.

There were a number of other criteria that influenced the controller choice: to begin with, the Alpha XL is specified for operation in an ambient temperature range from -25 to +55degC, which was very important for the wide range of conditions that the outside broadcast unit is to be used in. The engineers also wanted to distribute the air conditioning control tasks across several smaller controllers to increase overall reliability.

Another big advantage is that all the open- and closed-loop control processes are run within the Alphas, which helps to keep the wiring and the number of terminals to a minimum.

The Alpha XL microcontroller closes the gap between individual components - like relays and time switches - and a full PLC. It delivers a high level of functionality, reliability and flexibility at a very reasonable price. The Alpha can process up to 200 function blocks in a single program and each function (time switches, counters, analogue signal processing, clock/calendar function, etc) can be used as often as required by all programs.

Clim has a track record of similar projects dating back ten years or more, including a Formula 1 team's VIP paddock tent.

19 March 2007

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