Intellitec Multiplex Low Voltage Switching

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Technically Speaking:  Intellitec Multiplex Low Voltage Switching

When this slick new system debuted on Country Coach motorcoaches, Brian Keys, an electrical engineer then employed with the Engineering Dept at Country Coach Inc, shared a description of it in an easy to follow along style that was so trademark-Brian Keys. Here’s a condensed version of his info he shared about this system.

    In 2006, the former Country Coach LLC introduced a modular switching system to its 2007 model year Allure, Intrigue, Magna and Affiinity models that broke the traditional physical connection between the switch you press and the mechanical contacts that close behind it to activate an electrical circuit such as ceiling lights. The Multiplex Low Voltage Switching System by Intellitec allowed two functions of a traditional switch to be separated by a communication harness allowing the freedom of choice in where each should be located in the coach.

    An example Brian Keys, then CC, LLC Electrical Engineer, used in 2006 when describing the new system was to illustrate the system’s functionality through an explanation of the water pump circuit. He described how it has evolved through the years. “The water pump circuit is a simple circuit but one that typifies the limitations of a traditional switched circuit. Not too long ago, the typical Country Coach would only include a single rocker switch in the bathroom to turn the water pump on and off. The switch’s location in the bathroom was entirely logical but it was also in close proximity to the water pump itself and the fuse panel from which it was powered so the wiring to and from the switch was relatively short. The circuit was simple, comprising a single fuse, two lengths of wire, the switch, and the water pump itself.”

    “As the circuit evolved, a second water pump switch was added in the front coach area so you could turn off the water pump as you walked out the door. A simple addition, but it presents some immediate challenges. In order for the switch to work, it needs wires, but not just two wires as you might expect. To ensure that the water pump could be turned off from either switch, a traditional two switch circuit actually requires a total of four wires. The light on the switch that illuminates when the pump is running would need another two bringing the total to six wires, many of which have to be routed all the way to the front of the coach and back. The simple addition of a second switch had an impact on the circuit’s harness requirements and the additional weight that comes from the running copper wires to remote locations for a switch is not insignificant. An alternative design used by CC is to use a basic electronic circuit board to control the pump and simplify the wiring to each of the two switches. More often than not, the electronics bring simplification to a circuit rather than complexity, even a circuit as simple as that used to control a water pump.”

    Simplification. Brian Keys went on to explain: “So, why limit a control board to a single circuit such as the water pump when it can be used to control multiple circuits in its general area? What if multiple control boards were used through the coach to directly control circuits in their immediate area, eliminating long harness runs to and from a switch? This is the operating principal behind the Multiplex Switching System. Staying with the example, the current circuit simply involves any number of water pump switches through the coach which when pressed, sends out a signal on the communication harness to the Intellitec PMC (programmable multiplex controller). The controller in turn sends a message on the communication harness that is addressed to a specific module and output. The module receives the message and turns on the output to supply power to the water pump. This module is mounted in close proximity to the water pump and up to ten other circuits thus eliminating long harness runs.”

    “Want to add the water pump switch to another panel? Simply change the address of the new switch to match the address of an existing water pump switch, an operation that can be done in minutes rather than two or three hours of labor it might take to route wires to a hard-wired switch. Want to add an accessor to the coach? Wire the accessory to an output module in close proximity that has a spare output. Then locate an unused switch and have its address programmed to match that of the output on the module that your accessory is wired to and the job is complete. If there is no module closed by then one can easily be added.  The same is true with switch panels. One of the big advantages with this system is Flexibility. Another advantage is the reduction of overall harness weight which is approximately 30% for the Magna and Affinity coaches. All switch panels are backlit for easy nighttime operation and the backlighting can be turned on or off with a momentary press of the “All Off” button. Holding same button down for 4 seconds will power down the entire system. On Magnas & Affinitys the Fresh Water Drain switch must also be held down for 4 seconds to drain your fresh water tank.”

    “When it comes to ceiling lights, many of these are dimmable simply by holding down the respective switch to cycle through the brightness levels to the preferred brightness. To turn lights off, give the switch a momentary press and turn them on again in the same manner. The lights will turn on to the same brightness level that they were previously set to when turned off. All other switches operate like a regular switch; press to turn on and press again to turn off.”

     Blown Fuse? The fuses for Intellitec switched circuits can be found on the modules. Magna/Affinity modules are behind passenger side map box; beneath galley sink; in rear overhead cabinet; above bed in forward overhead cabinet; in cabinet on passenger side of wardrobe; and in electrical bay. Intrigues are located above driver’s seat in overhead cabinet; in rear living room overhead cabinet; bottom rear of dinette wall module; above bed in forward owverhead cabinet; in cabinet on passenger side of wardrobe; and in electrical bay.

Intellitec Modules commonly used on Allure through Affinity models are:
PMC-Programmable Multiplex Control:The Brains. Maintains network integrity;  maps keypad buttons to correct module outputs.

10 Channel FET Output Module- Powers up to 10 dimmable circuits such as ceiling lights.

10 Channel Relay Output Module- Powers up to 10 regular on/off circuits such as water pump.

6 Channel Relay Output Module/4 Channel Input Module- Powers up to 6 regular on/off circuits and accepts input from up to 4 non Intellitec switches.

10 Channel Input Module- Accepts input from up to 10 non Intellitec systems

Quad H Bridge- Primarily used to control up to 4 reversible DC motors but can also be used for regular on/off circuits

    Brian noted that “All modules include a two or three-wire communication harness. A red LED below the harness connector illuminates if there’s a communication failure, and a green LED above or below each module output illuminates when output is turned on. All modules use commonly available MATE-N-LOG connectors and Country Coach mainly uses a later generation of this connector that can be easily disassembled for servicing without tools.

    Reliability. “Intellitec has a decades-long reputation for mature, stable design. The communication harness is immune to external electrical noise that is always present inside a motorhome (due to the high number of low and high voltage systems confined in a small space). The dimmable outputs are surprisingly quiet (electrically speaking) so shouldn’t cause significant interference with radio reception. As with any electronics, the Intellitec system may start operating erratically if the domestic batteries become severely discharged. The system will typically revert to normal operation once the batteries start receiving a charge but if not, simply reboot the system by turning off the domestic battery disconnect switch and turn it back on after a minute has passed.”

  Further information on this topic can be found at http://intellitec.com

 Intellitec has been designing and manufacturing multiplexed solutions for the special vehicle market since 1987, these products and systems range from simple multi point switching controllers through to complete vehicle systems used in Buses, Coaches and Emergency Service vehicles worldwide. Programmable Multiplex Control (PMC) has 320 channels of I/O across a very significant family of I/O hardware architecture to suit the majority of applications. PMC operates with one master module (CPU) with various I/O. Each I/O module has ten channels, you can have as little as 1 I/O module in a system, or as many as 32. The Intellitec Windows based PMC software suite WIN PMC is used to configure the system, only the master or CPU requires programming. Win PMC is a series of AND, NOT & OR commands, coupled with timers and 160 virtual channels make this an extremely powerful tool. For full and detailed technical data, please download our PMC Catalog at http://intellitec.com/