GUEST POST:
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.
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/
