Multiplexing

**rualfire** · 02-07-2006, 04:29 PM

Is there someone out there who can explain the multiplexing concept to me? We haven't got a multiplexed rig, but the time will come...

I've inferred from the reading I've done that it is a common 'bus' for power on the rig. Is it that simple? A thick + wire that everything is tapped into?

Or is there more to it?

Saw an ad recently in FH mag for a hydraulic multiplex generator.... (??? WTF ??? )

Thanks for your explainations. Please use small words.

Randy

**jake2415** · 02-07-2006, 04:37 PM

Bare bones of the systems I am familiar with is this:

Standard wiring systems use a wire for every light, switch, and electrical device. Multiplexing consists of one wire carrying mutliple signals to provide power to multiple devices, thus reducing the number of wires in a truck. Also when a truck is multiplexed it can be easier to determine electrical problems. Everything is customizable on a multiplexed rig. I know there are going to be people on here who say that multiplexing is a horrible thing and that it makes the trucks too complex, let them have there opinions. Personally I would reccomend the Class One system, it has been around for a few years and most of the bugs are worked out. If used right and used on a single source truck (manufacturer makes the cab and chassis themselves) it can be a great system. Just my 2 cents

**toddmcbr** · 02-07-2006, 07:44 PM

Multiplexing is becoming very popular on trucks and eventually will be the norm. Like Jake said, it is very customizable and the options of what you want to do with it are pretty much endless.

With multiplexing, the truck is split up into different nodes which are located throughout the chassis and the body. All the different devices hook to a node and there is a cable that runs from the node to the brains. So instead of running a different wire for each warning light to the master switch panel, they are hooked into a pin on the node. If there are emercency lights hooked to pins 1, 2, 3 on node 8 - - Pins 1, 2, 3 on node 8 are activated when the the operator turns on the Mater Warning Light button the control panel. The system is very scalable so you could do quite a bit with it.

I have seen both the Class 1 and the Weldon. I personally like the Weldon system. It is very easy to use with a nice color screen which can be used for up to 3 video inputs such as side and rear cameras.

Single source has nothing to do with this. Spartan uses Weldon and when the body manufactuer starts building on the truck, all they do is add on to the system by adding nodes, connect the wires and program the system.

**EWFAC1075** · 02-07-2006, 08:01 PM

I'm not a big fan of multiplexing for one simple reason; a problem usually results in a catastrophic failure. We encourage our clients to avoid it.

East West Fire Apparatus Consultants Inc.
Apparatus Design Specialists
866-843-1075
www.ewfac.com

**HFD147** · 02-07-2006, 10:54 PM

Well, here we go. This last comment just reinforces my theory that consultants are people who collect a fee from someone else in order to share their opinions, whether fact-based or not.

In this case, quite the opposite is true....multiplexing ACTUALLY makes a problem easier to diagnose and rectify. Got a phone in your house or business? Well, its multiplexed. When's the last time it didn't work? Catastrophic failure due to the fact its multiplexed? Show me case history...then I'll give your statement some merit.

Major emergency vehicle manufacturers are using multiplexing and it works quite well. Remember, Freightliner, International and many other truck manufacturers use it in HUNDREDS of THOUSANDS of vehicles because its STATE-OF-THE-ART technology. If its good enough for the operators driving thousands of miles a year, it oughtta be good enough for us.

Advising your customers to stay away from it? Must be you have stock in horse-and-buggy companies. Otherwise, your fact-devoid advise is deprivivg your "clients" of the latest development in electrical system technology.

Why do some Fire Service "consultants" see the need to buck advancements when they exist for their clients own good? Please give the intelligent consumers in our field some credit.

**aerialguy1** · 02-08-2006, 02:31 AM

The advent of Multi-Plexing has been around for a number of years and was initially used in the Transit Coach business. Yes there have been problems with probably ALL of them at one time or another BUT these can be quickly corrected and resolved easier than the old style way of having to trace wires or "wonder" where the problem is.

I can speak for using the Weldon system (now owned by Akron Brass) and it's in service with a number of FD's both large and small throughout North America. (Dallas, Fort Worth, Charlotte, Riverside County CA (50+) Edmonton and Calgary in Canada and I've talked to the mechanics who've worked on them and they said they wouldn't go back to the old style system.

Spartan looked long and hard at both systems and went with the Weldon ilo of Class 1 and ALF now offers the Weldon and Pierce have their own which is proprietary to them and it's a Master Slave verses the Weldon which is a Peer to Peer.

The major issue is to ensure the builder your looking at "has" experience with them in having built and delivered a number of trucks. The features and advantages far outweigh the disadvantages IMHO and you can reprogram it to make changes to controls etc.

The Weldon V-MUX color display is great too as you can incorporate a backup and RH side view camera as well as a easier control of all the switches compared to the conventional style. Finally the old problem of the "Door Ajar" light and which door is ajar is easier to identify because the builder can show a schematic of the apparatus and indicate which door is ajar at a glance.

Finally the car and truck manufacturers are using multiplexing so it's only a matter of time so better to be the flow and although there are sometimes a problem they can be easily solved IF the builder has the knowledgeable people to assist a FD mechanic in a situation.

**rualfire** · 02-08-2006, 09:21 AM

Originally Posted by toddmcbr

With multiplexing, the truck is split up into different nodes which are located throughout the chassis and the body. All the different devices hook to a node and there is a cable that runs from the node to the brains. So instead of running a different wire for each warning light to the master switch panel, they are hooked into a pin on the node. If there are emercency lights hooked to pins 1, 2, 3 on node 8 - - Pins 1, 2, 3 on node 8 are activated when the the operator turns on the Mater Warning Light button the control panel. The system is very scalable so you could do quite a bit with it.

I want to be sure I understand this correctly.

Power +12v is run out to a node.
A node has serveral 'channels' it can turn on and off
A node would listen to a central processor for control signals, and provide feeback about the status of each 'channel'

Correct?

Also, what is the signaling mechanism between the controller and the nodes? A digital signal I would assume?

Also, thanks for the insight regarding your experience with the multiplexed systems.

Randy

**Rescue101** · 02-08-2006, 10:16 AM

My opinions on multiplexing are pretty well known.Horse and buggy days? Well,I don't want to go back that far,but I never had a rig with a mechanical connection between the throttle and the fuel control fail.Can't say the same about the electronic ones.Same with multiplexing.After it's been in ACTIVE fire service across the board for 10 or so years(withou problems),I'll get a little more excited about it.Easier to repair? Ah,yes and no.Simple programming,module issues may be easier but other issues will be like any other computer with a problem,intermittant and HARD to find.For me,I still don't have a problem with a piece of wire,pretty easy to find and repair faults here.But I remain open to 'plexing,once the "bugs" are worked out. T.C.

**lvwrench** · 02-08-2006, 06:23 PM

As those for the multiplex system have said; if it is correctly installed it is the greatest thing since sliced bread. Well, unless the manufacturers have developed some intelligent installers along the way I'm not totally convinced. Problems with units dying, you bet and at the worst possible times. LED screens that are obliterated because they did not account for the 110-120 degree sunlight for the Southwest. Over the road truckers and cars for the public are fine because they are not cobbled into by the after market people cobbling up the wiring. As for custom builders of chassis up makers they have their share of glitches too. Circuit boards, computers, relays, relay and circuit breaker panels, and anything else they can subject to water, vibration and the endless other things that can deteriate or come undone are the problems I see. Diagnostics through a long, very long phone cable with a lap top to talk to the factory, expensive diagnostic discs from the factories, yada, yada and so forth. We even had one guy at work that bought a brand new car that totally died at 300 miles due to multiplexing. They could not figure it out at the dealer so gave him another car. Yeh, great. I would not say that the diagnostics are all that great either. When technology becomes bullit proof I'll buy it. My personal vehicle is a 73 Ford truck with no computers and it gives me far less trouble than the wifes 2004 van.

**EWFAC1075** · 02-08-2006, 07:10 PM

Originally Posted by HFD147

Well, here we go. This last comment just reinforces my theory that consultants are people who collect a fee from someone else in order to share their opinions, whether fact-based or not.

In this case, quite the opposite is true....multiplexing ACTUALLY makes a problem easier to diagnose and rectify. Got a phone in your house or business? Well, its multiplexed. When's the last time it didn't work? Catastrophic failure due to the fact its multiplexed? Show me case history...then I'll give your statement some merit.

Major emergency vehicle manufacturers are using multiplexing and it works quite well. Remember, Freightliner, International and many other truck manufacturers use it in HUNDREDS of THOUSANDS of vehicles because its STATE-OF-THE-ART technology. If its good enough for the operators driving thousands of miles a year, it oughtta be good enough for us.

Advising your customers to stay away from it? Must be you have stock in horse-and-buggy companies. Otherwise, your fact-devoid advise is deprivivg your "clients" of the latest development in electrical system technology.

Why do some Fire Service "consultants" see the need to buck advancements when they exist for their clients own good? Please give the intelligent consumers in our field some credit.

Well, seems as though we've hit a nerve. No, we don't have "stock" in any horse and buggy companies. What we do have is "many" years of experience in designing apparatus and many satisfied clients. If a client wants multiplexing in their apparatus then they will have it. If they ask us our advice, we advise them that we're not totally comfortable with the technology just yet, and let them decide. We do not strong arm our clients into what they choose. True, multiplexing has improved since it's inception. However, there are still issues that we have seen that should be considered. To compare over-the-road trucks to fire apparatus as an example just proves your inexperience. Finally, we are advocates of new technology. We do seminars on "Looking to the Future" when specifying new apparatus. The Telma retarder is a huge acheivement over the Jake Brake. So, I'm sorry your so upset by what we said about multiplexing. It still is our professional opinion that it needs improvement. If your not in agreement then thats your option and you need not "pay us a fee".

**bstiles** · 02-09-2006, 06:12 AM

Im an ASE certified mechanic for the Ohio Dept. of Transportation, we have several multiplexed vehicles(Intl. dump trucks). I as a mechanic feel that multiplexing is good from a service stand point, however there also many negatives to it as well.
The drawbacks to mulltiplexing are, you have to have a special scan tool in order to troubleshoot any electrical trouble, no more simplie test light checkouts, but the computer tool does save time and many headaches!!! The other problem I have encountered is, when you build a chassis, you have to spec. exactly what elect. items will be used on the truck; strobes, radios, defrost fans, etc. Which is a real pain, no room for expansion without alot of $$money$$(new computer).
All in all though I feel that it is very beneficial to upgrade when you purchase a new truck, keyword in that statement was I, you need to talk to your local servcice center and see what they say, I feel it benefits the service dept. the most.

**RetJaxFF** · 02-09-2006, 07:16 AM

How many times over our lives have we heard that a new technology was going to be the downfall of the Nation if not the whole Universe? The only part of new technology that bothers most people is the "NEW" part. Yes it means that the vehicle operators, and Techs have to learn "new" skills, and buy "new" tools, and of course "new" usually cost more. As time goes by the "new" wears off and what was once new technology will eventually be the norm.

If a fighter jet can "fly by wire" at the speed of sound I can't imagine why a Fire Truck can't operate by it. The technology is fairly new to the Fire industry, and it will simply take some getting used to.

Take care, and be SAFE.

**FF4020** · 02-09-2006, 08:01 AM

Ask any military jet crew chief how many hours of maintainence is required for every hour of flight and you might be suprised. Just because something is new doesn't mean you should use it! I think your situation and your truck will dictate what type of electrical system you should have.

Simple truck = standard wiring
Complicated tuck = might consider multiplexing
Dedicated maintainence staff = better chance of success with multiplexing
Limited maintainence staff = probably should stay with standard wiring

People bitch why trucks cost so much; yet turn around and load them down with a bunch of crap that has nothing to do with getting the job done.

Smaller departments need a rock solid truck that will give them many (30+) years of service. Multiplexing a tanker or brushtruck is about the dumbest thing I've heard off people doing.

**tomsome1** · 02-09-2006, 01:40 PM

Compare Body Builder Warranties Multiplex Vs Hardwire there is usually a bid difference also compare exceptions and whats covered in the warranties

**rualfire** · 02-09-2006, 01:59 PM

Thanks All for your input.

Just for the record. I'm not in the market to buy a new truck.

Is there a training document available online somewhere which outlines operations of the systems? I think I've got a pretty good grasp of the concept, I would like to understand the 1's and 0's of the implementation a bit. ( I work as a network engineer in my day job )

Any of you wrenches out there have refference docs online you can share?

Randy

**donethat** · 02-09-2006, 02:16 PM

If you go to class1.com

Under manuals, pull up the manual on the ES-KEY/USM Network. It tells you about everything you want to know.

A little to dry of reading for my taste.

**rualfire** · 02-09-2006, 02:30 PM

Bingo. Just what I was looking for.

The key was finding about about the communication protocol, and the types of control boards. relay and solid state.

Thanks much. I'll go away and chew on this for a while.

The Class1 ES-Key TM System consists of several components that can be used in a vehicle
electrical system. The system is multiplexed using the Controller Area Network bus and the
SAE J-1939 protocol. An electrical database is used by the Control Module to operate the
vehicle electrical system. The ES-Key TM Express software allows you to create, read or modify
this database. Troubleshooting of the system is also accomplished with the software.
The Controller Area Network (CAN) has specific requirements that should be met for
maximum reliability.
Network modules communicate with each other through the J-1939 Controller Area Network.
Network

There can be up to 16 Power Distribution Modules (PDM) in a system. The PDM’s control the
loads in a circuit. They come in two basic types, electromechanical (relay boards) and electronic
(solid state). They can handle from 7.5 amps up to 40 amps dependent on the exact
module specified. One of these modules is configured as an 8 input, 8 output, 4 motor driver
(H-bridge). A low current (250 mA) 16 Output Module is available for use in indicator or driver
circuits. The 16 output module comes in a variety of lowside and highside driver configurations.
(Power or Ground outputs)
There can also be up to 16 Switch Input Modules (SIM) in a system. These come in either 16
positive input or 16 polarity selectable input versions. Any switch or input in the system needs
to be tied to an input circuit on a module in the system.
Vocation Modules are available for interlocking and engine control tasks. These are enginetransmission
specific and there can only be one in a system.
A data logger is available that stores system fault and interlock information. It can aso be
configured to log specified circuit information. It will store 200 system faults and 6,000 events
before it loops around and overwrites the oldest data. These events are all dated and time
stamped to the nearest second. Up to 32 circuits can be tied to the data logger for troubleshooting
or information purposes. It is also a true time clock and a temperature sensor can
be wired into it. The time is displayed on the data logger. The temperature and time are
displayed on the Display Module.
There are variations of some of the above modules available.

**HFD147** · 02-09-2006, 08:59 PM

EWFAC1075: First off, you didn't hit a nerve. Those that know me also know that I will challenge anyone who uses a "business" to exert opinions without facts. That's all I meant in my response to your post.

Secondly, to clarify further: I have been associated with the Fire Service for 35 years, doing everything from grunt firefighter to apparatus mechanic to officer to training officer, blah, blah, blah. I have also worked on dozens of truck committees. So my comparison to over-the-road truck's multiplexing systems was certainly not based on "inexperience", thank you. You however have not presented any evidence to support your OPINION that fire apparatus multiplexing isn't within your comfort zone. Why? If you advised some customers to go with it, and then they had problems, then I could see your not being too willing to advise someone to get it. Is that the case? Or are you just not understanding the technology? Lots of things are multiplexed today, and the manufacturers are constantly striving to improve on what they have developed.

So, bottom line is: I don't agree with your advising "clients" against it, and that's based on my knowledge of the technology, not my opinion.

I would only ask, when you advise against multiplexing, what do you use for documentation to support that position? Sooner or later, you'll run into an educated consumer who will ask just that and back you into a corner......

**RetJaxFF** · 02-10-2006, 06:59 AM

Firehouse.com article

http://cms.firehouse.com/content/art...Id=13&id=47390

**EWFAC1075** · 02-10-2006, 12:21 PM

Originally Posted by HFD147

EWFAC1075: First off, you didn't hit a nerve. Those that know me also know that I will challenge anyone who uses a "business" to exert opinions without facts. That's all I meant in my response to your post.

Secondly, to clarify further: I have been associated with the Fire Service for 35 years, doing everything from grunt firefighter to apparatus mechanic to officer to training officer, blah, blah, blah. I have also worked on dozens of truck committees. So my comparison to over-the-road truck's multiplexing systems was certainly not based on "inexperience", thank you. You however have not presented any evidence to support your OPINION that fire apparatus multiplexing isn't within your comfort zone. Why? If you advised some customers to go with it, and then they had problems, then I could see your not being too willing to advise someone to get it. Is that the case? Or are you just not understanding the technology? Lots of things are multiplexed today, and the manufacturers are constantly striving to improve on what they have developed.

So, bottom line is: I don't agree with your advising "clients" against it, and that's based on my knowledge of the technology, not my opinion.

I would only ask, when you advise against multiplexing, what do you use for documentation to support that position? Sooner or later, you'll run into an educated consumer who will ask just that and back you into a corner......

Sir: I will not get into a back and forth with you on this forum. You have your opinion and we have ours. You can go to our website www.ewfac.com and view our (experience) credentials. I do not need to explain or justify anything to you. Besides, you took the first swing at us because you didn't agree with what I stated in my original post. Whatever your goal is here I'm not the least bit interested in it. This thread is full of both those who agree and disagree with the technology, but I don't see you debating it with anybody but us. Clearly, you have an "issue" with consultants as demonstrated in your previous posts. I thank you for your concern that we will eventually run into an "educated consumer" as you put it, which is condescending to everyone in the fire service, but I guess I should really be thankful that you will not be calling on us. You have yourself a nice day!

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