Noise and Filtering, Troubleshooting

Which One Should I Use - Part XI

Phil Kingery


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by Phil Kingery

"You want me to stick that filter where?!?!?!".

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Which One Should I Use, Part XI (Preamble)

Gather round, children, the Scheherazade of the HA world is about to spin another yarn of electrons, wires and gizmos galore. As I write this I catch myself thinking, "I hope I can make good on my promise to finish this up in this episode". Unfortunately, I don’t think I’m going to make it. We have a lot to cover in this third part of three (which is really WOSIU#9, WOSIU#10 and WOSIU#11).

Confused yet? Well don’t be. For those of you who are reading one of these "Which One Should I Use" articles, here at HTI, for the first time, please continue reading. (Those of you who are long time readers can  skip the next four paragraphs.)

Okay, how about a little background on "Home Toys" and this seemingly never ending series. Way back a couple of years ago, Bob Hetherington, the all-powerful webmaster of this site, felt that there was a gap in the Home Automation market that needed to be filled. There were already a lot of web sites but they were primarily about specific manufacturers or distributors. Bob felt that there was no web site that talked about all the technologies, all the products, all the new systems, doodads and gizmos.

Bob wanted to create a web site that was better than a magazine. Not only would it keep its readers up to date on what is going on in the world of HA, it would also have all the past issues available all the time. It would be like buying a magazine from your local news store and automatically getting all the past issues along with it. Now Bob isn’t independently wealthy and he can’t afford to do this as a hobby so he needs to make a buck from his efforts. He knew that he would have a hard time charging people to look at his web-zine, so he relies on advertising to help offset the cost of his little endeavor. That’s why there is an advertising banner way up there on top of this article. We also encourage you to let the advertisers know that you saw their ad at hometoys-dot-com.

One thing that Bob wanted to do was to provide his readers with interesting articles. Every two months he has fascinating, enlightening and (at least in the case of my stuff) entertaining features, commentaries and editorials. That gets readers and readers gets advertising.

This edition is the eleventh article in this series. The first one appeared in the December 1996 issue of Home Toys. Bob had emailed me and asked if I would be interested in writing an article for his web site. I had already written an article for a print magazine but I pulled it when their editors wanted to replace my part numbers with a competitors part numbers. I refused. If I was the author, I wanted my part numbers in it. Bob, on the other hand, set no such restrictions (aside from refusing to publish my vacation photos of me on that nude beach…) And so, in a sense, that very first article was intended for someone else. Their loss. Besides these eleven pieces, I also wrote a fluff piece which, to this day is just about my favorite. That one gives my version of the history of HA and is called, "Lucky Lindy Meets My Grandmother". It has been plagiarized many times (with my blessings) in many term papers and newspaper articles. If you are working on a high school or college research thesis, feel free to copy chunks of it for your use. Let me know what grade you get.

Hello to all of you who skipped directly to here and welcome back to the rest of you that took the time to read the little history lesson. You now know a little about how "WOSIU" came about. Back in [June], we talked about "noise", or what I prefer to call "electrical pollution". In that article, I preached the gospel according to Uncle Phil on the subject of noise and I even showed you some examples on the oscilloscope. It was also in that episode that I first experimented with including a short movie that actually shows some noise. I thought it was pretty cool and the comments were encouraging so in the [August] edition, I put in three little movies. Bob really loves those big fat mpeg files since the longer you stay at this web site, the more advertising he can get. Although that was not the intention of the movies, it does have a nice side effect. (Sorry, no movies in this edition.)

Back in August, I showed you the two basic types of filters, the series blocking filter and the shunt filter. In this edition, we will finally get around to some troubleshooting tips and some testing techniques and a flow chart to help you think about the process of fixing a bad X-10 system. Ready, … Set, READ!

Which One Should I Use, Part XI
(Noise and Filtering, Troubleshooting)

Let’s say you are standing in a house in which you just installed about six dozen X-10 devices, and now you discover that they won’t work. Just knowing what noise looks like on an oscilloscope or how a filter can block that noise, doesn’t do you a whole ton of good if you don’t know where the noise is coming from. That is what we are going to cover in this chapter.

fig03.jpg (23141 bytes)I suppose I should scold you for not testing the house before you started, but we are going to let that one slide (you owe me). Let’s first talk about the basic troubleshooting tools that you should have if you are going to be doing this as a profession. The most important piece of test equipment is, of course, your brain. (Ha, thought I was going to talk about test receivers, didn’t you?)

Seriously, the best ammunition you have in troubleshooting X-10 system problems is a good understanding of basic electrical distribution systems, how X-10 works, what things can cause problems and then we will concern ourselves with what test equipment you need to use. Of course, the rules are different if you are a DIY’er (re: "do it yourself-er") rather than an HA professional. The only difference being that a professional gets paid to do it where an amateur does not. Although we all prefer that the professional know more than the amateur, that is not always the case. The word "amateur" comes from the Latin "amour" for "to love". So an amateur does it for the love of it. I know a lot of amateurs that know a lot more about this stuff than a lot of professionals.

So let’s look at this from the point of view of the DIY’er (that’s Do-It-Yourself-er). Let’s be honest. If you are just installing this stuff in your own home, it’s a good bet that you don’t really want to know the "why", just the "how". You are not really interested in learning all the particulars of the system, you just want it to work. Plus there is the fact that most DIY’ers do not have any X-10 test equipment. With no test equipment, we have to rely on a lot of trial and error troubleshooting.

With that in mind, let’s go over some basics. First, there are only a few reasons why a normally operating X-10 receiver does not work, but we’ll get to those in a minute. Notice that I said "normally operating" unit. The very first thing to do if something is not working is to test it. The most difficult system to troubleshoot is one with only one transmitter and one receiver. If it doesn’t work, you don’t know if it is a bad transmitter, a bad receiver or one of those "other few" reasons that we haven’t talked about yet.

Common sense suggests that it is easier to troubleshoot an X-10 system if you have multiple transmitters and multiple receivers but even if you don’t, there is usually a very simple way to see if a transmitter/receiver combination is working. If both the transmitter and receiver are the plug-in type, then simply plug them both into an extension cord (not a self-filtered plug strip)and plug the extension cord into an outlet far from any electronic stuff. Perhaps you have a receptacle in your garage or basement that is on a circuit that doesn’t have anything else on it. If you are trying to test hard-wired devices, then sacrifice a couple of cheap extension cords and wire up them up to those and then plug them into that extension cord.

Do they work now? If they do, then you now know that both of them are capable of basic operation. Now this is not an absolute test. They could work now, but the transmitter could be weak and so it only works when the receiver is nearby. Or it could be that the receiver has a problem and only works with an extremely strong signal. The opposite could also be true. If they don’t work, it may mean that you have so much electrical interference that the two units still can’t communicate even when installed just inches apart on the same extension cord. All of these situations are rare (but I thought I’d better mention them just in case) so lets just say that if they work, you can be 99% sure that they are fine. Of course, if they don’t work, you can be 99% sure that one of them is bad. Now all you have to do if figure out which one.

Simply replace one to see if that fixes it and if not, replace the other. My choice would be to replace the receiver first, since receivers have more moving parts and are more likely to fail. If you have a 5 amp plug-in filter (and almost all installations should have at least one, if for no other reason than to use just for testing), then use it to isolate your test units from the rest of the house. Simply plug it into the wall and then plug your extension cord into it. Even if your house does have every noisy gizmo possible, the filter should help keep it from getting onto your test cord.

Now you have determined that you are working with (as I said before) "normally operating" units. There are only three reasons why they will not work:

1 – Signal appears at the wrong place on the sine, or

2 – Insufficient signal, or

3 – Excessive electrical interference.

The first one (signal at wrong place) only occurs when there is a large accumulated inductive or capacitive loading effect which causes the sine wave to appear to "shift". Briefly, X-10 units in one part of a building don’t "see" the signal at the same time as the transmitter may have sent it. It’s too complicated to go into here (that may be a whole separate WOSIU article for the future). Besides, I have only seen it happen in large industrial-commercial installations and never in a 120/240v split-single phase residential application. We’re going to just discount that one as "highly unlikely".

The second one (insufficient signal) is one in which we have already covered in earlier editions of this series (see Which One Should I Use – Part III "120/240v Residential Coupling", and Which One Should I Use – Part IV, " Complex Residential Coupling with Considerations for Dim/Bright"). Since we have been talking about interference, we will concentrate on the third one, excessive electrical interference.

We instinctively know how electrical interference can disrupt the communication in an X-10 system. After all, it is hard for us humans to hear each other at a rock concert, yet we can whisper in a church. The ability of X-10 receivers to operate in "noisy" environments vary greatly. Most of the Radio Shack flavor of X-10 units are fairly intolerant of noise. Even a small amount of interference causes them problems. Many of the newer units have AGC (Automatic Gain Control) which allows them to work better in harsh conditions. In any event, if you have just installed some new receivers (and you have already tested them so you know they are good units) and they don’t work, you need to figure out why.

One of the best ways to determine if you have a noise problem is to eliminate every possible thing that could be generating noise. And the easiest way to do that is to start at your electrical panel and begin turning off breakers, one at a time. (Make sure that they breakers which power your transmitter and receiver stays on, of course.) There are lots of ways to go about this. Some technicians turn each breaker off, test the system, then turn on that breaker and go on to the next one. This is not one of my favorites since it works only when there is one big source of noise. If there are several sources that disrupt your X-10 system, turning off only one breaker at a time, makes it difficult to find the problem. I prefer turning off a breaker, testing the system, turning off another breaker, testing the system, etc.

Once you have determined the circuit (or circuits) that are your nasty ones, now you need to figure out what device on that circuit is to blame. One piece of advice. Don’t think that an electronic device can only generate noise when it is "on". If you suspect a particular electronic gizmo (TV, fax machine, computer, etc.) don’t just "turn it off", unplug it !

Once you have determined what electronic gizmo (or gizmos) is causing your problems, you will have to filter it. The most common filter in these situations is the common 5 amp plug-in filter. The ACT part number is the AF100 (and yes Leviton and X-10 and X-10 Pro all have similar products). Occasionally I have found some things that are generating so much interference that one filter doesn’t quite do the job. The AF100 is a 40:1 ratio filter. That means that a 400 milli-volt noise (in the range of frequencies that most effect X-10 systems) will be stopped by the AF100 with only about 10 milli-volts escaping through it. If the noise level is extremely high, say over 3 volts in amplitude (which I have only seen in rare industrial installations) then 75 milli-volts will still sneak through and that is enough to cause you grief. For almost all common residential noise sources, a single AF100 is more than sufficient.

Well, if you are a DIY’er, that is the basics of troubleshooting, but what if you are running a Home Automation business. You are an HA professional. If that is the case, you should have test equipment and experience and training. Many HA professionals don’t, but let’s say that you do. Anyway, let’s pretend that all of you reading this are HA professionals. With that in mind, let’s proceed with a basic discussion of troubleshooting from the professional’s point of view. Lets go over this section by section.

Troubleshooting Checklist:

First - Be comfortable with the equipment before you go to your customer’s location.

  1. Have a working knowledge of X-10 (and related compatible equipment) from personal experience and test bench work.
  2. Have a good working knowledge of electrical distribution systems, panels, wiring, etc. and work with a licensed electrician (unless you are one).
  3. Remember, your customer is not paying for you to learn on the job. They are paying you because you are supposed to already know how this stuff works.

Second - Have the appropriate test equipment and know how to use it.

  1. Have an X-10 test transmitter and test receiver (and perhaps even a spare test receiver) and/or another appropriate test unit (like the nifty Monterrey unit).
  2. Have additional test "stuff" that helps with troubleshooting (like tools, multi-meter, alligator leads, etc.).
  3. If appropriate, have an oscilloscope and test box converter.

Third - Ask questions! Gather as much information as you can.

  1. Find documents, charts, diagrams, prints, layouts, etc.
  2. Find out how long the system has been installed, how long it worked properly and when it began failing.
  3. Get specific answers as to exactly what has failed and when. If it is an intermittent problem try to establish a pattern.

Obviously the above suggests that you are being called in to fix a system that was installed and was working in the past and now does not. Most of the time, however, the troubleshooting takes place while you are installing the system (or parts) for the first time. Even so, sections of the chart are still valid.

One more chart and we are going to call it quits for this episode. This little one is a simplified flow chart that is helpful when troubleshooting a large installation but you may also find it useful in smaller ones. If you would like to view a larger one, with more detail, then down load this large version.

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Okay, guys and gals, its confession time. I am not very happy with this article. If I had more time, I think I would delete this whole thing and start over. It has almost no graphics. It just doesn’t seem to flow very well, it doesn’t seem to inspire me, but sometimes, I’m my own toughest critic. Unfortunately, the HTI deadline is upon me (let me look at the clock…..yup, here and gone…..Bob’s not going to be too happy with me) so whatever it is, it is.

I sincerely hope that I am not so rushed next time because I want to finish this up. In the next chapter, we will cover some test equipment, a little more on shunt filters and finally (I promise), whole house filtering.

One of these days, I’m going to get my articles in on time…..maybe!

Oh before I forget, begin thinking about a subject for the article after the next one. I want to write what you want to read. You have to let me know.

Will Captain Coupling change his name to Captain Filtering?

What’s this we hear about a new ACT 15 amp plug-in filter?

And when will the next ACT class be held?

Stay tuned, children! Same Bat Time, same Bat Channel!

Phillip Kingery is a representative of Advanced Control Technologies, Inc.
and teaches X-10 related classes around the country.
Email him at

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