X10 Limitations
CM11A

If you have come to this page its most likely because you have a problem with HCA or X10 control in your home.  To get started in resolving your problem please choose one of these options:

1. I have a problem with installing HCA or connecting the X10 interface
2. X10 control of devices in my home is intermittent - sometimes I can control devices and sometimes not
3. I think I've found a software problem with HCA
4. It's something else

Installation problems

One of the hardest problems you can have when using a PC is resolving communication port problems.  Unfortunately each computer is different in the hardware that it uses.  It would be nice to be able to provide exact details of getting a recalcitrant serial port to work, but we can't.  If you are having problems getting HCA to recognize your port selection you need to work through this with the resources available from the hardware manufacturer of your computer or communications addin card.  If you are having problems with the Marrick LynX-10 PC addin card, try the resources on the Marrick Limited web site.

The following are the five most common installation problems:

Problem: The HCA software did not install without error on your computer

HCA installs on computers running the Windows Operating System.  Supported OS version are: Windows 95, 98, Me, NT, 2000, XP, and Vista.  While we test with beta versions of Windows when they are available, we can't guarantee that they HCA works on these unreleased Windows versions.   Make sure that you have the correct operating system. Also make sure that no other applications are running on your computer when you install HCA.

Problem: All the communications ports are in use on my computer

In this case you need to add another communication port. Many different manufactures make addin cards for communications ports. Google for online sites that sell communication addin cards and cables. Before purchasing an addin card make sure that your computer has an open slot for it.

Problem: When I use the Test Hardware Connection button in HCA I get an error saying, "The port you chose is not available"

This message tells you that HCA can’t open the port you selected. Possible reasons for this are:

Problem: When I use the Test Hardware Connection button in HCA I get an error saying, "An error has occurred writing (or reading) to the port you selected"

This message tells you that HCA can open the communications port but when it tries to send or receive data using that port it fails. Possible resolutions for this problem are:

If HCA can open the communications port, and that port is connected to your interface, but HCA still reports an error there is a small possibility that the X10 interface or one of its cables may be bad.  This is a remote possibility - but it can happen.

If you are using the CM11A/HD11A there are some known problems that make it appear that the interface is dead.  Click here to read about these problems and possible resolutions.

While serial communication problems arise in few installations, that fact is of little comfort if you are one of the few.  Resolving these sorts of problems are the most difficult for technical support to resolve as it always is something specific to the computer you are working on or the interface you are trying to work with.  Be assured that we have tested HCA under all the supported Operating Systems, on a variety of computers, and with a variety of interfaces.  It does work.  With some diligence on your part and with some help from technical support it should be possible to get HCA working.  However it can be a frustrating experience.

Intermittent Device Control

One of the most frustrating problems to solve is a device that is not going on or off as expected.  It is hard to know why.  It could be HCA.  It could be the power line interface.  It could be a signal propagation problem.  It could be noise.  It could be a problem with the device itself.

This problem is even more frustrating when the computer can't seem to turn the device on and off, but you can from simple X10 keypad or timer.

For these problems to be resolved you must be a detective.  A detective works in a logical ordered manner.  Starting with a whole list of what could be wrong and working methodically to remove one possible explanation at a time.  With effort, you will be able to eliminate many things that are not problems and, hopefully, be left with a single cause that you could fix.

Let's start by focusing on the software, computer, and power line interface.

In order for the computer to control the device many things need to happen. The HCA software has to instruct the communications port on the computer to send a signal to the power line interface.  The power line interface must receive the signal and place the command on to the power line.  Then the device must receive it.

It is hard to know where the problem is because there are so many layers. Does HCA send the right stuff to the communications port?  Does the power line interface receive it from the computer?  Does it put the signal on the power line?  Once we know that the signal is on the power line then we can eliminate HCA, the computer and the power line interface.  Later on we can see why it doesn't reach the device.

The best tool for this part of the investigation is a signal meter.  The fanciest ones can see the signal, measure it, then decode and display it. Problem is they cost a lot.  This link will show you a less expensive one that measures the signal but doesn't decode it.  We use it here at HCA central in our testing lab.
http://www.smarthome.com/4813.html

By plugging the signal meter into the power line some place close to the power line interface attached to the computer you can see when you use the HCA user interface to control a device if a signal is being put on the power line.  When using the HCA user interface, if you never see signals being placed on the power line for any devices then the problem lies in the software, the computer or in the power line interface.  HCA Technical support can help with this.

This is the most IMPORTANT point of your testing.  Until you know if HCA is placing a signal on to the powerline at the time you expect it to, you will not know if it what is wrong is on the computer / HCA / power line interface side, or after the power line interface and the signal is being lost in your home some place.

Let's assume for this discussion, you have shown that you do see a signal on the power line when you expect HCA is sending it.

Next we have to deal with why the signal doesn't control the device.  We know it is being placed on the power line.    The simplest reason could be that the address you are sending the signal to is different than the address of the device.   Sounds obvious!  But mistakes like these happen all the time.  The device in HCA is set to, for example, C1 and the switch in the wall is set to D1.  Check the most obvious things first.

Second, the device could be broken and no signals will activate it.  The way to determine this is to use another transmitter besides the computer to send a signal to the device.  If neither transmitter can activate the device, then it is a good bet that the device is broken.  A good tool for this is the X10 mini or maxi controller keypad. This can be plugged in close to the device so that you can know that the signal generated by the keypad gets to the device.
http://www.smarthome.com/4020.html
http://www.smarthome.com/4030.html

If the device works then we have are left with the hardest problem of all. Why, when you use a keypad to control the device, does it not work when you try and control it from the computer?

There are four possible problems that could be causing this.

First, it could be a signal propagation problem.  That is, the signal that the power line interface generates doesn't reach the device at a sufficient level to control the device.  This can be very common.  If you can control some devices but not others this is a likely cause.

Second, noise on the line could corrupt the signal so that when it reaches the device it doesn't recognize it.

Third, the signal could collide with other signals being transmitted and become corrupted.

And fourth, it could be a combination of the other three possibilities. Unfortunately, it usually is this.  So in our discussion we will deal with all three at once.

The primary problem is that no two X10 signals are alike.  What you get out of a keypad is not the same as what you get out of the power line interface connected to the computer.  Why? Well, they have different implementations of their transmit circuits so they generate slightly different signals at different power levels.

Also, no two X10 signals placed on the power line at two different points are the same even if generated by the same transmitter.  The two points you choose may be on different branch circuits or, at the very least have different wire lengths to the target device.

If your home doesn't have a coupler or amplifier / repeater connecting both sides of your power panel, you will have problems.  You may not know this, but all of your branch circuits in your home are divided into two groups. Signals sent on a circuit in one group have a really long path to get to a circuit in the other group.  This is what a coupler or amplifier / repeater does - it shortens the path.  More information can be found here:
http://www.smarthome.com/4821.html
http://www.smarthome.com/4823.html

Next we have to think about what happens to the signal as it moves down the wire.   One branch circuit may have many X10 devices - each one absorbs a bit of the signal strength - and another branch circuit may have few or no devices.  So if you place a signal on the heavily loaded branch circuit it may not make it to the target device.   If that signal was placed onto a little used circuit it would make it to the device.

The heavier you load the line (circuit) the more signal absorption you will get. This is not unique to X10, it's all type loads. Each device you put on a circuit will introduce two things, first a higher current draw on the circuit, and second more resistance. Every X10 device you put on the line does indeed attenuate the signal in the rest of the circuit. This will result in most cases increased current in the circuit and more resistance, both of which makes it more difficult for X10 devices to decode the signal. The problem is worse with each device added. Also, some X10 devices themselves generate noise.

If, for example, you were to go to that circuit and plug in another X10 device and you just done all of the above - increased the current draw, add more resistance, and attenuate the signals.  If you're near the thresh-hold on that circuit the new X10 device may or may not work.  Let me say that again: Just adding a new device to a circuit may cause everything to stop working.

And often the worst circuit in the home is the one the Computer X10 interface is plugged into!  That is because that circuit has the computer on it with probably a surge suppressor someplace - a big signal sink.  If you are like most folks you have lots of other electronic gear plugged in to that circuit which adds lots of noise and signal attenuation.  Home Entertainment Centers are the worst.  If noise is a problem, one way to solve it is to put a 10A filter into the outlet then use power strips for the things to plug in. This should be done with any electronic equipment because even though it appears to be off, it is really still on and still generating noise on the line.

Generally you'd have to have a circuit really loaded with a large number of devices before you started pulling down the signal but some devices are indeed worse than others.   Your power line interface should be on a circuit that is as free from other electronic gear as possible.  For example, your power line interface should not be on the same circuit as your Entertainment Center even if it's filtered.

Again, the best tool for to help with signal propagation problems is the signal meter.

A problem with signal meters is that what you want to do is to place it at the exact point where the signal is to be received.  This is easy to do when it is a plug in module you are having problems with and harder to do when it is a switch.  You will need to do some detective work to see if there is a receptacle outlet on the same branch circuit as your light switch so you can get the signal meter close enough to the destination so the test is meaningful.  Then generate the signal from the computer and take note of the signal strength.  Now use a keypad controller and see what the signal strength is received at that same point.  They probably will be different. Is the computer signal so low that the switch doesn't respond?  That's what we need to know.

Before we look to solutions there is one type of problem we haven't talked about:   Collisions of signals on the power line.  Because of the way X10 signals work, transmitters don't know if the signals they transmitted were messed up by another transmission on the power line.  This can happen in odd ways.  For example, you turn a light on in a hallway.  The hallway has a motion sensor.  Many of those motion sensors transmit when it gets light and when it gets dark.  If it is at night - or a dark day or dark part of the house - each time you send a signal to turn the light on, the motion sensor transmits.  If you are doing a series of commands on the power line, subsequent commands after the hallway light may not be received correctly by their target devices since the motion sensor transmission messed them up.

Finally, remember that your problems can be intermittent.  Turning things on in the morning can work fine and in the evening things don't work at all. How could that be?   Because at various times in your home different things are on and different things are off.  One home we worked with had compact fluorescent lights that when on in the evening totally destroyed the X10 signals.  HCA was able to control everything in the home until dusk when the lights went on and then it all just stopped working.  This was, as you can imagine, very hard to find.

So, what's the answer? First, locate as many obvious noise sources as possible: TV, CD, DVD, computers etc. and isolate them with filters. Second, and most people won't like this, use as few 2 way devices as possible to reduce collisions.

Be prepared to buy lots of filters.  Chances are you'll spend more on filters than you did on your power line interface. Some folks have them all over the house.  One tip is to not forget the microwave.  You need a 15A filter on those as they draw 11 to 15 amps.  When the microwave is on, it generates both power line noise and RF noise and is generally the biggest noise maker in your home.

When you think about it what we are really trying to do is to run a communications network over the existing power lines which of course they were never designed to do.   Nor were most of the devices plugged into the power line designed to be noise free. This leaves us with a very noisy network in which devices can become intermittent or not work at all.

The only truly reliable device for finding and fixing noise on the power line is an oscilloscope so you can see the noise and the X10 signals and essentially "tune" your power line for max through-put and minimum noise. This is obviously beyond the scope of most folks but in some homes a
professional automation installer will do this.

Getting X10 to work can be a challenge.  The important thing to remember in your testing is to remember that all X10 signals on the power line are different if produced by different transmitters at different locations. Work slowly and carefully. Eliminate things so you know that they are not the
problem.

Software problems

If your problem seems to be a software problem, make sure that the way HCA works is the way you are expecting it to work.  Review the appropriate section of the User Guide for the feature you are working with and review the contents of the readme file that contains any manual updates.  The readme was installed in the same directory that contains HCA.EXE.  Finally, review the User Guide chapter 17 - Getting Help.

Other resources to help you resolve software problems are:

If none of these resources help you resolve your problem you can send email to Technical Support using the problem reporting form.

Some other problem

If none of the resources you have looked at, and none of the suggestions given help to resolve your problem don't panic!

Whatever you do don't give up!  Sometimes problems that you are seeing have been experienced by other HCA users and there may be a known work-around.  Send email to Technical Support and maybe a quick and simple resolution can be found.

Before sending email, try writing down exactly what you've done and any error messages you receive.  Sometimes just revisiting the sequence of events that led up to your problem is enough help to see where you went astray.  Anyway, composing an email message with the most information possible in the clearest form that explains your problem helps our technical support staff find a resolution as quickly as possible.

Problems can be reported to Technical Support using the problem reporting page.