Dim/Bright Commands and Coupler-Repeaters - Which One Should I Use - Part V
...plus some other information about new stuff in the world of X-10
by Phil Kingery
"When last we met, our hero, "Captain Coupling" had just
won the battle of using multiple repeaters in a house, but that cliffhanger episode came to an end
just as he was ambushed by the sinister "Dim/Bright" problem. The curtain opens and we
see our hero contemplating this riddle...."
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Which One Should I Use, Part V (Preamble)
Well, hello again, you gluttons for punishment. Don’t you have anything
better to do? (I wonder just how many of you are reading this at work, hoping that your boss
doesn’t catch you.) To all of you who emailed me to cast your vote, I thank you. At the end of the
last installment in this (seemingly never ending) series, I asked for your input as to the content
of this chapter. (For those of you who have stumbled into this section of HTINews for the first
time, you may want to back up and review parts 1 through 4, otherwise, this one won’t make a lot of
sense. I have been promising to do an entire chapter on "X-10 Three and Four-Way Switch
Circuits" but I seem to be having a lot of trouble finishing up "complex coupling".
At the end of the last section, I again asked you to vote:
Which One Should I Use, Part V
(Dim/Bright Commands and Coupler-Repeaters)
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Or
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Which One Should I Use, Part V
(Three and Four-Way Switch Circuits)
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I received a lot of emails (which tells me a lot of you are reading
this stuff). Just to point out a few:
From DKJ2@msn.com (David Jahn), "Don't disappoint, write about
Dim/Bright commands, couplers - repeater's. You can write about three and four way switch circuit's
next!"
From dicklb@spiretech.com (Richard Lee-Berman), "It has been
very interesting reading your articles [...]It would be great to hear more about dimming
[...]."
And finally from DaveW3616@aol.com (Dave Weatherwax), who wrote,
"I love your writing style. I wish I could sit in one of your classes. [... I ] vote for
finishing the repeater article."
(Dave must think I pay people who send me nice emails. Sorry
Dave.)
Anyway, most of you really have no idea if I am just quoting the
"repeater" voters and ignoring the "3 & 4-way" voters but please trust me,
I am an honest guy. The votes were overwhelmingly in favor of continuing the coupling exposé.
Therefore, on to the next segment:
Which One Should I Use, Part V:
(Dim/Bright Commands and Coupler-Repeaters
...plus some other information about new stuff in the world of X-10)
When last we met, our hero, "Captain Coupling" had just won
the battle of using multiple repeaters in a house, but that cliffhanger episode came to an end just
as he was ambushed by the sinister "Dim/Bright" problem. The curtain opens and we see our
hero contemplating this riddle....
Before we talk about "Dim/Bright" commands and their relation
to repeaters, we need to be sure we understand the basic of X-10 dimming. When an X-10 compatible
transmitter sends out "A1, A1, A-On, A-On" it doesn’t matter how many times the X-10
dimmer receiver receives the "A-On" command. If it receives it once or twice, it doesn’t
matter because it can’t get anymore "On" than "On". Even if it received 32
"A-On" commands, it still would not be any more "On". That is not the same,
however, when considering "Dim" and "Bright" commands. It certainly does matter
how many of "those" commands are received.
There are about 16 dim levels in most X-10 compatible dimmer receivers.
(Yes, there are some companies like "PCS: Powerline Control Systems" who make some very
nice dimmers that have "micro-dimming" but since time is short, I won’t go into that.) If
a standard X-10 dimmer receives 2 "contiguous" (that means "touching each
other") dim commands, it will drop down one dim step (about one-sixteenth in brightness). But
if it receives only one dim command, then nothing, then another dim command, it will
"not" drop down that same one sixteenth. Instead, the brightness of the incandescent lamp
drops down an imperceptible amount (about 1/128th).
 The
early Pico engineers never considered that a receiver might get its commands from something other
than the original signal directly from a nearby transmitter. Today, however, it is common for large
residential installations (and nearly all industrial and commercial jobs) to have either a coupler
repeater made by X-10 (sold through Leviton as their 6201) or from my company, ACT (our part
numbers of CR230, CR231, CR130, CR131, plus 4 others). When an X-10 signal is "repeated"
by a coupler/repeater, (Figure 1) most commands are accepted by the receivers just as if they had
been directly from the transmitter. Even as larger systems came to be, there was seldom a problem.
Dimming was usually done either directly from the receiver itself or from a nearby transmitter that
happened to be on the same leg (sometimes even on the same circuit) of the home’s electrical
distribution system so that enough of the original signal made it to the dimmer receiver that it
still got the "contiguous" dim commands.
The problem came to light when larger installations were relying only
on the "repeated" signals to do the job. Older repeaters continued to "repeat"
the frames of data in the same way as before.
 In
Figure 2, you can begin to see the problem. Whenever the transmitter sends four frames of
"Dim", the receiver only gets two. Plus those two aren’t even contiguous. If you hold
your finger down on the "dim" button for a longer time, lets say for almost six seconds,
the transmitter may send out 32 dim frames. Any nearby dimmer that receives that original data will
go from 100% brightness to 0% in less than four seconds. Your transmitter continues to send
"Dim" commands even though your "nearby" lamp has already dimmed down to
nothing. But when you glance over to that other dimmer (the one which can only get its signal from
the repeater), it’s still at about 85%. Unless you have very good eyes, you may not even be able to
tell that it is dimming at all.
Okay, how do we help this situation? Both X-10 and Advanced Control
Technologies improved their respective repeaters but in slightly different ways. First, allow me to
explain how X-10 did it?
Most serious X-10 technicians are aware of the "6 zero
crossing" rule. That is, whenever a transmitter is changing from one address to another
address, or from an address to a command, or from one command to another command, it must allow for
a pause of at least six clear zero crossings (three cycles) before it continues. I usually explain
it simply by saying that the receivers need that time to catch their breath. In reality, the lack
of signal resets the integrated circuit’s registers so that it will be able to tell the difference
from one to the other. If there is no such "clear space", X-10 dimmer receivers (those
manufactured by X-10 themselves) will think that they are just receiving more of whatever they got
at first. In other words if you transmit a string of "Dim" frames and then immediately
change to a string of "Bright" frames WITHOUT allowing for a gap of 3 cycles, the X-10
dimmer will think that it is just getting more dimming commands and it will continue to dim.
The X-10 engineers took advantage of this "6 zero crossing"
rule and made sure that when their newer repeaters received continuous "Dim" or
"Bright" data, they would transmit enough signal so that there would never
be more than two blank cycles. In other words, the X-10 repeater (sold as the Leviton
6201) does not really repeat continuous "Dim" or "Bright" data but your X-10
dimmer receiver doesn’t really care. It was a clever solution to the problem. The only time this
does become a problem is when the dimmer receiver is one manufactured by someone other than X-10.
Other companies manufacture "X-10 compatible" dimmer receivers and they may require true
"Dim" or "Bright" data to work correctly.
Now let’s talk about the way we did it. (I may be prejudiced but I
happen to think we did it better.) Whenever one of our repeaters "receives" a frame of
address data (A1, or B5, P12, etc.), it continues to do what it has always done: it
"repeats" that same chuck of data during the next 11 cycles, right over the top of the
second time the original transmitter is transmitting it again. The same is true of standard
commands like "On", "Off", "All-Lts-On" and
"All-Units-Off". The difference is when it detects a "Dim" or a
"Bright" command. Instead of merely repeating it, the repeater "remembers" what
it just repeated and holds that frame of data in its memory. It then "listens" closely to
see if your finger is still on the button. (I know I am explaining this in rather simplified terms
but I think it is better than using only terms that engineers would understand.)
 If
your finger is still holding down the button, our repeater will see the first little
tiny bit of data that precedes all X-10 commands (as in Figure 3). Knowing that you are still
holding down the button, it will again, retransmit the dim data that it was holding. Then it does
the whole process again. As long as you hold your finger down on the dim button, our repeater will
continue to repeat dim commands. The same is true if you were holding down the "Bright"
button, or if your computer-interfaced, intelligent controller (like the JDS TimeCommander) was
programmed to send out multiple frames of "Dim" or "Bright" commands. What is
repeated by our repeaters are true dim and bright frames of data.
The ACT repeaters are pretty quick. Each of them can decide in less
than 2.7 milli-seconds if it has to repeat that "Dim" or "Bright" data again.
Our 3-phase repeaters need to do that in order to repeat the entire frame of data on the other two
phases. (It’s kind of complicated so what do you say we don’t go there. Okay?) No matter how many
frames of original "Dim/Brt" data was originally sent, our repeaters will always be one
frame behind. No matter how clever we are, we have not yet been able to design a repeater that
knows when you are going to send a dim or bright command before you do it. We’re
good, but we’re not that good.
The next time you have a dimming problem in a large installation, you
will have a better understanding of what may be causing it. Also based on this information, I hope
that you can make a more informed choice on what repeaters to use.
STOP THE PRESSES, WE HAVE A SCOOP !!!
The title of this installment has the phrase "plus some
other information about new stuff in the world of X-10" at the end of it. Now is the
time to explain what that means. Everyone in the X-10 world is buzzing about the new modules that
have hit (or are about to hit) the market. These new dimmer receivers have (among other features)
"remembered state dimming". That means that if they are dimmed down to 50% and then sent
an "Off" command, they will "remember" that they were at 50%. The next time you
send them an "On" command, they no longer come on at full brightness (100%) like they
used to. Now they ramp up to 50%. Pretty cool! For every one of us who were blinded going to the
bathroom at 2 o’clock in the morning, we thank you. But that’s not all. These new dimmer receivers
also have "preset dimming" and therein lies the problem. Even though there had long
existed a "Preset Dim" command in the standard X-10 command set, the X-10 engineers
decided to not to use it.
That choice seemed to most of us to be a confusing one. Those companies
that make intelligent front-end controllers had long ago included the existing "Preset
Dim" commands in their repertoire. Before X-10 made their dimmers with "preset"
capabilities, other companies had already built their own "compatible" dimmers that did
use the old commands. Interestingly, there are even X-10 compatible thermostats that use the old
"Preset Dim" commands for temperature set-back. Now X-10 was building new dimmer
receivers that did not use these old commands. Instead, they use a new set of commands using
"extended data". This decision caused ripples in the X-10 industry that have yet to
settle down. Most of the front-end controller guys have now included (or are struggling to include)
these new "Preset Dim" commands into their systems. One down, one to go.
Then X-10 introduced their new modules with "two-way"
capability. What is two-way? That question is not as simple as you may think. Ask
four or five people and you may get four or five different answers. Two-way communication is
inherent in most forms of communications today. When you talk on the telephone you can also listen
to what the other person is saying. You are using your computer modem right now to read this file
on the HomeToys web site. You send commands from your modem to this web site and in turn, this web
site sends this file to your modem (through a myriad of other computer systems, of course). All of
the newer powerline communication protocols (Intellon, LonTalk, etc.) also have "two-way"
communications. Instead of simply "transmitters and receivers" they have
"nodes" and each node is a transceiver capable of both sending and receiving data.
Sometimes "one-way" communication is preferred. When I listen
to my favorite "oldies" station on my car radio, the signal is going from the radio
station to my car radio. But it would be inappropriate and impractical for every car radio to also
be able to transmit back some information to that radio stations. Until recently, X-10 systems were
just like that. Transmitters transmitted and receivers received.
Sophisticated communications protocols require complex duplex (two-way)
capabilities because decisions can be made at many different locations. In the case of some of the
newer powerline communications, the system itself has what is called "distributed
intelligence". That means that there is no one central location in which decisions are made.
Since all the parts must work together and each may have a say in the decision making, each part
(or node) must be able to both transmit and receive data.
I have often found myself in conversations where someone would be
promoting the need for all X-10 devices to have two-way capability. Most of the time they would
advocate this upgrade without fully understanding the true nature of it (or the cost). They may
erroneously think that the simple addition of two-way capability would immediately solve their
perceived problem of X-10 unreliability. Buzz, wrong! Let’s say that your front-end computerized
intelligent controller was scheduled to send out an "A1, A1, A-On, A-On" command at a
particular time of day. A few minutes later, it was also supposed to send out an "A1, A1,
A-Status-Request, A-Status-Request". If it fails to get a response, what does that prove?
Surprising it actually proves nothing. Current X-10 systems, even in very large, multiple
transformer, multiple building systems, usually work very well. They do this because professional,
trained and experienced designers and installers did all the right things to make sure that the
signal gets to all the receivers. In poorly designed systems, unreliability has more to do with
signal strength and noise levels than it does with the lack of two-way communications.
Please don’t misunderstand me. I am not saying that the addition of
two-way capability is a bad thing. There are several situations where it would be of great
advantage. Let’s say that your front-end computerized intelligent controller was scheduled to send
out an "A1, A1, A-On, A-On" command to a wall-mounted receiver at a particular time of
day. A few minutes later, a human being over rides that command by pressing the button on that
receiver, turning it back off. A moment later, with its new two-way capability, that receiver will
be able to send out that information by transmitting "A1, A1, A-Status-Off,
A-Status-Off". Your front-end computerized intelligent controller now knows that the receiver
is off. Now that is an appropriate use of two-way. Everything, however, comes at a cost.
We at ACT were aware that some of the extended code data sent by these
new modules may be a problem for our repeaters but we were not sure just how much of a problem it
would be. ACT and X-10 have been close partners since 1989. In the X-10 world, only 2 companies
make repeaters. Obviously, X-10 Ltd. is one of them, making the 6201 for Leviton. We at ACT
currently make eight different X-10 compatible repeaters: two different ones for 120/240v
split-single phase distributions systems, two for 120/208v 3-phase systems, two for 277/480v
systems, one for Canadian 347/600v systems and even one for 240/415v, 50Hz distribution systems
(only for export).
 We
have sold a lot of repeaters over the years and one of our top sellers has been our CR230,
residential unit (Figure 4). I would doubt that there are many residential customers who give more
than a passing thought about the other functions of our more sophisticated repeaters. While X-10
has long had the "extended code" possibility in their protocol, we at ACT patented our
own extended code (February 1996) increasing the 256 address capability of the standard X-10 to our
own having 4,096 addresses. This new "ACT Code" was done for those commercial customers
who wanted a secure system that could not be circumvented by anyone with a standard X-10
transmitter.
In order to standardize our manufacturing, all of our repeaters have
long had the ability to recognize both the standard (256 address) X-10 protocol, plus our own
(4,096 address) ACT code protocol. The problem is that now that X-10 has expanded on its use of its
own extended code data, we find that our repeaters erroneously recognize those signals as being the
"ACT code". Our repeaters shift into their second mode. Unfortunately, our protocol is
different enough that true frame repeating of the X-10 extended code does not work. When one of the
new two-way modules is plugged in for the first time, it transmits an "I’m Here" message.
Unfortunately, our repeaters do not understand this new "I’m Here" data and things start
going wrong. In other words, our repeaters think that they are repeating ACT’s protocol and in
doing so causes the new Leviton two-way modules to re-transmit their initial "I’m Here"
message, over and over again.
 While
the CR230 is our least complicated repeater, most of our other units (Figure 5) have 8 dip-switches
and additional features to afford system designers many options for complex coupling situations.
One of those dip-switches is labeled "Extended Code Only" [up] or "Both Codes"
[down]. While those industrial customers who have ACT’s "4,096 address" equipment in
place know what that switch means, it is easily misunderstood by other customers who have only
heard of X-10’s new extended code.
It appears that the Leviton 6201 also has a problem. Unlike ACT’s
repeaters, it does not even try to repeat the new extended data. Like other companies who
manufacture X-10 compatible products, we at ACT will also adapt our equipment to take advantage of
the new commands. We have already begun making our plans to re-write our repeater software to
recognize X-10’s extended code. Since the project has just begun I can’t yet report a solution, but
keep your eye on this web site.
(NOTE: As of 08-99 new repeaters now available from ACT have these and many
more new features.)
Sadly, we have come to the end of this episode in our continuing saga
of "Captain Coupling" and not surprisingly there seems to be another cliffhanger ending.
How will we ACT deal with the new X-10 codes? What will become of "Captain Coupling" and
his faithful companion, Phil? And what will be the title of the next episode? Will it finally
be....
Which One Should I Use, Part VI
(Three and Four-Way Switch Circuits)
...or will there be more to the "Repeaters vs. the X-10 Extended
Code" story. Stay tuned.....
Oh, I almost forgot. Last time I asked that you send me any interesting
email signatures. I am often amused by the variety and wit some people show at the end of their
emails and newsgroup posts. I mentally collect them because they make me smile and sometimes they
make me think. Here are a few (of the clean ones) that readers sent me. Some of them have a
distinct Star Trek theme. Some of them are just weird and then there are some that defy
explanation.
Excuse me. What does God need with a Starship?
CAUTION: Don't look into laser beam with remaining
eye.
I want to be what I was, when I wanted to be what I am
now.
I didn't say that I didn't say it, I said that I didn't
say that I said it!
Only those that truly dare, truly live!!!
Life is just a computer simulation.
"Don't speak unless you can improve on the
silence." -Spanish proverb
What if there were no hypothetical situations?
What a relief. Look ma, no hands. As a shapeshifter, I
can say this for real. Odo out.
I smell bacon, I smell pork. Run little piggy. I have a
fork.
As always, comments and suggestions are always welcome. Email me at
pkingery@act-solutions.com
Phillip Kingery is the representative of Advanced Control Technologies,
Inc. and teaches X-10 related classes around the country.
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