X10 Transmit Buffer (XTB)

Here’s an interesting X10 amplifier project. Most of us have experienced X10 signal propagation problems at one time or another, so anything to help the signals get through is welcomed. No mention of a 220V version but as it’s a DIY project it may not be difficult for someone to redesign for European modules?

“Every once in a while you come across a product so useful that it changes the fundamentals of how you live and work. Recently, I had the opportunity to help beta test fellow newsgrouper Jeff Volp’s XTB (X10 Transmit Buffer) and I can say without hesitation that this is one of those “breakthrough” products. Anyone who has an even moderately complex X-10 based system has more than likely been sucked into the netherworld of signal attenuation. Transmission problems are the work of a variety of demons, pixies and Orcs that inhabit the average home’s power lines. The XTB is like a mighty electrical Excalibur, capable of slaying the motley army of X-10 demons with a single slash.

What is it? Well, it’s almost like the mythical carburetor than runs on water. If it were a rifle, you’d never miss. If it were a cell phone, your calls would never be dropped. If it were a power drill, you’d be able to punch through stainless steel ingots as if they were butter. The XTB is an amplifier unlike any you’ve ever seen. It takes the real-time output of an X-10 transmitter like a TM-751 or a CM11A and turbo-charges it to previously unheard of levels in the X-10 world. (At least I’ve never heard of them!) The output is so high that both my Monterey Signal Analyzer and my ESM1 bar graph meter “pegged” out at their maximum levels (4v for the former, 5v for the latter) at a considerable electrical distance from the XTB.

It was fairly easy to calculate the voltage based on extrapolation. I compared the voltage drop between point X and Y with a weak transmitter like the CM11A. Then I repeated the readings with the XTB. Based on the output voltage, I concluded that the signal exits the XTB at 22 to 24v. Admittedly, it’s nowhere near as precise as an o’scope but the attenuation ratios are fairly consistent in my house for point to point readings. If the CM11A clocked in at 50mV at a particular receptacle, adding the XTB would boost that reading to .25 volts, or about 5 times the original signal strength

Even with 10 X-10 filters deployed throughout the house, my humble abode is an X-10 nightmare. Lots of X-10 transmitters, lots of PC and hi-tech gear, lots of UPSs, switching power supplies and other tiny, twisting passages for X-10 signals to get lost in. In short, a house full of X-10 demons, ready to absorb or corrupt an X-10 signal at any time. I’ve gotten used to the fact that my wife’s sewing room was beyond the reach of X-10. She’s actually glad that it is. When I plugged the Maxicontroller into the XTB ­ the sewing room lights flashed on and off even though they never had before. The signal, as read by the Monterey, was a fairly low (but still very reliable) .11 volts. But what was more peculiar is that the sewing room was on a different phase than the Maxicontroller. So what was coupling the phases?

I decided to check at the panel. All of the circuits on the phase opposite the transmitter were evidencing a steady .11 volts. I turned off the central AC breakers, expecting to see the Monterey read 0 volts. No change. Steady .11 volt signal. I turned off the furnace. No change! I shut down EVERY breaker in the panel except for the meter and the TM751/XTB combo. That would surely reveal the “good” elf that was somehow coupling the two phases of my house. But once again, there was no change.

After a flurry of emails to Jeff, it became clear what was happening. The XTB signal was SO strong it was coupling at the pole transformer! That might not be the case with other houses. My power pole transformer is less that 100′ away from the breaker panel.

I threw the XTB every curve I could think of, rummaging through my box of X-10 goodies for test candidates. I tested the XTB against several flavors of transceivers, from the RR501 to the TM751 and even the Robodog. If you’ve got more than one transmitter, you may need more than one XTB. Unlike Smarthome’s BoosterLincs, the XTB will only amplify signals from the device(s) plugged into the unit’s outlet.

While you can’t plug in a vacuum cleaner into that outlet, you can plug in a power strip and have the XTB amplify several devices plugged into that strip. I’ve currently got a CM11A, a TM751, a TW523 and a SmartMaxi-controller plugged into the outlet strip without any apparent issues. I even plugged a CM11A into the XTB and then a TM751 into the CM11A ‘s pass-through outlet without a glitch. I’ve also tried the Leviton All Housecode Transceiver, the X-10 Mini Timer, Mini-controllers, and the IR543. All worked without incident. The SmartMaxi (All Housecode Maxicontroller from Smarthome) with its macro capability was particularly enhanced by the XTB.

One of the nicest benefits of the XTB is that it may allow you to kiss your active repeater goodbye. I disconnected my Leviton repeater a long time ago because it would lock up far too frequently for reasons I could never quite pin down. I avoided needing a repeater (or even a coupler) by using TM751’s spread throughout the house at the very end of each circuit. This kept them from interfering with each other, mostly, but it really created problems using a CM11A or TW523 based controller like the Ocelot. There was no way to insure that the output from either unit was able to reach all of the circuit ends — until now, that is. The XTB is certainly going to change the way I’ve got my X-10 units deployed but it will be for the better in the long run.

The XTB also turns out to be a very useful adjunct to my X-10 power line meters. With the XTB plugged into an outlet about 10’ from the panel, I see a signal everywhere in the house, which is about 1000 sq. ft. That’s been pretty helpful in finding unusual signal suckers because I can see a signal and calculate the attenuation whereas before the signal would be too weak to even register on the meters.

I’m sure Jeff will fill in the pricing details and all the usual warnings. I’m starting off with two assembled units because of my less-than-sterling solder skills. I’ll probably even try building one of my own with a little help from a better solderer since there are surface mount components that have to go on the board towards the end of the assembly process. I recommend buying at least one assembled one. If there was a program called “This Old Circuit Board” Jeff would be one of the hosts. I showed the XTB to a friend, asking him if he could solder one for me. His comment was “not like that ­ that’s perfect!” He was floored by the how neatly Jeff had assembled the beta. So was I.

If you’re looking for an X-10 dragonslayer get yours hands on Jeff Volp’s XTB.”

X10 Transmit Buffer – http://jeffvolp.home.att.net/xtb_files.htm

8th June 2006 – Jeff has added some comments about 240V operation in the assembly notes here – http://jeffvolp.home.att.net/x10xmtbuf/xtb_assembly.htm.