XTB-II X10 Transmit Booster

JV Digital Engineering jeff@jvde.us 11-27-07

The XTB-II combines the high-power XTB transmitter with two coupling networks to drive both 120V legs directly. An additional passive coupler is not necessary. The XTB-II is designed for a split-phase 240V system, and its PIC microcontroller can be set to gate off the superfluous X10 bursts used in 3-phase systems. That allows the XTB-II to concentrate all its energy into the X10 burst at the zero crossing, and it can generate a slightly stronger signal than the XTB. Depending on line characteristics, the XTB-II can output over 20Vpp at 120KHz onto the AC line.

The XTB-II has a X10 input receptacle that functions similar to the one on the XTB. A control module such as the CM15A can be plugged directly into that receptacle, and the XTB-II will drive its boosted output onto both phases. It is recommended that no more than three X10 transmitters be plugged into that receptacle. The larger size of the XTB-II allowed room for larger inductors, and the X10 receptacle on the XTB-II can deliver up to 50 watts. An internal fuse will blow if that rating is exceeded by a significant amount.

The XTB-II includes built-in TW523 emulation. A digital I/O line can be run from an automation controller directly to the XTB-II. The opto-isolated digital interface on the XTB-II is functionally identical to that of the TW523. The XTB-II TW523 emulation differs from the actual TW523 in several regards. The XTB-II error checks all incoming data, and does not produce any output when a collision is detected. The XTB-II does not need a gap to separate X10 messages, and it will recognize each pair of bright/dim commands. When enabled, the XTB-II also includes the ability to accept extended messages.

Like the XTB, the XTB-II includes an amplifier to boost low-level X10 return signals. The XTB-II adds a bandpass filter in that path to attenuate to out-of-band noise, but line transients can still make it through the filter, and are amplified. Devices that are sensitive to noise, such as the SignalLinc 1132, may not work well with XTB-II.

ELECTRICAL CONNECTION

The XTB-II does not simply plug into a standard receptacle like the XTB. It should be installed adjacent to the electrical distribution panel where it can drive both phases directly. Connections to the distribution panel are made through one of the two internal terminal strips. The other terminal strip is normally connected to the X10 Input receptacle on the cover. The XTB-II should normally be wired to both phases and neutral through a 240V plug & receptacle fed from a double-pole 15A or 20A circuit breaker. A standard power cord can be wired to Phase I and Neutral for single-phase operation. Ground is not used internally, and is only required if the cover contains a grounded receptacle. A solid connection to neutral is essential to prevent damage.

While a standard 240V 3-prong plug & receptacle are adequate to connect the standard unit, I recommend 4-conductor power cord wired through a 14-20P plug & 14-20R receptacle for the grounded unit. The locking strain relief on the XTB-II will accept up to .4-inch diameter wire. It may be easier to wire the terminal strip with the board removed from the case. #18 gauge wire is sufficient because the XTB-II is internally fused at 2 amps maximum. Check the electrical connections carefully before applying power. It is recommended that the terminal strip screws be re-torqued (with power switched off) to insure solid connections.

XTB-II OPERATION

The XTB-II can either function in the default X10 boost mode or the TW523 emulation mode. It cannot do both at the same time. The XTB-II powers up in the default X10 boost mode, and it cannot monitor powerline signals while in that mode. Any message received from the automation controller will cause the XTB-II to switch to TW523 emulation. In that mode X10 inputs received through the X10 input receptacle will not be transmitted to the powerline unless the XTB-II repeater is enabled. However, they will be decoded, and valid X10 messages will be sent to the automation controller. Interrupting power for several seconds will return the XTB-II to the default X10 boost mode unless Mode 15 is ON. Refer to the XTB-II Mode Options document for more information.

The X10 transmitter in the XTB-II auto tunes itself to 120KHz using the powerline as a reference. By default, it only transmits the X10 burst following a zero crossing. Within that window, the duration of the burst is controlled by the digital input. If three-phase transmission is enabled, the transmission window is open throughout each powerline cycle. European 50Hz versions have 3-phase transmission enabled by default.