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The XT-Module was developed for the operation of a DC car system without the use of a PC.

XT stands for Extension and describes the possibility that vehicles equipped with a DC-Car decoder actively transmit data and primarily serves as an independent control unit to perform individually adjustable functions that are desired after the “evaluation” (receiving of IR signal)
In addition, it converts the received signals and makes them available in various formats for further processing.
For example, for feeding into a feedback bus or for evaluation with software on a PC.
The following features are currently available:

  1. Control of a servo crossover (2-, 3- or 4-way crossover selectable)
  2. Switching a contact to ground/GND
  3. Sending out a freely selectable DC-Car infrared command

Typical Applications

Here are some possible applications:

  • Emergency vehicles unlock their own way (driving over red lights)
  • Overtaking vehicles
  • Control of junctions by indicator evaluation (junction automatically turns in the direction in which the vehicle flashes)
  • Control of a bus stop bus bay (bus turns the turnoff itself)
  • Sorting out vehicles (lorries are not allowed to enter inner city traffic)
  • Distributing the vehicles at a parking area
  • Distributing the vehicle at a fire station, bus station, etc.
  • Sorting out vehicles with an empty battery to get to a charging station in conjunction with a software, a fully automatic charging process is possible)

All this “Magic” is made possible by information sent from the vehicle via an infrared connection to the XT Module that works in conjunction with the a DC car decoder (decoders supported: DC07, DC08) installed in the vehicle.

The following information will be provided by a dc-car equipped vehicle:

  1. Vehicle number (1-31)
  2. Vehicle type (1-15)
  3. Status of the blinker on the left
  4. Status of the blinker on the right
  5. Status of warning indicators
  6. Status of the front flashers
  7. Status of the battery

Decoder from DC07 or DC08 is a prerequisite for sending information.
Generation D05, DC04 and older are not supported.
Decoder transmits via an infrared LED (connected to the MF 5 connector)
The spotlight should be mounted approx. 2 cm in the front bumper.
Alternatively, the infrared distance emitter can be used.

1. Basic Decoder IR LED Connections

DC08 Decoder has built in resistor on board. LED can be connected directly.
DC07 Decoders require a resistor

2. XT-Module Connections

Power supply:
The DC-Car-XT module requires a DC voltage of 5V / 500mA for operation.
This can be fed either via the screw terminal strip or the mini USB port.
The USB jack is for this purpose only. No data can be received or transmitted via this socket!

*LED indicator blue (right) and green (left) The green LED indicates the presence of the 5V operating voltage.

The blue LED lights up for the period of time when a valid signal has been received. *Reed contact. This port is used to reset a triggered function.

For example, the switching contact is switched off or a servo branch is reset. The reed contact must be switched to ground/GND.

*Phototransistor (+ and -) Here the phototransistor is connected correctly to receive the data.

*Infrared LED
Here the negative pole (cathode) is connected to an infrared LED, which emits a freely selectable DC-Car infrared command.

For example, stop, blinker on or above. In addition, the time can be set for how long the IR command is sent out.
Attention: A pre-resistance is already on the board and does not need to be added externally!

*Switching transistor
Here a relay or other consumer can be connected, which is switched on.

Please note that a ground connection must be established between the XT module and the control electronics of the respective consumer. For example, you can use it to go to the switch attachment of a servo decoder or traffic light decoder and thus trigger functions. *Servo connection
The servo connection is used for direct control of a model construction servo through the XT module.

You can connect all common model building servos here. Please note the correct connection order, as these may vary with the different manufacturers.

*Connection for CV programmer
This 8-pin socket is used to connect the module to the DC-Car CV programmer.

This is required in order to be able to configure the XT module individually with the software “CV-Programmer”.
It is the same program and hardware that is also used to change the CVs of the DC Car decoder.

*Vehicle data serial and 8-pole as well as 5-pole
socketThese connections are used to forward the received data to a feedback bus or software.

They are output either serially (connection to the terminal strip) or binary (8/5pin socket).
Please note that you must use a power supply/power supply with at least 500mAh, otherwise the servo that may already be connected will pull the voltage down and the XT module will not be able to be reached by the
Alternatively, you can connect the servo afterwards. This is no problem due to the practical 3-pole connector.

3. Infrared Send – Receiving Distance

Vehicle mounted IR sensors

Typically the IR LED is mounted on the underside of the vehicle, while the phototransistors is hidden in the roadway.
The advantage of this type of assembly is that at the moment of evaluation, foreign light influences can be almost excluded, since the vehicle completely covers the phototransistor.
The disadvantage is that the phototransistor can be covered by dust, impurities, etc. In addition, the transmitting LED must be positioned very precisely, because due to the short distance, control is only possible to a limited extent.
Another variant is the mounting to the right side of the vehicle radiating sideways.

In the case of left-hand-drive systems, the assembly should of course take place on the left side.
Due to the greater distance between transmitter and receiver, the tolerance at the mounting height is significantly higher and the installation is easier to accomplish.

External IR Sensors

Xt leitpfosten.png

A phototransistor is required to receive the data of the send LED. Here, too, you can fall back on the tried-and-tested DC-Car components.
Simply use a phototransistor of the DC Car Distance Control. This can be mounted well camouflaged on the side of the road.
For example, trees, shrubs, buildings, parked vehicles or guide posts are suitable for this purpose.
The distance between the transmitting diode and the phototransistor should not exceed 5cm.
This ensures reliable transmission even at high speeds.
The phototransistor is connected to the DC-Car-XT module with both cables.
Installation location of the transmitting diode

5. Connection to a PC feedback system

In order to transfer the data received from the XT module into a feedback
bus or PC for further processing, there are three options:

1.) Serial output

  • the received data is output as a serial signal at the pin “Serial”

2.) Switching output

  • the switching output can be connected to the input of a feedback decoder (S88®, loconet® etc.) and thus can be easily achieved further switching operations or visualization in a model railway control program (e.g. WinDigipet®, Traincontroller®)

3.) binary signal

  • The XT module provides a total of 12 outputs, through which the received vehicle type and the vehicle number are output in binary coding.
  • These outputs provide a ground/GND signal, which allows a direct connection to the switch attachment of a servo decoder.
  • A valid signal is defined by a test bit and output “valid” at the output.
  • If the XT module is configured to Light Control, the battery and lights values are output on the “Vehicle Number” jack.
  • The value for the warning indicator is the addition of blinkers on the left + blinker on the right.

Application example:

The vehicle with vehicle number 9 and class 3 is recognized, a signal is sent at the following outputs: number evaluation: vehicle number value 1 + value 8 = 9 generic evaluation: genus value 1 + value 2 = 3

7. Parallel output as continuous signal

XT module from 3-2020
By CV24=4 or 5 can be read on the 9 bits genus and number.
This makes further controls feasible.

  • Control of the switch set for servo decoders or traffic light decoders
  • Control of Tiny circuits: Stoptiny, AS-1, etc.

8. XT module test mode

CV23 = 0 Normal
CV23 = 1 test mode reset in the XT module sets CV23 to 0 .
Test mode:
All output signals are switched on or off every second.
Transistor, blue LED and IR LED are also switched.
The servo moves back and forth.
No reception via the photo transistor.

No reed
contact function test mode can only be switched off via the CV programmer.

9. XT module serial output

The serial output on the XT module does not provide an RS232 signal (+15V-15V). A TTL level 5V + or 0 is available at the output. With a CV programmer USB, the data can be read via the update jack.

It also works with a special USB-TTL adapter cable.
Setting the XT module: 9600 baud 1n81, 1 start bit, N parity bit, 8 bit, 1 stop

Vehicle number 1-31

H80-9F 10000000 to 10011111


Genus 1-15

HC0-CF 11000000 to 11001111


Light evaluation

HE0-EF 11100000 to 11101111

ZZZ08 Front flashers4 right blinker2 left blinkers1 Battery test

The most evaluable are as:

H8…CV113 Hc…. CV100HE…. CV27/CV28
NumberNumber GenusLights
016 0 = GeneralBattery alarm
117 1 = Truck shortLeft blinker
218 2 = truck longRight Binker
319 3 = Truck with trailerFront flasher
420 4 = semi-trailer
521 5 = Tractor
622 6 = Agriculture (tractor, etc.)
723 7 = free
824 8 = van (sprinter, etc.)
925 9 = Cars
1026 10 = Emergency vehicle IR off
1127 11= IR emergency vehicle on
1228 12 = free
1329 13 = garbage truck, mail, etc.
1430 14 = Bus IR-off
1531 15 = Bus IR-an
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