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Train detection and feedback control with the Lenz System

Film a quick look at the components:

The Lenz feedback system and train detection for PC Programmes

Most PC train automation programmes work in the same way - an overall layout schematic shows all the important features of the layout - points signals and train detection rails.  From this information the programme allows you to create routes and in these routes you can specify which points and signals are changed and what happens when the train passes each detection point on that route (Speed up, slow down, stop, change direction, operate locomotive decoder functions among others).  You can also enter all of your railed vehicles into a database so the computer can show what it is controlling.  It is worth investigating the different programmes out there to get a feel for which would be best for you.

Train detection for a PC controlled shuttle line

We start with a simple arrangement for a popular train automation - a train shuttles between two terminus stations.  This can be done with two detection points as in figure 1.  How the train behaves can be fine tuned in the PC programme, but it is worth noting that a good positive detection is reliant upon the locomotive pick ups and the cleanliness of the track.  You will see that the trains stops at slightly different places each time especially as the running speed of the shuttle increases (Detection may not always be from the 1st axle as it enters the section and the stop command may not be immediately received cleanly by the decoder).  More precise control can be achieved by using another detection section to bring the speed down before it enters the stop section (See figure 2).   

The Feedback scheme needs to be designed around the trains you wish to run on that track.  In the examples above a railcar or a loco hauled train with coach lighting or a cab control car with headlights will be detected and  they enter the sections, however a loco pushing un-powered coaches in front of it may only be detected once the loco enters the section so the detection rails will have to be positioned correctly for the train to align with a platform convincingly (See figure 3).

Detection for a through station

Figure 4 shows how to monitor a small station on a line with travel in both directions - it also shows that the PC does not have to use every detection point on a line unless you want to change the state of a train - the route for a through train will ignore the monitored sections.

Block sections

Block sections allow you to run multiple trains on the same line and avoid collisions.  Figure 5 shows a typical set up:

A block section needs to be long enough to hold the longest train running through it - it is also important that that train can be halted, from speed if the next block up the line is occupied.  Your PC programme routes settings can allow you to tailor the control of individual trains so that they can behave realistically in a block section system.

Monitored sections and Junctions

Do not put monitored sections across your points (Turnouts).  These should be powered from the main track bus.  If a point is monitored then the PC programme will show both possible routes as blocked even if only one track is occupied.  See figure 6.

Using train detection efficiently

You do not need to wire the entire layout for train detection.  You only need detection tracks where you want the behaviour of the trains to change (Start, stop, accelerate, decelerate or control of decoder sound and light functions).   In most cases only one detection section is needed, however for more precision you can use more sections.  An example of this is a station stop where you want the train to stop precisely alongside a platform -  the first detection section will be used to slow the train to a crawl and as soon as it enters the next section a stop command is sent - your locos will then stop at the same position every time.  Just bear in mind that the train detection system is the only way that the PC programme can see what is going on with the trains on a layout.  The whole system works so long as you tell the PC programme what it is dealing with.  The programme relies on being given the correct starting information.  The detectors only show if a power consumer is present or absent - as a train progresses through a route each detector will light up in turn until the train reaches its destination.  If the routes, track plan and train information is correct at the start then the PC will keep track of everything.   If you manually move a loco by hand or using the DCC controller, you must tell the PC programme where it is before you start automatic running again.​​ With that in mind the power consumption detection system is very reliable.

Bi-directional communication such as RailCom offers the possibility of train detection knowing which loco decoder is actually at each detection point.  Some programmes already use RailCom or transponders to a certain extent.  As yet no programme responds to incorrect decoders turning up at a a detection point - this is mainly because a train can consist of multiple decoders, sometimes with different addresses.  It can then become very complex to explain right and wrong detection conditions to a PC so that it can resolve incorrect detections.  In most cases a PC programme will throw up an "incorrect loco in section" message and shut down the automation until the issue is manually corrected or overridden.

A quick note on wiring

The feedback system is separated from the main track power in order to prevent interference - the feedback signals are carried back to the R, S terminals on the rear of the LZV200 (or LZV100) command station.  In order to keep interference down Lenz advise that you twist the pair of wires that go to the feedback bus.  The feedback wires should not be laid parallel to the track bus or live cables  - leave a couple of inches distance when channelling the feedback bus wires under the layout.  We use 6 amp rated wiring for the track power wiring so that this covers the 5 amp capacity of the system.

Notes on available PC Programmes:

Disclaimer: A& H Models is not affiliated with the following software products however they have had positive reviews so we would like to make Lenz customers aware of them.  The links below have contact details for the software publishers - Please make sure that your computer is compatible before making a purchase.  The software publishers will be able to assist with any questions you may have.

RailRoad & Co Traincontroller (Freiwald) - www.freiwald.com/pages/index.html

RocRail - https://wiki.rocrail.net/doku.php

Windigipet - www.windigipet.de/foren/index.php

iTrain - www.berros.eu/en/itrain/

JMRI - www.jmri.org/

11100 LS100 Accessory decoder for 4 turnouts with feedback
LENZ1110011100 LS100 Accessory decoder for 4 turnouts with feedback

Lenz 11100 LS100 Accessory decoder for 4 turnouts with feedback 
Accessory decoders are the link between your NMRA DCC system and your functional devices (that is turnouts, signals, uncouplers, etc.) on your model train layout.
Accessory decoders receive commands sent from the command station via the power station and activate the drives of turnouts or other switching devices. For DIGITAL plus systems these switching commands are activated from input devices, such as, hand held controller LH100 or LH90 (or in connection with another, compatible digital system).
Dimensions: approximately 3.5 x 3.5” (90 x 90 mm)

3 Amp Maximum 16 v AC Power input needed

LS100 Manual

A & H Help page for the LS100

11201 LR101 Feedback module with 8 outlets
LENZ1120111201 LR101 Feedback module with 8 outlets

Lenz 11201 LR101 Feedback module with 8 outlets

The most well known and commonly used form of feedback is information as to if a track on your model train layout is occupied or not. Even when you control your layout “only” by hand, you will surely want to know the status of tracks that can’t be seen. Hidden staging yards are referred to as “hidden” for a reason.

Feedback is absolutely necessary for fully or partially automated operation. How else will a computer program “see” if a particular track is free or not? This information is needed in order to know if a train may enter a particular track or not.

The feedback module LR101 has 8 inputs to connect switch contacts or occupancy detectors LB101 and 1 input to connect a voltage detector LB050.

To bridge unstable switch conditions (e.g. temporary interruptions of the power supply), each signal input can be assigned a programmable delay time for feedback on the occupancy status of a track. The status is reported to the command station LZV100 or LZV200 via the feedback bus. The status can be displayed with a manual control LH100 or LH101 or a PC (via the Digital plus interface).

11210 LB101 Occupancy module
LENZ1121011210 LB101 Occupancy module

Lenz 11210 LB101 Occupancy module

In order to detect the status of tracks the LB101 functions as a current sensor, and is inserted between the LR101 and the monitored track section. The LB101 can monitor two track sections independently from each other.

General information about the LB101 Dual Occupancy Detector:

The LB101 contains two independent occupancy detectors, each of which can be used to detect that a train or piece of rolling stock occupies a section of track. It operates on the so called “current sensing principle”. The LB101 only detects occupancy when there is a "current consumer" within the monitored track section (detection section). The LB101 has been designed to detect a decoder equipped locomotive or a single car with lighting or resistor wheelsets.

When the LB101 detects that there is something it its detection zone, the LB101 closes an electronic switch. This switch can be used to trigger layout feedback devices such as the DIGITAL plus LR101 encoder,
or other low current electronic inputs such as those used to trigger some signal systems. The LB101 is compatible with all NMRA DCC systems.

11220 LB050 Voltage detector for feedback module LR101
LENZ1122011220 LB050 Voltage detector for feedback module LR101

Lenz  11220 LB050 Voltage detector for feedback module LR101 

Status detection via current sensors, such as the occupancy detector LB101, has one crucial disadvantage: if the operating voltage is interrupted, so is the power supply. In this case, occupancy detection fails: the signal output will report unoccupied tracks that are, in fact, occupied. Power failures may be caused when the voltage is switched off or short circuits occur which are a frequent phenomenon in model railway systems. The voltage detector LB050 was designed to prevent faulty feedback. It checks whether digital voltage is applied to the track; if not, the present status will be fed back until voltage is reapplied.


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