Helvest AB400 FleX Layout Module User Manual
- June 9, 2024
- Helvest
Table of Contents
AB400 FleX Layout Module
User Manual
General product presentation
1.1 AB400 train detection feedback module
The AB400 board is a module that detects the location of trains on up to 4
sections of track, using current-absorption technology: this means that it
detects where the train is based on where, on the track, it picks up current.
This is a layout module for the HP100 motherboard. It must be plugged into the
‘layout’ connectors of the HP100 board and is automatically recognised by it.
To insert the module, switch off the HP100 board’s power supply, ensure that
the connectors are aligned, and apply light pressure until the module is fully
inserted into the slot.
1.2 Preparation of sections
In order to identify whether the train is on a certain track or in a certain
position, the corresponding tracks must first be electrically separated.
To section the tracks, proceed as follows: 
- Conventional “two-rail” power supply: interrupt only one of the two rails, either by using insulated joints, or simply by cutting so that the rail sections are electrically insulated (figure 1A).
- “Three-rail” supply systems: with appropriate insulation ( red in the drawing) interrupt the central conductor in the sections of interest (figure 1B)
1.3 Electrical connections
All the following operations must be performed with the power switched off.
The HP100 motherboard must be powered with any voltage from 7 to 20V AC, or 7
to 16V DC. A digital bus such as DCC is also suitable, although for large
layouts this is not recommended (fig. 2)
A ‘net’ module suitable for data transmission must be mounted on the HP100, such as the MVnet MV100 module or other modules that will be available in the future.
Fig. 3 shows the AB400 connectors in detail. In connector (1), indicated with
COM, must be inserted the wire common to all sections, coming from the booster
or the digital control unit. In figure 2 this wire is shown in black.
Connector (2) has the contacts for the four block sections, numbered 1 to 4:
these wires must go to the sectioned rails, also shown 1 to 4 in figure 2.
The unsectioned rail ( marked with the red wire in fig. 2) is to be connected
directly to the control unit or booster.
The track sections where presence is to be detected can be either digital or
analogue.
After connecting the tracks as in fig.2, before setting up the board on MVnet,
power up the decoder and the layout and run a train on the connected block
sections. The yellow LEDs in positions 3 and 4 light up as the train runs.
WARNING: It is imperative to connect on the same AB400 module wires
coming from the same control unit, or the same booster.
Connecting wires from different control units, or from different boosters, on
the same AB400 module may damage the control unit or the booster itself. This
rule of not connecting different digital sources together applies to any
connection, even without presence detection modules.
1.4 Mounting the board on the layout
ANext to the AB400 module, any other layout module can be installed: e.g. a
module for switches, for signals, a second AB400 module to control a total of
8 sections, etc. The complete board must be mounted so that it does NOT touch
any element during operation. In particular, it must not come into contact
with any metal material.
For temporary installations, it can be placed on a non-flammable insulating
surface (plastic, glass, ceramic floor, etc.).
For fixed layouts, it is recommended to
mount it by screwing the HP100 onto a wooden surface with the screws and
spacers provided. (figure). This must be done before inserting the AB400
module (if additional boards have already been inserted, they can be removed
gently without any problems).
BOARD OPERATION
2.1 Normal operation
Once all connections have been made, power the board. The green LED no. (5)
(fig. 3) indicates that the power supply is correct.
The LEDs at positions no. (3) and (4), numbered 1 to 4, indicate the presence
in the 4 sections of the board. If there are no locomotives or vehicles
drawing current, the lights must be switched off.
By placing a locomotive or a current-consuming vehicle (such as an illuminated
car, a car with tail lights, etc.) on the corresponding track section, the LED
lights up. Train presence data is sent to the network via the MVnet module.
This data can be processed by the computer or other boards as required.
2.2 Current flow and protection
Each section holds a maximum absorption of 2A, which is plenty for common
model railway applications.
In the event of a short circuit, the control unit itself or the power supply
unit takes care of disconnecting the current.
WARNING: Never power the track with devices that are not short-circuit
protected! This rule is independent of the use of the AB400 module.
In any system, supplying power to the track with non-short-circuit-protected
devices can seriously damage your rolling stock and all connected equipment,
as well as present a fire risk.
2.3 Train detection
These sensors operate in both analogue and digital mode, and detect the
presence of the train in real time on the relevant section by noticing if a
device is drawing current on that section: a locomotive engine or its lights,
or simply the decoder if the locomotive is digital. In digital operation, the
decoder is detected even if no other devices are active (so even a stationary
locomotive with its lights off).
Passenger cars or freight wagons are detected if they are equipped with
something that draws current, such as tail lights, interior lighting, or a
decoder.
In the event of problems, such as some vehicles becoming uncoupled while
running or if the locomotive stops due to a lack of electrical contact, it is
important that the situation is also detected by the sensors.
For this reason, it is advisable to always protect both ends of the train, so
that the tail vehicle, if it is not illuminated or does not have its lights
on, is also detected.
For this purpose, it is sufficient to equip the tail vehicle with a resistor on one axle, which makes contact between the two wheels (fig. 5). We recommend a resistor value of around 5 kΩ. In this way, there is minimal current draw at both ends of the train in any situation, and the train is protected at both ends, the locomotive motor (M) on one side and the resistor (R) on the other (fig. 6).
For three-rail systems, it is not possible to take over the last car with an arrangement as described in fig. 5. The last car must be equipped with a pickup shoe and some device that draws current (tail lights, decoder, interior lighting, etc.).
Troubleshooting
To solve power supply/connection issues etc., see motherboard troubleshooting.
| Problem | Possible causes |
|---|
The module is switched on but does not respond, and the power LEDs remain
off.| If the HP100 board is powered (green LED on HP100 is on), the module is
incorrectly inserted. Check for correct insertion.
The board is in contact with metal parts.
The module is switched on, the power LEDs are on, but the trains in the
corresponding sections do not move.| Check the correct connection of the block
sections, which must be done as in figure 2.
Check that the wires make correct contact in the terminals (they have been
stripped well and the screws are tight).
Check that the track contacts are clean.
If there is a short-circuit: Make sure that you have not mixed wires from
different control panels or boosters on the same AB400.
The module is switched on, the power LEDs are lit, the trains in the
corresponding sections move, but the yellow LEDs registering presence do not
light up.| Check the correct connection of the block sections, which must be
done as in figure 2.
TECHNICAL SPECIFICATIONS
Board type:| track occupancy detection module with current absorption
technology for HP100 motherboard
---|---
Input power supply for
logic circuit: 5| 5V DC, supplied by motherboard
Signalling LEDs:| voltage presence, occupancy of block sections.
Working temperature:| 0 °C – 40 °C
Dimensions| 80 x 35 mm
Firmware HP100| >4.0
User Manual rev. 1.0 (2023).
All rights reserved. Copying, even in part, of the contents of this manual is
only permitted with the express written permission of the manufacturer.
“Helvest” is a registered trademark owned by Helvest Systems GmbH, Fribourg (CH).
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