BLOCKsignalling SEC4A-DCC User manual

SECTION CONTROLLERS
SEC4A-DCC & SEC4B-DCC
The BLOCKsignalling Section Control Module is designed for DCC layouts, to
protect a section of track to prevent more than one train entering that section at one
time.
Monitors trains entering and leaving a section of track
Automatically sets the signal at the start of the section to danger (red)
Switches a section of track from DCC to DC, so DCC equipped locos
automatically decelerate to a standstill in front of the signal at danger.
Communicates to previous sections to ensure they show yellow (and double
yellow) aspects when 3- and 4-aspect signals are used
Last section can simulate returning back to green using timers to provide
realistic operation when 3- and 4-aspect signals are used
Points which are not set in the trains favour can force the signal to danger and
switch the isolating section to DC
Signal can be forced to danger by an external input (useful for starter signals)
Suitable for 2-, 3-, and 4-aspect led signals (SEC4A-DCC for common-
cathode and SEC4B-DCC for common-anode signals)
Bidirectional running mode with 2-aspect signalling at each end of the line
New: Additional Station Stop Modes
New: Additional Dapol output
Remembers whether the section is occupied after the power is removed and
automatically restores the signals after power returns.
Simple to setup, but also fully configurable to provide the most realistic
operation
Requires a 12V DC Power Supply
BLOCKsignalling
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Introduction
The BLOCKsignalling Section Control Module is designed to protect a section of
track to prevent more than one train entering that section at one time (see later for
details of the Station Stop Modes).
At the entrance to the section there is a signal and a short isolated piece of track
which can be energised with DCC or DC by a relay and diode rectifier built-in to the
module. There is also an infra-red sensor (sensor 1) which is located below the
track which is able to detect trains passing the signal.
The isolated section of track is normally energised with DCC and the signal normally
shows a green aspect.
At the start of the section, the infra-red sensor is continuously looking for a trains
passing, and as soon as it detects one, it switches the signal to red and feeds DC to
the isolated section of track, slowing any approaching train to a standstill in front of
the red signal (see later for bidirectional running). In order for this to function
correctly, the loco needs to be configured to “Stop on DC”(see later for details of
how to configure this).
The module then uses a second infra-red sensor (sensor 2) located at the exit from
the section of track to detect when the train has completely left the section.
When this is confirmed, the signal at the entrance to the block is switched from
danger back to green (if a 2-aspect signal is used).
If 3- or 4-aspect signals are connected, then information from the following blocks is
used to switch the signal to show yellow or double yellow.
In 2-aspect mode, a Dapol signal can be driven via a relay connected to CH5 for
some of the modes (2, 7 and 8). This is discussed in further detail later.
The isolated track section at the entrance is also re-energised with DCC and any
waiting train will then accelerate away past the signal.

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Bidirectional Running
There are two additional programs for bi-directional running with 2-aspect signals.
The first uses both sensors to detect trains entering the section (one at each end).
When a train enters, the signal outputs are set to red. The sensors are checked
alternately.
When the train has completely entered, the module then begins checking both
sensors to see if a train leaves the section.
The sensors are checked alternately, and if a train is detected, the module waits until
the train has cleared that sensor before setting the signals to green.
The second mode for bi-directional running uses both sensors to detect trains
entering the section. When a train enters, the signal outputs are set to red.
The module remembers the entry sensor and then begins checking the other sensor
to see if a train leaves the section.
If a train is detected leaving via the exit sensor, the module waits until the train has
cleared that sensor before setting the signals to green.
In these two modes, the isolated track sections are not used.

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Loco Decoder Configuration
The module switches DC to the isolated section of track to slow and stop the loco.
If CV29 is programmed to prevent running on DC (bit 2 is set to 0), then the loco
decoder sees the presence of DC on the track as incorrect and so slows the loco to
a standstill at a rate set by CV4.
When DCC is restored to the isolated section, the loco decoder sees this and
accelerates away at a rate governed by CV5.
Please refer to your DCC decoder documentation if you are unsure about how to set
these settings. There is further information in the Troubleshooting section at the
end of this document that may help.
Power-Off Memory
There is a new setting to record whether there was a train in the section at the time
the power is turned off. When the power it turned on again, the information will be
reloaded from memory and so the correct status will be indicated on the signals and
relayed to any interconnected modules.
This feature is also used to remember the direction train was running when the
bidirectional mode is used.
This feature is disabled by default.

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Module Connections
The diagram below shows the connections to the module.
Terminals
Function
ACIN/+, ACIN/-
12V DC Power supply input
S
Track suppression connection
NC
Relay contact: Normally Closed
COM
Relay contact: Common
NO
Relay contact: Normally Open
SIG+,GND
Connection to previous block for interlocking (note 1)
A1,K1,C1,E1
Sensor 1 connections
CH1-CH5,VOUT
Connections for led signals
A2,K2,C2,E2
Sensor 2 connections
A+,K-
Connection to next block for interlocking (note 2)
Note 1: the connection between the modules carries coded information about the
presence of trains in this section (and following sections if appropriate). This
information is used to switch the yellow aspects on the signals (3- and 4-aspect
only).
Note 2: Optionally connecting steady 12V DC to this input, tells the module the next
section is occupied.
BLOCK
signalling
CH3 CH2 CH1 VOUT
COM NO S NC AC/IN+ AC/IN-
A2
K2
C2
E2
A+
K-
SENSOR 2
CONNECTIONS
LED SIGNAL
CONNECTIONS
SUPPLY RELAY CONTACTS
www.blocksignalling.co.uk
CH5 CH5
A1
K1
C1
E1
SIG+
GND
SENSOR 1
CONNECTIONS
IN FROM
NEXT BLOCK
OUT TO
PREVIOUS BLOCK
POWER
TRACK SUPRESSOR

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Power Supply
The controller is designed for use with a 12V DC plug-top type power supply.
The current consumption is 0.25A, and a power supply rated at 0.5A to 1A is
recommended.
Do not connect to the auxiliary terminals on the back of a train controller as the
module may operate unpredictably and could be damaged. These outputs are often
unsuitable as they are designated as a fairly basic power outputs for accessories
such as points motors and may not be smooth or stable.
If a DC power supply is connected with incorrect polarity no damage will occur, but
the module will not operate.

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Connection for a Single Block
The control of one block section consists of the following parts:
1. An entry sensor, to detect a train entering the section (sensor 1).
2. An exit sensor, to detect a train leaving the section (sensor 2).
3. A section of isolated track preceding the signal (there is a track break in only the
right-hand rail), which is controlled by a relay on the module to slow and stop a train
at the signal when the signal is at danger (this is not used with bidirectional running).
4. Connections to and from adjacent sections to communicate information about
which blocks are occupied (not required when 2-aspect signals are used).
5. A small vehicle bulb protects against short circuits across track breaks in the event
of any wiring errors when connecting up.
The following diagram shows the connections when 2-aspect signals are used.
TRACK
BREAK
BLOCK
signalling
ISOLATED SECTION
(RIGHT RAIL ONLY)
DCC BUS
TRACK
BREAK
DCC BUS
SECTION
ENTRY
DETECTOR
SECTION
EXIT
DETECTOR
DCC/ DC NEGATIVE
DCC
CONTROL
STATION
DCC
12V 10W LAMP
SEE TEXT NC SCOM

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If bidirectional running is being used with 2-aspect signals, then both the signals are
controlled by one module.
If 3- or 4-aspect signals are used, additional connections are required between the
modules to communicate which sections in front of the train are occupied, otherwise
the yellow aspects will not be shown on the signals.
BLOCK
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DCC BUS
DCC BUS
SENSOR1 SENSOR 2
DCC
CONTROL
STATION
DCC
TRACK
BREAK
TO PREVIOUS
BLOCK
(ONLY REQUIRED
FOR 3- & 4-ASPECT)
BLOCK
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ISOLATED SECTION
(RIGHT RAIL ONLY)
DCC BUS
TRACK
BREAK
DCC BUS
SECTION
ENTRY
DETECTOR
SECTION
EXIT
DETECTOR
DCC/ DC NEGATIVE
DCC
CONTROL
STATION
DCC
FROM FOLLOWING BLOCK
(ONLY REQUIRED FOR 3- &
4-ASPECT)
12V 10W LAMP
SEE TEXT NC SCOM

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Connection Multiple Simple Blocks
When 2-aspect signals are used, there are no interconnections between adjacent
sections (except the DCC bus).

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When 3- and 4-aspect signals are used, the Train in Section (TIS) wiring must be
linked from one block to the next, otherwise the yellow led on the signals will not
operate.

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2-Aspect Led Signal Example
In the following example, 2 aspect light signals are used. The train has driven from
the left to the right, and is currently in Block 3.
The block section controller for Block 3 has detected the train enter the section, and
has set the signal to danger (red) and switched DC to the track section to prevent
any other trains entering.
The auxiliary contacts on the points indicate to the controller of Block 4 that a route is
not available (12V appears on the inputs to the block 4 controller via the points motor
auxiliary contacts), and so it indicates danger and switches DC its track section.

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3 Aspect Light Signal Example
In the following example, 3 aspect light signals are used. The train has driven from
the left to the right, and is currently in Block 3.
The block section controller for Block 3 has detected the train enter the section, and
has set the signal to danger (red) and switched DC to the track section to prevent
any other trains entering.
The Block 3 controller signals to the preceding Block 2 controller that it is at danger
(red) and so the Block 2 controller indicates caution (yellow).
The auxiliary contacts on the points indicate to the controller of Block 4 that a route is
not available, and so it indicates danger and switches DC its track section.

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4 Aspect Light Signal Example
In the following example, 4 aspect light signals are used. The train has driven from
the left to the right, and is currently in Block 3.
The block section controller for Block 3 has detected the train enter the section, and
has set the signal to danger (red) and switched DC to the track section to prevent
any other trains entering.
The Block 3 controller signals to the preceding Block 2 controller that it is at danger
(red) and so the Block 2 controller indicates caution (yellow).
The Block 2 controller signals to the preceding Block 1 controller that it is at caution
(yellow) and so the Block 1 controller indicates caution (double yellow).
The auxiliary contacts on the points indicate to the controller of Block 4 that a route is
not available, and so it indicates danger and switches DC its track section.

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Configuration for Ends of Track and Points
At the start of a section of track, there are no preceding sections which are signalled,
so the connections of the module do not need to be connected to any preceding
blocks.
At the end of a section of track there are no following sections which are signalled,
so the connections of the module do not need to be connected to any following
blocks. When the train leaves the final block, the connected signal will switch from
red straight back to green.
As an option, these final blocks can be set to revert from red to green (via yellow and
double yellow if appropriate) by setting timers. For instance, a train can disappear
into a tunnel, and after a time, the signal will switch back through the sequence to
green automatically to give the most realistic operation.
The final module needs to be programmed to act using timers using memory 3 (see
later) and sensor 1 and sensor 2 need to be installed as normal.
Using auxiliary contacts from points motors, a 12V DC feed can be connected to the
A+, K- inputs of a module. A constant +12V DC will force the module to show a
danger signal and switch DC to a track section, protecting points which are not set in
a train's favour.

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Programming Procedure
Many of the settings on the module are adjustable (although for most users it is only
necessary to set whether 2-, 3- or 4-aspect signalling is used).
Programming is performed by inserting a link between the A and K terminals and
holding down the Push Button when switching on the power (this link will be removed
shortly and the infra-red sensor connected). The module can also be programmed
whilst the infra-red sensors are connected.
Full details of the programming procedure is given later in the document.

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Connecting the Infra-Red Sensors
An Infra-Red source and Infra-Red detector are moulded into a single 5mm x 6.5mm
package that can be located below the track bed to reflect light off rolling stock.
The wires can be extended using small chocolate block and extra lengths of cable if
required (not supplied).
BLOCK
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SENSOR REAR VIEW
EMITTERDETECTOR
MOULDING
CHAMFER
C
E K
ACONNECT TO ACONNECT TO C
CONNECT E CONNECT TO K
A
K
CE
Clear Lens
Grey Lens

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Sensitivity Setting
The module is supplied with the sensitivity pre-set to suit most installations and
should not need adjustment.
In locations such as tunnels, or when the module is not being used under the track
bed, then it may be desirable to adjust the detection threshold.
The sensitivity is factory set to 5, and can be adjusted from 1 to 10 (with 1 being the
most sensitive and 10 being the least sensitive).
To change the sensitivity, switch off the power to the module and hold down the
Push Button. Apply the power and continue holding the Push Button until 9 flashes
of the led are seen. At this point, release the button. You will see a long flash of five
seconds.
The led will begin flashing again. When you have reached the desired number of
flashes to set the new sensitivity, press the button. You will see a long flash of five
seconds and then 10 rapid flashes. The programming is then complete and the
module will restart. If you make a mistake programming, simply repeat the process.
Performing a factory reset will reset the sensitivity setting back to 5.

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Installation
The Infra-Red sensor is normally installed below the track-bed. The detection range
of the unit is up to approximately 25mm from the face of the package when normal
sensitivity is set (for dark surfaces with low levels of reflectivity).
The detector can be mounted in an 8mm hole drilled through the track baseboard. If
required, the detector can be held in place using a small amount of blutack,
expanded polystyrene or similar.
The led diameter is 2.2mm, so on smaller scales the leds can still have a clear view
between the sleepers.
BLOCK
signalling
Sensors Mounted
Through Baseboard
Isolated Section
(Length as required)
Track Break
Signal Position
(after track break)
Entry Sensor
Position
Minimum > Loco Length
Exit Sensor
Position
Position entry sensor at least one loco length past the
track break.
Position exit sensor so the whole train can leave the
section and so clear the sensor successfully.

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Led Connection
When using leds it is important to connect them the right way around.
The negative lead (cathode) is identified by a flat on the side of the led body, and by
having a shorter lead.

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Signal Wiring
This section controller comes in both a common-cathode (SEC4A-DCC) and a
common-anode version (SEC4B-DCC).
The following diagram shows the signal wiring for the two versions.