Servo Controller SRV1-NS

wiring the BLOCKsignalling SRV1-NS 

  • Detects trains using an infra-red sensor
  • Automatically operates an attached servo
  • Fully adjustable settings
  • Wide input voltage range

 

We were looking for a way to operate servos based on detecting trains, so for instance, when a train approaches a set of points, the points would automatically move to route the train.

It would also be great if the train could automatically trigger signals, or loco-shed doors, or operate a crane or water spout. 

With the SRV1-NS  any feature can be automated by the servo once triggered by the train.

If you are using Faller cars on you model layout, then these can also trigger the movement of features, such as a person crossing the road or a policeman waving on traffic.

To provide the maximum flexibility all the settings are adjustable so you can tailor the servo's actions to suit your needs.  To make thing even easier, we have added some presets to get you up an running with the minimum fuss for common requirements.

Finally, to make wiring as easy as possible, you can power the module from a range of power supply voltage, ensuring that you can power the module from virtually any supply on your layout, even the DCC track.

 

Servo Motors

Servo motors consist of a small dc motor and gearbox combination, designed to drive an externally mounted arm (horn) through a limited range of angles.  The motor operates at high speed, and the gearbox reduces the speed to a more appropriate level and so increases the torque significantly.  An in-built control circuit varies the motor direction and speed to allow the output shaft to turn to the desired position.

Servos are compact and easy to mount.  The attached points, barrier or gate can be directly attached to the servo by fixing a wire into the centre of the output shaft with epoxy, or a variety of horns can be mounted on to the output shaft and then extended with thin modelling wire to connect to gates, barriers and signals, etc.

The servos must be plugged in to the SRV1-NS with the correct orientation.  The signal wire (usually orange or white) must be closes to the centre of the module.  No damage will occur is the plugs are inserted in reverse.

The SRV1-NS is designed for operation with all types of miniature analogue servos.

 

Power Supply

The module operates from AC, DC or DCC (track bus) supplies.

You can use a DC power supply between 12V and 25V DC, or any AC power supply between 12V and 16V AC.

If using DCC, the feed can be between 12V and 25V, which covers all normal DCC layouts.  A DCC feed is not normally recommended, as this power is better used to drive trains.

A 12V DC supply from a dedicated adaptor is recommended.

The normal maximum current is approximately 200mA, but if the servo operates against a fixed object, the current can rise to 1A.

The power input is protected against reverse polarity.

Please check the wiring carefully before turning on the power to prevent damage to the module.

 

Factory Reset

By performing a factory reset, any changes which have been made to any settings will be returned to the standard factory defaults, with the Start position for each servo being approximately 45 degrees anticlockwise of the servo mid-position.  The stop position will be approximately 90 degrees clockwise of this position.

Note that servos will immediately move to their fully anticlockwise starting positions.

 

Built-in Programs

In order to set-up the module with minimum effort, there are several programs built-in.

Selecting one of these programs will perform a factory reset on the module (losing any previously made changes), and then make a number of setting adjustments automatically.

If you want to further refine the settings of these programs, follow the instructions in the following section after selecting the program.

 

Program 1 - Points Motor

When the infra-red sensor is triggered by a train, the module immediately activates the servo to turn 90 degrees clockwise at speed 8.

When the servo has reached the end of its travel, the module checks to see if the train has cleared the sensor.

If the train has cleared the sensor, the module waits 10 seconds, before the servo turns anticlockwise back to its starting position at speed 12.

The module then restarts and awaits the next train.

 

Program 2- Points Motor with proportion of trains sent to the branch

When the infra-red sensor is triggered by a train, the module decides whether to react to the train or to ignore it.

In this mode, a proportion of trains are sent to the branch line.  In this case  every fourth train is routed to the branch, the rest are ignored.

If this train is to be routed to the branch, activates the servo to turn 90 degrees clockwise at speed 8.

When the servo has reached the end of its travel, the module checks to see if the train has cleared the sensor.

If the train has cleared the sensor, the module waits 10 seconds, before the servo turns anticlockwise back to its starting position at speed 12.

The module then restarts and awaits the next train.

 

Program 3 -Points Motor with trains randomly sent to the branch

When the infra-red sensor is triggered by a train, the module decides whether to react to the train or to ignore it.

In this mode, a proportion of trains are sent to the branch line.  In this case 1 in every 4 trains are routed to the branch (selected randomly), the rest are ignored.

If this train is to be routed to the branch, activates the servo to turn 90 degrees clockwise at speed 8.

When the servo has reached the end of its travel, the module checks to see if the train has cleared the sensor.

If the train has cleared the sensor, the module waits 10 seconds, before the servo turns anticlockwise back to its starting position at speed 12.

The module then restarts and awaits the next train.

 

Program 4 - Semaphore Signal

This mode is ideal for connecting to a semaphore signal, such as those manufactured by Ratio and others.

When the infra-red sensor is triggered by a train, the module immediately activates the servo to turn 90 degrees clockwise at speed 8.

The movement has simulated bounce to mimic the action of a real signal.

The module waits 5 seconds, before the servo turns anticlockwise back to its starting position at speed 12.

The module then restarts and awaits the next train.

 

Program 5- Water Spout

This mode is ideal for a water spout by the side of a line, as the train needs to be stationary beside the spout for 12 seconds for the spout to be moved.

When the infra-red sensor is triggered by a train stationary over the sensor for at least 12 seconds, the module immediately activates the servo to turn 90 degrees clockwise at speed 4.

The module waits 20 seconds, before the servo turns anticlockwise back to its starting position at speed 4.

The module waits for the train to leave and then restarts and awaits the next stationary train.

 

Program 6 - Crane 1

This mode is ideal for a crane mounted by the side of a line, as the train needs to be stationary beside the crane for 12 seconds for the crane is operated.

When the infra-red sensor is triggered by a train stationary over the sensor for at least 12 seconds, the module immediately activates the servo to turn 90 degrees clockwise at speed 4.

The module operates the crane back and forth three times, with random waiting times.

The module waits for the train to leave and then restarts and awaits the next stationary train.

 

Program 7 - Crane 2

This mode is ideal for a crane mounted by the side of a line, as the train needs to be stationary beside the crane for 12 seconds for the crane to be operated.

In this mode, the crane will continue to operate, as long as the train is in place.

When the infra-red sensor is triggered by a train stationary over the sensor for at least 12 seconds, the module immediately activates the servo to turn 90 degrees clockwise at speed 4.

The module operates the crane back and forth once, with random waiting times between movements.

The module waits for the train to leave and then restarts and awaits the next stationary train.

 

 

Fine Tuning Settings

The programs above should give you a good idea of the options available.

If you wish to further tailor the operation of the module, then there are many options.  It is by no means necessary to understand this section, but it does illustrate all the options available if you have a special requirement.

The module works by making a number of decisions once it is triggered.  Each of these decisions can be altered by the user by reprogramming various settings.  These settings are all shown in the programming diagram at the end of this article.

The decision route taken by the module are shown in the diagram immediately below.

Whether the module is triggered or not by a passing train is based on the sensitivity setting for the infra-red sensor.  The sensitivity setting will not normally need adjustment, but it could be for instance to ignore carriages with dark undersides and only react to ones with white tape on the underside.

Once the module has detected the train, it needs to be present for short period of time for the module to confirm with certainty that it is present.  This is usually 1 second, over which the module repeatedly checks for the train.

Once the module has confirmed the true presence of the train, the module checks whether it should react.  There are three choices.  The module can be set to always react, or a proportion of trains trigger the module, or the module reacts randomly, the rest are ignored.  In the case of the proportion setting, the module keeps track of the number of triggerings, and only reacts to every 3rd, 4th, 5th train etc.  With the random setting, the module randomly choses whether to react.  Again, the module can be set to 1 in every 3,  1 in every 4, etc.

wiring the BLOCKsignalling SRV1-NS 

If the module is triggered as a result of this check, a delay can be set to occur before the first servo movement.  There are three options.  The options are no delay, a fixed delay, or a random delay.  The fixed delay is up to 255 seconds.  The random delay is calculated each time the module is triggered, and falls between 25% and 100% of the fixed delay set.

The servo then moves.

The servo start position, end position and speed of rotation can be set.

There are a number of places in the program where the module can be forced to wait for the sensor to be clear before moving on.  For instance, if the train stopped over the sensor in front of a set of points, you might not want the program to continue until the train has moved off.

There is now the possibility of another delay.  Again, there are three options.  The options are no delay, a fixed delay, or a random delay.  The fixed delay is up to 255 seconds.  The random delay is calculated each time the module is triggered, and falls between 25% and 100% of the fixed delay set.

The sensor can again be checked at this point to see if the sensor is clear.

Then the servo moves back to its start position. There is a separate speed setting for this movement.

Next, there is the option of another check for the sensor to be clear, another delay, and another check for the sensor to be clear.

If the operation of the servo needs to be occur several times, it can be repeated up to 255 times, following the same delays each time.

The module can also be set to:

always repeat if the sensor is obstructed
always repeat if the sensor is clear
never repeat if the sensor is obstructed
never repeat if the sensor is clear

Once the required number of operations has occured, there is the possibly to finally check the sensor is clear, before the module restarts.

 

 

Program Flow Diagram

Programming is performed by holding down the Push Button when switching on the power.

The red led on the PCB flashes at 1 second intervals.  When the required number of flashes is seen (see later for the list of possible choices) the button is released to store the first value. At this point the led comes on for five seconds to confirm the value is stored.

The led then starts flashing again, and this time the button needs to be pressed to store the second value.

Once the two values to be stored are entered, the led flashes 10 times rapidly, and the module starts operating.

If the programming is aborted by switching off, then the programming must be repeated.

 

 

Product due May 2016.