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MAS Sequencer


The video shows a MAS Sequencer controlling a 4 aspect colour light signal. After passing the signal the train reaches the MAS Sequencer (located under the baseboard). As the MAS Sequencer's built in infra red detects the train it changes the signal to red. After the train has cleared the detector the MAS Sequencer starts timing.


There is a first timing interval at red followed by yellow then double yellow after which the signal returns to green. The timing is adjustable between 7 and 80 seconds.


If the signal is at yellow or double yellow when the train passes it still changes to red. There is information about how full size signals work in the signalling section of the web site. From this you will see that the MAS Sequencer is an easy way to get the same effect as a real signal.

As well as 4 aspect signals the MAS Sequencer gives easily installed automatic operation of 2 and 3 aspect signals.

You can determine whereabouts the signal changes to red by positioning the MAS Sequencer there.

The wiring is very simple. The wires from the power supply connect to terminals + and 0V and the wires from the signal connect to the terminals shown in the diagram.

There is no connection to the track so the MAS Sequencer works equally well with DC or DCC.

For a summary of all the units for controlling 3 and 4 aspect signals please see the 3 and 4 aspect signalling page.

Power supply

The MAS Sequencer can be powered from AC or DC, any Voltage between 12 and 16 Volts.

Wiring Signals to the MAS Sequencer

The MAS Sequencer works with LED signals. UK manufacturers (CR signals, Eckon, Bercko, Traintronics etc) wire their signals common negative. This means that the common wire (usually black) from the signal connects to all the cathode (negative) legs of the LEDs within the signal. European and American signals are usually common positive. Please specify which type of signal when ordering so that we can supply a compatible MAS Sequencer. We also need to know how many aspects (number of lights) your signals have.

The signal terminals have built in resistors. This means that LED signals can be connected directly to them. If the signals already have resistors attached then they will still work but will be dimmer. If they are not bright enough the resistors supplied with the signal can be safely removed.

Adjusting the timing

The device labelled pot on the diagram is a potentiometer. This is rotated with a small screwdriver to adjust the length of the timing sequence.

Override to red

If there is a junction or station then the signal may sometimes need to be set to red to stop a train. The RR terminal is provided for this. A switch or contact operated by a points movement is used to connect the RR terminal to the 0V terminal. Whilst these terminals are connected the signal will be at red.

Another use for the RR terminal is on bidirectional lines. When trains run in the opposite direction to that signaled the signal should be at red. If the control system is DC then the Train Direction Detector can be wired into the RR terminal. For DCC a switch can be used. A single switch may be connected to more than one MAS Sequencer or IRDASC-4 and if a SPDT switch (single pole double throw) is used, a single switch will work for controls in both directions.

More than one signal on a line

Wiring to control two colour light signals prototypically with passage movement of trains

When there is more than one signal along a line each signal could be controlled by its own MAS Sequencer. However this could result in the model signals showing combinations of lights that are not accurate. A better solution is to control the second signal from an IRDASC-4 board. When the train is detected by the IRDASC-4 the signal controlled by it turns to red. This signal stays at red until the train has cleared the MAS Sequencer then it will change to yellow. The correct sequence of signals as described in the signalling section will occur. Instead of controlling its signal with a timer the IRDASC-4 sets its signal according to the colour of the next signal up the line (MAS Sequencer). The purple wire between the S (send) terminal of the MAS Sequencer and the R (receive) terminal of the IRDASC-4 carries the information about what aspect (colour) the MAS Sequencer is at. Both boards share the same power supply. If there are more signals along the line extra IRDASC-4s can be used linking the S and R terminals between each. There is a web page with more information about IRDASC-4s. IRDASC-4RI, IRDASC-5 and IRDASC5RI can also be used with the MAS Sequencer.

Infra red detection

The MAS Sequencer can be supplied with extended wires to the infra red detection devices. These are twisted together to reduce electrical interference/

The MAS Sequencers have built in infra red train detection. This consists of an infra red emitter and infra red detector which are located in a hole in the baseboard and reflect an infra red beam off the underside of rolling stock. Advantages to infra red detection are that no modifications to the rolling stock are required and that it works equally well in the dark. The infra red emitter and detector are 22mm (3/4inch long). If the base boards are thicker than this or support beams are in the way the MAS Sequencer-EW can be used. The MAS Sequencer-EW has the infra red emitter and detector at the ends of 18 inch wires. A photograph of the MAS Sequencer-EW is shown below with the extended wires coiled:

To aid testing on installation there is a train detected LED mounted on the board. This lights when a train is detected by the infra red.

Dimensions of MAS Sequencer:

Length 135 mm 5.3 inches

Width 32 mm 1.25 inches