Model Train Technology PRECISION DETECTOR Trackside User manual

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MTT PRECISION DETECTOR™ -Trackside
1mm precision up to 150mm
OPERATIONS MANUAL
Version 1.1a
Works with Z, N, HO and O Scale

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The Model Train Technology™ PRECISION DETECTOR™ – Trackside is
designed to provide an adjustable, multifaceted way to detect trains on
one or more parallel tracks with the least amount of work to install and
operate. At last, there is no need to adjust or calibrate anything for
changing or difficult light conditions. The detector is housed inside an
3D printed electrical box that is mounted from the top of the layout.
We think this is easier than banging around under the layout to install
brackets and drill holes. It’s also more prototypical because the real
track detection of modern railroad IS housed inside electrical boxes
along the trackside. We provide two types of base mounts, one with

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holes for screws or glue and a minimally sized base that matches the
footprint of the top box. The PRECISION DETECTOR™ slides into the
base bracket and then the box top slides over the top of that.
After we had our share of frustration with IR (infrared) detectors that
are susceptible to ambient light, particularly florescent, some LEDs and
mercury bulbs found at large train shows, we searched for a smaller,
faster, more precise technology that would also be impervious to poor
light conditions. The sensor we chose, along with our software, will
detect the location of a train car anywhere within a 150mm (5.5”) range
with 1mm precision without regard to lighting conditions.
This means you can put the sensor near the track, or you can hide it
away in a nearby building or in the side of a hill. You can also use the
PRECISION DETECTOR™ to alert when a train has reached the endpoint
of track inside a hidden yard. In other words, aimed down the track
from the endpoint, not across it. In this example the detector will only
“see” the train on the track its’ aim down – and not the adjacent track.
Summary of Features:
• Long, precise sensor range (1mm up to 150mm)
• No more adjusting for varying light conditions.
• Adjustable detect ranges (N & HO and O gauge)
• Detect one parallel track and ignore the others
• Adjustable time-out (0-60 seconds)
• Reversable Signal output (INVERT)
• Two mounting options plus Electrical box integrated design

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• Includes a 2mm screwdriver.
The board is powered with a 5V DC supply. To make sure all the
detection works properly we designed a low cost 5V Power Center
Module which also makes it easy to connect things up.
Yellow Signal Wire
(OPEN DRAIN TO GND)
5VDC
DIP SWITCHES
Timeout Adjust
Indicator LED
Light
Range Adjust

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The detector can be set to detect an adjustable Wide Range from 5mm
up to 150mm – or anything smaller than that as you chose. In this first
example, anything within the range you set beginning at 5mm - will
trigger the detector.
The second mode allows you to select a narrow sub-range anywhere
within the 5-150mm range. If you select N Scale (via the DIP switches)
the detection range will be 10m WIDE and that 10mm range can be
“placed” anywhere inside the 5 to 150mm range. Anything closer or
further will not be detected.
Detection Range Width:
N Scale 10mm
HO scale 15mm
O/S Scale 30mm
All you do is set the dip switches on the board to your scale and adjust
the location of the sensor to meet your specific needs.
In addition, there is a second trim potentiometer (trim pot) that allows
you adjust how long the trigger stays “tripped” after the detector is
clear. We provide a 2mm screwdriver for adjusting this. ( I can’t tell
you how many times I needed a small screwdriver for this kind of thing
and could not find it and didn’t want to buy another jewelers kit.) To
make it easy as possible, we include one with the detector. If you buy a
lot of detectors you can return the extra screwdrivers. We will reuse
them.

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The default setting with the trim pot adjusted all the way to the left
(counterclockwise) is under 1 second. With the dial all the way to the
right (clockwise) the timeout period is either 30 seconds or 60 seconds
depending on the timeout DIP setting.
If you are using the PRECISION DETECTOR™ with our MTT Signal
Controller you will most likely want to leave the setting to 1 second and
let the Signal Controller manage the timing. If you are using our Sound
Module, then use the PRECISION DETECTOR™ timing to adjust when to
stop a sound after the train has passed. An example would be a
crossing bell sound. With our Fiber Lighting Controller and a gate
crossing use the PRECISION DETECTOR™ to set the timeout so the lights
and sound stop at the same time.
The PRECISION DETECTOR™ provides a DIGITAL signal output (LOW)
which is the kind used by most model railroad electronic controls that
you would normally hook up such as sound modules, Light Controllers
(like our Fiber and LED Controllers) and Block Signal Controllers. This
detector can be configured to switch a relay that has a digital input
option, but it cannot power or switch the relay itself. (see the example
at the end on how to connect a relay)
Once installed on the layout, the supplied electrical box cover is
designed to protect and hide the electronics. We recommend using
Gem-Tack® glue to fasten the mounting plate to the layout surface. The
advantage of using this particular white glue is that you can remove it if
you need to. Don’t use “super glue".

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On the board is a blue indicator LED. This will flash four times when
power is first turned on and thereafter will light when the detector is
triggered. (INVERT mode will have the light ON when not triggered and
OFF when triggered)
INSTALLATION and TESTING
The default setting (via DIP switches) is to detect the Wide Range from
5mm to 150mm. Anything in this range will trip the detector. We
recommend you start with this for testing purposes.
Connect the black power wires to your 5 DC power source. There is no
polarity required. With power ON you can place your hand in front of
the sensor and the blue LED should light and go off when you move
away.
To shorten the detect range, turn the left-hand trim pot to the left
(counterclockwise). With the slot of the trip pot showing vertical the
detect distance is about 65mm. Test this by moving your hand, or
some object, from outside the 150mm range to closer until the blue
light goes on. In this mode, anything from 5mm away from the sensor
to 65mm will trip the detector.
Next, using the provided screwdriver, turn the right-hand trim pot to
the right about ¼ turn (or 15 minutes’ worth if you want to use a clock
metaphor). Then wave your hand in front of the sensor and then away.
The LED should stay lit for about 7-10 seconds. This demonstrates the
delayed timeout aspect of the detector.

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Turn the timeout back all the way to the left (1 second) during the
following testing and experimentation. It is easier to change the
detector settings when the timeout setting is zero. It just helps speed
things up to follow what’s going on instead of waiting for the time out.
The MTT PRECISION DETECTOR™ has an accuracy to 1mm. That allows
it to detect the exact rail space of N, HO or O Scale track. In the
example below we used the DIP switches to set the scale to N Scale
which gives us a 10mm “zone”. Then we place the detector within
150mm of the furthest rail of the track we want to detect. Then you
adjust the range so that the blue indicator light goes on at the closest
edge of the zone. (indicated by the red line). The procedure to do this
is:
1. For N Scale, set DIP#1 ON, DIP#2 OFF (#3 and #4 should be OFF)
2. Place any car on the track you want to detect at the detection
location you want. (we’ll assume you have placed the PRECISION
DETECTOR™ where you want it. You can tape it down to the
layout temporarily to test things out.
3. Turn the Range trip pot all the way to the right.
4. Turn the Range trim pot slowly to the left (counterclockwise) until
the blue light goes on. You might have to very finely tune the trim
pot to get the range where you want it. Once set you will not have
to adjust it again. Ever.

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5. Test by moving the car in and out of the sight of the detector. The
Blue indicator should go on and off. Move the car out of sight.
Place you hand or an object between the detector and the track.
Nothing should happen since it is not within the 10mm range that
you set – which should be directly over the rails of the track.

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Keep in mind that the trim pot rotation is 300 degrees and that allows
adjustment over 145mm. When you are adjusting the range in N Scale
it only takes a small amount of rotation to move 10mm.
The Yellow Signal wire can now be connected to the controller device
of your choice. The signal protocol is called OPEN DRAIN (LOW). This
simply means that the device will work with control units that are
looking for a connection to GROUND through the signal wire.
HOWEVER, the detector must have a way to connect back to a source
of ground. The most bullet proof way to do that is to have the
controlling device and the detector powered by the same power
supply. Then naturally they will share a common ground through the
power supply, and everything will work fine.
Our Fiber Lighting Controller™ has a built-in 5V power supply output
that is designed to connect to this detector. In that case, you only need
the one Yellow signal wire back to the detection side of the Lighting
Controller.
Although not recommended, you may want to use a separate power
supply for the detectors and for your controller. In this situation you
can connect the 3RD solder pad (GROUND) on the PRECISION
DETECTOR™ to the GROUND on the controlling unit you are connecting
to.
MAKE SURE YOU ARE CONNECTING GROUND AND NOT PLUS(+)

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We did not supply a wire for this purpose because this is uncommon
and usually not necessary, but the connection is there if you need it. By
connecting the two grounds together, the YELLOW signal wire now has
a path to GROUND to complete the OPEN DRAIN (to ground) circuit.
INVERTED SIGNAL
An INVERTED SIGNAL simply means that the PRECISION DETECTOR™
will send an ON signal when the sensor is OFF, and visa versa. You can
tell this is the case if the blue LED is always on but turns OFF when you
place your hand in front of the sensor. Why would you use this? You
can use this when you are connection to a block signal system or more
likely if you are using our MTT Sound Module. You can have ambient
background noises going while the train is away and then have them
turn off as the train (with sound) passes or pulls into the station.
To change the Signal out to INVERT, change the right most DIP switch to
ON (up position).
NOTE: Whenever you change any of the DIP switches the PRECISION
DETECTOR™ detects that change and updates its operation
automatically. It takes two seconds to update on a DIP switch change.

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TRIGGER TIMEOUT SETTINGS
Rotate the trim pot (variable resistor) clockwise to increase the length
of the detector timeout. There are two ranges: 0-30 and 31-60
seconds. You change to the 31-60 second range by turning DIP switch
#3 ON.
INVERT switch #4
shown in the UP
(ON) position
The Timeout switch #3
shown in the OFF
position, so the timeout
range is 0-30 seconds

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The PRECISION DETECTOR™ – Trackside is very fast and very precise to
the point that it can detect the space between cars when a train is
moving slowly. To avoid the sensor going off in this situation, adjust
the timeout just a little above the time that it takes a car with the
biggest gap to cover the detection area. Usually 1-2 seconds is all that’s
needed.
Horizontal Installation
For certain N Scale situations, the height of the detector may place it
above the top gunnel of an empty gondola car or flat car. This isn’t and
issue for HO and O/S scale. The height of the track, rails, roadbed and
scenery where you plan to mount the detector all affect the targeting
beam of the sensor. To accommodate a lower train target, the
PRECISION DETECTOR™ – Trackside can be mounted horizontally (as
shown below) and the function will be the same. We recommend that
you place the sensor closer to the track instead of its max distance. The
reason is that lower placement horizontally the track itself will occupy
some of the sensor’s vision and thus may cause occasional false
readings.
You can select the horizontal version of the bracket and electrical box
at time of order. Everything else operates the same.

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On the next few pages are graphics to depict how the track detection
system works and the various range distances. These guidelines from
which you will need to fine tune for your particular layout, scale and
train car situation.
There is one option that we decided to leave intact, but it has an
operating flaw – based on physics and not the software. In the case
where you select to detect only the Far track between two parallel
tracks, be aware that if a train on the Near track comes along and
BLOCKs the detector from seeing the Far track, well of course both the
NEAR track AND the Far track will not detect.

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