Model Train Technology MTT PRECISION DETECTOR User manual

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MTT PRECISION DETECTOR™ -Trackside
1mm precision up to 150mm
OPERATIONS MANUAL
Version 4.2a
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
and precise 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 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 in the track. 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 holes for
screws or glue, or a minimally sized base that matches the
footprint of the electrical box cover. The PRECISION
DETECTOR™ sensor board slides into the base bracket and then
the box top slides over 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

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(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)
• Auto-calibration mode for precise range setting
• Detect one parallel track and ignore the others
• Adjustable time-out (0-60 seconds)
• Reversable Signal output (INVERT)
• Two mounting options
• Electrical box integrated design
• Includes a 2mm screwdriver.

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HO PRECISION DETECTOR™ sensor board
Yellow Signal Wire
(OPEN DRAIN TO GND)
12VDC
SELECT button
SWITCHES
Timeout Adjust
Indicator LED
Range Adjust

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N Scale PRECISION DETECTOR™ sensor board
Range Adjust
Indicator LED
Light
Timeout Adjust
SELECT button
12VDC
Yellow Signal Wire
(OPEN DRAIN TO GND)

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The board can be powered with a 12VDC supply which is what
the MTT Power Module outputs. To make sure all the
detection works properly we designed a low-cost Power Center
Module that comes with a power supply.
To operate properly the Signal Controller and the Precision
Detector must be connected to the same power source.
A single push button has replaced the DIP switch. This makes it
easier to set the configuration settings and you don’t need
glasses! Simply press the SELECT button according to this chart:
The detector can be set to detect an adjustable Wide Range
from 5mm up to 150mm. Anything within the range you set
beginning at 5mm - will trigger the detector.

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The second mode allows you to select a narrow sub-range
anywhere within the 5-150mm range. If you select N Scale 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/O/S scale 15mm
All you do is push the SELECT button to fit 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 jeweler’s kit.) If you buy a lot of
detectors, you can return the extra screwdrivers. We will reuse
them.
The default setting with the trim pot adjusted all the way to the
left (counterclockwise) is under 1 second. With the dial

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adjusted all the way to the right (clockwise) the timeout period
is either 30 seconds or 60 seconds depending on the timeout
option selected via the pushbutton.
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 many 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

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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".
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)
The Precision Detector software has been updated to include
a new feature called Auto Calibrate. This make setting the
exact distance for detection to a rail car extremely simple.
STEPS:
1. To activate the saved calibration, the trim pot for ranging
must be set to zero. Turn the trim pot with the
screwdriver all the way to the left (counterclockwise).
The trim pot for the HO sensor is on the left and for N
scale it is the lower of the two.
2. If this is the first time to use calibration, the saved setting
may also be zero.

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3. Press and hold the select button on the sensor. If your
finger sets off the sensor (blue light), don’t worry. While
you continue to hold the select button the blue light will
go off. Hold the button for about 8 seconds and then the
blue light will come back on. When the light comes back
on, release the button.
4. The LED will blink 10 times, once per second, to allow you
time to slide the sensor back into its bracket (NO COVER
YET) and place a train car on the track in front of the
sensor you wish to calibrate.
5. After 10 seconds (10 blinks) there will be a 1 second
pause and then the LED will blink very rapidly for about 1
second. This rapid blinking is when the sensor Auto
Calibrates (measures) the detected train car distance.
That distance is saved in the memory of the sensor.
6. After the rapid flashing the sensor LED will go out for 2
seconds and then return to normal operating mode. The
LED should go back on since it now detects the rail car on
the track in front of it. Move the rail car and the LED
should go out.
NOTE: It is BEST to set the timeout adjustment to zero so
that the LED will go out immediately after you move the
rail car. This makes confirming the correct operations
much easier.

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7. Anytime that you want to use your own setting, simply
adjust the trim pot accordingly using the provided
screwdriver. When the trim pot is zero, the Auto
Calibrate value is used and the trim pot is ignored. When
the trim pot is non-zero, the setting of the trim pot is
used.
NOTE: Auto Calibrate works in either wide zone or narrow
zone modes. In wide zone mode the software adds 1mm to
the detected zone. In narrow zone mode, it subtracts 1mm.
In both cases this happens to assure that the detector sees the
rail car using the Auto Calibrated settings.
INSTALLATION and TESTING
The default setting 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.

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Connect the RED power wires to your 12VDC 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.
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.

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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, press the SELECT button twice.
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

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where you want it. Once set you will not have to adjust it
again. Ever.
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 which
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

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(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.
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

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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.
TRIGGER TIMEOUT SETTINGS
Rotate the trim pot 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 pressing the
SELECT button 4 times. This is a toggle type switch. To turn
OFF the extra time, press the SELECT button 4 times again.

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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.
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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