Domburg KeerPlus3 User manual

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Domburg Train Support
Your partner in model railway technology
DTS Manual: KeerPlus3
Reverse loop solution for DCC model
railways
Version 2 - 2019

KeerPlus3 manual │ version 3 - 2022
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Content
Introduction ..........................................................................................................................................................3
The workings of the KeerPlus3 ..............................................................................................................................4
The functionality of the KeerPlus3....................................................................................................................4
Turning loop requirements ............................................................................................................................... 5
Assembly...............................................................................................................................................................5
Overview KeerPlus3..............................................................................................................................................6
Connecting the KeerPlus3.....................................................................................................................................7
Supply voltage ...................................................................................................................................................7
DCC Signal ......................................................................................................................................................... 7
The Loop............................................................................................................................................................8
Switching outputs..............................................................................................................................................9
Occupancy report............................................................................................................................................10
Frequently asked questions................................................................................................................................11
I connected everything, when the train enters the reversing loop I get instant closure ...............................11
The train gives a short circuit when it enters section 3 from section 2. (Or from S2 to S1)...........................11
I get no busy signal on the busy signal module...............................................................................................11
It gives a busy signal on S1 while the locomotive is running in S3.................................................................. 11
Very occasionally I get a closure when it enters one of the sections .............................................................11
Afterword............................................................................................................................................................11

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Introduction
Thank you for purchasing the KeerPlus3. This article is specially designed for users looking for a reversing
loop solution that is efficient and simple to apply in addition to being cost-effective.
On a digital model railway, a short circuit caused by applying a reversing loop or by creating a differently
polarised part of the track is a common problem. These problems are easily solved by applying a
reversing loop solution which allows part of the track to change polarity. There are two types of circuit in
this, the short circuit method and the current detection solution. The KeerPlus3 only uses the current
detection method. In this manual, we explain how the solution works and how it can be applied to your
model railway.
I wish you much ease of use with the KeerPlus3, should you have any suggestions for improvement of the
product or a critical note. Please let me know by sending an email to [e-mail]
Sincerely,
Martin Domburg
Domburg Train Support
Additional accessories that can be ordered separately:
-Printed circuit board mounting kit
-Mounting frame
-Power supply Meanwell GS36E12
Disclaimer:
The KeerPlus3 was commissioned by Domburg Train Support and developed by Vincent Bogers.

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The operation of the KeerPlus3
The functionality of the KeerPlus3
The KeerPlus3 works entirely on the basis of current detection divided into three sections. Current
detection means that each section is detected over its entire length for power consumers such as
locomotives or carriages with lights. In short, anything that consumes power.
As mentioned, the module uses three sections. As soon as the first section (S1) is activated by detection,
the module switches the second section (S2) and the last section (S3) to the same polarity as S1. Section
S2 is then driven and as soon as the locomotive activates the last section S3, the module immediately
switches S2 and the last section S3 to the opposite polarity. The first section S1 remains unaffected so it
can be ridden again.
This works identically when the reversing loop is driven from the other direction. In rest mode, the
module "sniffs" for a consumer on sections S1 and S3. As soon as S1 is activated, the module puts S2 and
S3 in the same polarity and switches at S3 together with S2. If S3 is switched first, the module puts S1 and
S2 in the same polarity and as soon as S1 is activated it switches S1 and S2 to the other polarity. Since S3
then remains in place, a train can simply re-enter there.
.

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Requirements of the Turner loop
Because the module does not switch the first section, the rule applies that section S2 must be at least
the length of the longest detected train. Should the train not fit in it (e.g. a railcar or a train with a
driver's cab), a short circuit would occur as soon as the wagons still in the first section enter the reverse-
polarised S2.
Summary: S2 should be the length of the longest detected train.
Besides the middle section S2, we also talk about S1 and S3, the two outer sections. The
recommendation is to use about 1.5x a locomotive length. In theory, a length of 5 centimetres would be
enough to generate good detection. However, practice shows that contact between the rails and the
wheels is still sometimes not guaranteed. To make the reversing loop sections work reliably and stably,
we therefore recommend using a longer length for this.
Assembly
The KeerPlus3 has 4 mounting points. It is recommended to mount the board at height because of the
heat generation of the voltage regulator. Preferably with the components at the top.
Mounting the module in upside-down or sideways position is also possible as long as you take into
account the cooling of the cooling element.
For mounting, you can use the circuit board mounting set which you can find
in the web shop.

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Connecting the KeerPlus3
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Overview KeerPlus3
1Power supply voltage (note: always connect)
2DCC Signal from the central unit (note: always connect)
3/4 Section 3 (S3) A/B
5/6 Section 2 (S2) A/B
7/8 Section 1 (S1) A/B
9 Switching output Common
10/11/12 Switching outputs S1/S2/S3
13 Switch position S1
14 Switch position S2
15 Switch position S3

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Connecting the KeerPlus3
Supply voltage
The supply voltage to be offered to the KeerPlus3 can be provided in three different ways:
1. DC voltage 12-16 VDC
2. AC voltage 12-16 VAC
3. DCC Signal
The DCC signal refers to the Track Output of the central unit. Power supply by a DC voltage supply is
preferred, but as not everyone has one, it is also possible to use an AC transformer or the DCC voltage.
The module is not polarity sensitive so it does not matter where you connect the plus and minus.
DCC Signal
The illustration shows the DCC input (2) to which you should connect the raw DCC voltage from your
central unit. Basically, the left terminal is B and the right terminal is A. In the wiring diagram, we have
given the A a blue colour and the B a black colour.
Unfortunately, the output is not the same for every central unit so you need to find out by trial and error
which sequence should be applied for you. Another variable is the way you have arranged the polarity on
your layout.
If, after connecting the reversing loop, you get a short circuit on your central unit as soon as a locomotive
enters the reversing loop, it is an indication that you should swap the A and B connection on terminal 2 of
your module.

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The Turner loop
In the image above, you can see the three sections drawn with their corresponding connection to the
module. In this example, you can see that the outer rail is A (blue) and the inner rail is B (black). This may
also be the other way around, as long as all three sections are A on the same side and B on the same side.
On the terminals, you should also maintain the A and B connection consistently. If you swap the A and B
on the terminals of 1 section, you will get a closure in that section.
What is also important is that you do not mix up the order of the sections, otherwise the module will
switch incorrectly.
Finally, it is important that all sections are interrupted on both sides in both rails. You can do this by
using rail splices or cutting the rails. The sections should therefore not make contact with each other in
both A and B. There are three LEDs on the module which indicate the polarisation status of each section.
If the LED is off, the polarisation relay of that section is off and if the LED is on, the polarisation relay of
that section is on and the section is re-polarised.
You should always connect the DCC signal as well as the
power supply! So perform both connections, otherwise the
KeerPlus3 will not work.
You can also loop the DCC signal to the power input. The
KeerPlus3 does not draw power from the DCC input because
one has other ways to power the module.

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Switching outputs
At the top are 4 screw terminals (9 to 12) which switch based on current detection. As soon as current
detection is present in a section, a second relay will switch between these terminals. There are three
relays in total, one for each section.
Because the contacts are potential-free, you can use them to switch all kinds of things. Think of
turnouts, LEDs, signals, relays and so on. Operation is quite simple. You connect any voltage or signal,
whatever suits you best, to terminal 9. As soon as section 1 is detected, this voltage will be transferred
to terminal 10, in case of detection in S2 the voltage will be transferred to terminal 11 and in case of
detection in S3, terminal 13 will receive the voltage from terminal 9.
Note that the relays respond to detection, if you suffer from dirt or poor contact you will hear the relay
switching more often than you would expect. The explanation for this is very simple:
Detection present, relay on. Detection absent, relay off.

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Occupancy notification
The switching outputs can also be used for a busy signal module for control via software.
As you can see from the bottom of the module in the picture, the black wire (DCC-B) goes to the
DR4088LN busy signal module. By the way, this can be any other occupancy module on the market. This is
separate from the DCC connection as written in section 3.2. It is required for the operation of the module
itself.
However, what is important is that the other wire (DCC-A on the diagram) is brought to terminal 9 on the
KeerPlus3. The reason it has to be the other polarity as the one you offer on the busy signal module is
because in this case the busy signal module does not feed the section as normal, but only detects it.
You connect this dcc polarity to terminal 9 with a carbon resistor with the value 10 kOhm (10,000 Ohms).
Only this value will generate a detection on your busy signal module. The resistor can be optionally
ordered with the KeerPlus3 in our webshop. You then wire terminals 10/11/12 (S1/S2/S3 respectively) to
one of the outputs on the busy signal module. Incidentally, it is not compulsory to use all 3 detectors, this
does not affect the operation of the KeerPlus3 in any way. The outputs are electrically separated from the
electronics on the module.