CAN-digital-Bahn
The TachoMesser is something very different. It is not only a module, the TachoMesser consists of two parts: of an electrical and of a mechanical part. This system is designed for determining the speed of a locomotive.
The first description of this project (in german) can be found in the periodical "Modellbahn Kurier" no.37, that was published in November 2011, indeed, nevertheless, there has been some development since then.
A second article about this topic was published in the periodical "Modellbahn Kurier" no. 40, in November 2012.
Both of the articles (in german) can be found in the press archive
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Basics to come up with the idea:
For the calibration of locomotives with a measuring section a lot of time is always required, especially if the locomotive can also drive very slowly. And right here is where the idea of the TachoMesser begins. It should be able to collect simply and very accurately the speed of a vehicle. This will only function with a cleanly working mechanism and the more accurate the mechanics for such a measurement is made, the better the result.
But that's not the only crucial point for a very good measurement result, because the resolution with which is measured, has a great influence on the result and only with a high resolution of the encoder one is also able to manage such measurements in the shortest time.
The measurement is done by counting the number of pulses in a fixed time. The more pulses per distance is obtained from the encoder, the more accurately one can determine the covered distance and thus the speed. Of course the measurement time must also be accordingly exact.
The CAN-version of the TachoMesser one can find here.
Bima-Modellbau:
The solution of Bima-Modellbau is based on their available H0 roller test benches for the AC variation, which now is available with a special roller block that is equipped with an incremental encoder that provides 200 pulses per rotation. With this mechanism a pulse corresponds to a covered distance of 0.1099 mm.
Because of the high resolution also little speed can be recognized quite well.
Märklin roller test bench H0:
Who already calls his own a roller test bench of Marklin can have it easily upgraded.
The sensor from the battery-powered roller test bench of Märklin 78115 (encoder as a spare part no. 1027729) provides four pulses per rotation. Here, a magnet with a hall sensor is used and each pulse of the encoder corresponds to a path of 4.712 mm. This construction is very robust and when the locomotive is well aligned, one can achieve good results. However, it takes a little time for the recognition of slow velocities.
Who wants a higher resolution for this roller test bench can find assistance from the CAN-digital-Bahn Project.
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The rollerblocks from the CAN-digital-Bahn-Project:
If one wants to reach a high accurateness for the roller test bench of Märklin, then only a new rollerblock can help. Such one now is available from the CAN-digital-Bahn Project for gauge H0 and gauge 1.
All trials, to realise this also for the Minitrix roller test bench in gauge N, have shown that this is possible only with an extremely big temporal and financial effort.
Here you can see a video of the prototype.
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The whole block of the encoder is made from one piece and certainly the most sophisticated solution. Therefor it delivers results that one can call a 'measurement'.
 Gauge H0
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 Gauge 1
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These rollerblocks are furnished with an incremental encoder which delivers 200 impulses per turn. This means that with this mechanism in gauge H0 one gets every 0.09425mm an impulse and in gauge 1 the resolution is 0.157mm.
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The new blocks are simply screwed underneath
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and so the encoder is already mounted to the roller test bench.
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There's also the possibilty to connect almost every own solution to the TachoMesser, because for the analysis with a PC the Tachomesser solely counts the impulses and sends this data once per second without interpretation or to calculate with it. The evaluation program then can be written by everybody individually on the PC, however, one needs no own hardware for the capture any more.
Connection to the PC:
The connection to the PC is effected via a standard USB-cable.
At this point it should be re-emphasized that there is no need for an additional voltage to run the TachoMesser.
It is only neccessary to install the adequate driver.
Connection of the encoder:
The PIN configuration according to the data sheet, if the socket is up.
1 = track B ground
2 = +5Volt
3 = track A
4 = not occupied
5 = ground
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To make things easier, there is a fitting cable for the CdB-encoder available.
blue with yellow plug = ground
black with grey plug = +5Volt
green with green plug = pulse output
Because the cables are very stiff and also short, it is recommended to solder new cables.
A reconstruction of Märklin's encoder, as it is still described in the article of the periodical "Modellbahn Kurier", is not neccessary any more. Instead the encoder can be connected directly to the TachoMesser via screw-type terminals.
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The circuit board of the encoder from Märklin's rollerblock
Märklin's rollerblock with new cables
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In addition to the actual measurement function the tool provides no other functions.
One merely need to select the COM port of the TachoMesser to establish the connection. More settings for receiving the measured values are not needed.
In order that the TachoMesser can be used with as many solutions, it is now possible to set freely the path-length per each pulse. The upper limit is 9.9999 mm / pulse. At values above 10 mm the pulses are already too rare to be able to detect slow velocities. Best results are obtained with values less than 1mm.
The scaling of the tachometer in the service tool automatically adjusts to the received measurement values so that no settings are necessary here.
However, driving the locomotive has to be performed via a separate central unit.
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Calibration with WinDigipet:
As the first model railway software WinDigipet supports the TachoMesser as a tool for calibrating locomotives.
The settings in Win Digipet for the TachoMesser during calibration.
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