CAN-digital-Bahn
The TachoMesser CAN
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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 counting result and the hence calculated velocity in the data format of the speed of the Central Station 2 is then released via the CAN bus from the TachoMesser.
This information can be processed at any location on the bus or sent to a PC via an interface. If the correspondent locomotive is active in the CS2's display, then the result is also indicated there.
A PC-version of the TachoMesser for USB 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, you 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.
There is also a suitable lengthening for the screw. 
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There's also the possibility 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 CAN:
The connection to the CAN bus is quite simple, this can be done with the same cable (MiniDIN6 & miniDIN10) as with the CC-Schnitte at every 10-pin socket in the system. If one works a little bit on the cap of the plug, one can put the TachoMesser even directly to a CS2.
A particular electrical power supply for the module is not required.
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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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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The operation with the CS2 is quite simple.
If one puts the TachoMesser to the system, then the LED located on the circuit board should start blinking for a little while. This is the sign that the TachoMesser works and has voltage.
To every TachoMesser CAN there is a locomotive card on which the data for the TachoMesser is deposited, one puts this in the CS2 and the TachoMesser is already logged on.
The TachoMesser CAN as a Lokomotive in the CS2 has six functions. However, the settings stored in the TachoMesser can not be edited .
The functions have the following meanings:
F1: Selection of the encoder's resolution.
F1 on, 4 pulses per rotation. F1 off, 200 pulses per rotation.
F2 - F6 stand for different scales in the TachoMesser's display.
F2: scale of the tachometer display = 35 km/h.
F3: scale of the tachometer display = 110 km/h.
F4: scale of the tachometer display = 175 km/h.
F5: scale of the tachometer display = 250 km/h.
F6: scale of the tachometer display = 350 km/h.
In the default setting F5 is active, which stands for a TachoMesser's resolution of 250 km / h.
Unfortunately I have not found a way to adapt the scaling of the tachometer in the CS2 by pressing the function keys, though it is possible to write the data, but I have not found a way how I can get the display automatically reloaded. So I’m afraid that one still needs doing this by hand.
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Driving the lokomotive which is to be measured can be carried out via the second controller of the CS2.
If a control program is coupled to the CS2, one can take the locomotive "TachoMesser" and then also read the speed. It needs to be observed here only that all settings that affect the speed, were set to zero and that the display is conform to the scaling of the selected function in the TachoMesser. (F2-F6).
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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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