Zmodell Digital Decoder for AZL SD40-2 diesel locomotives

Exciting news. I look forward to having these available.

Offering up prayers for Ukraine, I wish more was being done to help.

you make my day Alex, this is a great news

Hello Eino,

As I have already mentioned above, I will prepare detailed information about all features of the new digital decoder and its characteristics very soon - once I will get a working sample in my hands. I just don't want to repeat a popular mistake of electric car makers who, for example, announce that "our car will do 500 km on a single charge", while actual usage later shows that there are only 300 km under ideal conditions...

Best regards,
Alex

Hi friends,

I am glad to announce that one more development has just been successfully completed – digital decoder for the newest addition from AZL – SD40-2 diesel locomotive, the finest detailed and the best running model from the company. The construction of the chassis allowed to integrate highly efficient energy storage module featuring 2x 470 µF Tantalum Polymer capacitors with thermal and overvoltage protection.

The digital decoder is compatible with all variants of SD40-2 family, including versions with all kinds of noses and also with SD40T-2 locomotives. It is also expected to be compatible with upcoming SD50 and SD60 series (compatibility is yet to be confirmed later).

SD40-2 decoder has a number of special features, such as advanced front lighting and integrated highly efficient energy storage module. The installation of this decoder is very easy – no soldering needed and only one tool is used – Philips PH0 or PH00 cross screwdriver.

So, here is it – the new decoder, top side:



The bottom side. Two buffer capacitors are visible here:



The digital decoders supports the following operating modes: DCC, Märklin/Motorola (MM), SelecTRIX 1, SelecTRIX 2 and also DC Analog mode. Maximum track voltage is 14 V in digital mode and 12 V in analog mode.

Functions

F0 – Directionally controlled headlights
F1 – Dimming function (brightness of headlights reduced by 50%)
F2 – Shunting mode (maximal speed reduced by 50%, short acceleration and deceleration time)

All functions can be remapped according to personal preferences.

Advanced front lighting

SD40-2 family of diesel locomotives counts a big number of variations; each of them also features different configuration of front and rear lights: we have ditch lights, headlights on the nose (noses exist in multiple variants, too), and headlights on the top of the cab – all this brings a lot of possible combinations. My idea was to develop a solution that would be compatible with all variants, and I completed it successfully.

Front end of decoder’s circuit board features two LEDs populated on both sides of the board; each LED is a different type. LED on the top is a small side-emitting one; it is intended for all versions of SD40-2 with top headlights – with low nose, but with headlights on the top of the driver’s cab, and also ones with high nose.





LED of the bottom side of the board is SMD 3528 type. It is a default LED for front lights; it lights up headlights on all variants of low noses, and also ditch lights. Weak lights is a common problem for many AZL locomotives. The reason is also known: the lightguides are often very long and curved, and their rear ends are often not properly aligned with the light source. That’s why we have many models with almost invisible headlights.



Ditch lights became the biggest challenge in SD40-2 locomotive, since they are located at the very edge of the front end, and their lightguides are extremely long and have many angles which decrease the brightness of the light dramatically. I decided to fix this issue and after numerous experiments and testing a big number of different warm white LEDs I found a perfect solution.

3528 type LED became the only light source capable of illuminating the ditch lights and headlights in the nose as brightly as if it were located directly behind them. I was so impressed when I saw the ditch lights on my CSX SD40-2 lit so brightly!

The only downside of such a solution is that this LED can be soldered in vertical position only manually. It increases complexity of assembly and overall effort, but I have no doubt that it’s worth it! Here are some pictures:







By default, only the lower LED is activated by F0. To add the upper LED to F0 function, CV33 should be set to 5. Default value is 1. It is also possible to assign both LEDs to different functions and switch them separately during operation. The brightness of all three LEDs can be adjusted separately. Brightness in dimming mode is adjustable, too.

Integrated energy storage module

During assessing the space inside the locomotive available for the digital decoder, it became clear to me that I can easily integrate such a useful thing as energy storage module here. Although most mass-produced decoders do not offer this feature, many of us know very well how annoying can be jerks, stalls and unstable running of the locomotive over the dirty tracks and potentially problem sections like turnouts, crossings etc. It happens even more frequently when the locomotive runs at low speeds.

I managed to allocate 2x 470 µF Tantalum Polymer electrolytic capacitors on the bottom side of the circuit board. This type of capacitors shows significant gain in energy efficiency in comparison to ceramic capacitors (MLCC) due to much better discharge curve. The circuit also has overvoltage and thermal protection. Also, no need to isolate the metal chassis because these capacitors have plastic housing, and it is safe even if they touch the chassis.

Integrated energy storage module proved its extreme efficiency during testing on a big modular layout with many potentially problem sections of the track like I listed above. SD40-2 locomotive passed all of them without any problems, while other locomotives without storage capacitors stopped there all the time. It is also worth noting that this energy storage module works in analog mode, too.

Installation

The installation of SD40-2 decoder is very easy, no soldering needed – it is a true drop-in solution. Carefully separate the housing and the chassis of the locomotive, remove four screws holding the stock circuit board and dismantle the board:



After this, simply install the digital decoder onto the chassis and fix it with the screws. It is only important to take care of the motor outputs: make sure they sit in the oval holes of the digital decoder correctly and don’t touch the chassis. Actually, the installation is very similar to what we had with SW1500 digital decoder I presented a couple of years ago.

This is how the digital decoder looks installed onto SD40-2 chassis:









SD40T-2 chassis is longer at the rear end, but installation is exactly the same.

Here is a set of pictures showing Southern Pacific SD40T-2 locomotives equipped with my new decoder running on the layout:















I already started production run. Manufacturing such an advanced board of course requires time and effort. I expect the new decoder to be available at the dealers in the USA in around 1.5-2 months.

User’s Manual for SD40-2 digital decoder can be downloaded here:
ZDL-AZL-SD40-2.pdf (351.95 KB)

SD40-2 digital decoder successfully passed all tests on the following equipment:

• Märklin Central Station 3+

• Digitrax DCS240

• Uhlenbrock Intellibox 2

• Doehler & Haass Programmer

• ESU LokProgrammer

All pictures of SD40-2 locomotives have been taken on the wonderful layout of OWL Division of US Z Lines Europe in Löhne, Germany.

Best regards,
Alex

Every DCC Z scale loco I own switches to DC Analog mode automatically. I did not know it could be otherwise. Thank You.

Fantastic new product for us Alex! I will have to get my order in. Looks like this will be a great shunter as well. Amazing work.

Oops! you have dated me! the decoders i have encountered Digitrax DZ123M0 were made for MTL locomotives made almost 20 years ago, and no, they do NOT automatically switch to DC mode, (though i wish when i find an installer has SOLDERED the board to the chassis!!!!-this on a board that is firmly attached to the chassis with springs, not a 'springy' fit pcb which dislodges in cold weather/transit.)  kudos to AZL for the change to screw-mounting PCBs, and DCC boards getting smarter!

Hello Ed,

Although using DC analog PWM is theoretically possible with some decoders, I would advise strongly against using such a controller with this digital decoder. I won't cover any damage to the locomotive and/or digital decoder in case of running it with PWM controller by the warranty.

In general, PWM controllers is a good solution for those who don't want to use DCC but still would like to bring some "digital" features to their analog layouts like smoother motor control, especially at low speeds.

Regards,
Alex