Zmodell digital board w/sound for Märklin entertainment car
Apr 5, 2024 18:07:57 GMT -5
Kez, tjdreams, and 6 more like this
Post by scanrail on Apr 5, 2024 18:07:57 GMT -5
Hi friends,
Mastering new design approaches and appearing of the new, more advanced electronic components brought me an idea to revise one of my earlier developments and to create a new version of it – I am talking about the digital board for the entertainment car (Märklin 87210).
I introduced the first version 3 years ago, in 2020: azlforum.com/thread/1961/zmodell-digital-decoder-rklin-entertainment. After several months, the sound module for this car followed: azlforum.com/thread/2044/zmodell-sound-module-rklin-entertainment.
The biggest challenge with the first version of this board was how to equip it with the sufficient power buffer which would allow smooth and stable functioning of the sound module. Like all digital sound decoders, my sound module is very demanding to the quality of electric contact with the tracks; also, it likes higher track voltage – 14 volts, just like sound decoders, too.
Unlike most locomotives which have as much as 8 connection points with the tracks (each of 8 wheels), most Märklin standard passenger cars have only 4 of them (the power is collected from axles, not from wheels). Together with lower weight, it makes the passenger car much more vulnerable to any imperfections like dust, fiber and grease – very common factors that decrease the stability of electric connection between the wheels and tracks. Märklin 87210 entertainment car is not an exclusion here – it has only 4 electric points (equal to the number of axles), too.
It turned out to be virtually impossible to endlessly pack the board with ceramic capacitors which are also less efficient as energy storage devices in comparison to most other capacitor types. At the same time, the board had to remain easily removable – this is a necessary requirement, because you need to unscrew the board in order to write new music on it. All this forced me to look for a different solution.
Later, such a solution appeared: new types of capacitors entered the market – with higher energy density and smaller in size. After successful usage of them in some of my other developments, for example, in digital decoders for VT 98 railbuses, I decided that it is a perfect chance to prove their efficiency in this challenging project, too.
Someone may ask why not to switch to supercapacitors if such a high capacity is needed. The answer is obvious: it is still impossible with the current technology to pack sufficient energy in a small enough volume. Of course, very small supercapacitors exist indeed, but they have very low nominal voltage and also too high internal resistance – this means that they can’t provide sufficient current in this application and only suitable for buffering LED interior lighting which indeed requires very low voltage and consumes very low current.
So, here is it – the new digital board for Märklin 87210 entertainment car:
Side view:
Bottom side:
I managed to fit nine 470 µF 16V tantalum polymer capacitors on the circuit board which results in a huge 4230 µF energy storage buffer. Along with much higher efficiency of this type of capacitors over ceramic models it brings a huge advantage over previous solutions I used in the first version of the board.
I added red tail lights to both ends of the car using small circuit boards with 0402 LED on each. Of course, it is not necessary in real usage scenarios, but I did it here in order to show the “maximum trim” – what is possible at all. I used a different way of mounting these small circuit boards here – they are attached to the main board with photo-etched nickel silver rails.
The sound module is equipped with micro USB socket for loading music:
I would like to remind that my sound solution offers a very important advantage over most digital sound decoders – possibility of loading music without any external devices (most sound decoders require a programmer for this, and such a device is specific to each manufacturer). The module is detected by the PC as a regular USB drive.
The volume of the flash memory installed in my sound module is 16 MB. The same volume is used in all sound decoders. It allows to store 4-5 songs in MP3 format with 128 kbps bitrate. It is possible to increase the total length of stored audio by reducing the bitrate. It is safe to use 96-112 kbps bitrate – you will hardly notice any difference with 128 kbps. The total length can be doubled – as much as half an hour of music can be stored in the module when 64 kbps bitrate is used, but it is not recommended to go down further, otherwise the audio quality will decrease dramatically.
Someone may ask why I did not use MicroSD cards here in order to increase the space for storing more music. The answer is obvious – unfortunately, even tiny MicroSD cards are too big to fit in Z scale car.
It takes around 5 minutes to completely write the flash drive with music. I obtained a special angled USB cable which is very helpful if the board is fitted with red tail lights:
The small boards with red LEDs must be bent downwards before the installation:
The board completely prepared for the installation looks like this:
The installation is very easy – just unscrew the stock analog board and replace it with the new “portable multimedia center”:
This is how the digital board looks when installed into the entertainment car:
In my case, I completed one more step – I prepared the openings for red tail lights. I carefully drilled them with 1 mm drill bit and then filled the holes with short pieces of red fiber optic:
The installation is very neat – almost nothing is visible through the windows except transparent soundbox on the right and a small part of USB socket on the left:
Here is the list of functions:
F0 – Directionally controlled red tail lights (if installed)
F1 – Disco lights
F2 – Normal interior lighting (doors)
F3 – Normal interior lighting (center)
F8 – Sound (if the sound module is installed)
The disco lights are realized here using special RGB chip LEDs that play a random sequence which is always different for each LED. This provides a very realistic effect of disco lights used in real life. The sound function activates cyclic playback of all MP3 files stored in the memory. Of course, all functions can be remapped – it is a standard for all decoders based on Doehler & Haass technology.
I also added a possibility of adjusting the brightness of normal interior lighting with the help of small trimming resistor – this feature was absent in the first version. I had to use this method because dimmable amplified outputs AUX1 and AUX2 are occupied by more powerful consumers – the sound module and disco lights, and only non-amplified non-dimmable AUX3 and AUX4 outputs are available for normal interior lighting.
Another important improvement over the previous version is native support of analog mode – something that can be crucial for some users (it was impossible to realize it in the first version that used Doehler & Haass FH05B 1st generation function decoder). Furthermore, integrated energy storage module remains functional in analog mode, too – such a possibility is not common to many digital decoders, but I managed to realize it here.
And that’s not the end – you can choose what functions to activate in analog mode by adjusting decoder settings. For example, it is possible to set up the car to operate with disco lighting either with normal lighting, according to your choice. Of course, the sound can play in analog mode, too, and the sound function is set up to do so by default.
As I already mentioned above, the sound module likes higher track voltage – 14 volts in digital mode recommended. Higher voltage increases the efficiency of energy storage module and allows it to discharge longer during power interruption – this makes functioning of the sound feature more stable. Of course, the digital board can work without a sound module, too – latter is an optional part. In this case, the track voltage of 10-12 volts is quite enough.
After installing the digital board with sound module, the car becomes quite heavy and weighs 22.5 grams. But the big weight is not a disadvantage in this case, as it further increases the stability of electric contact with the tracks.
Best regards,
Alex
Mastering new design approaches and appearing of the new, more advanced electronic components brought me an idea to revise one of my earlier developments and to create a new version of it – I am talking about the digital board for the entertainment car (Märklin 87210).
I introduced the first version 3 years ago, in 2020: azlforum.com/thread/1961/zmodell-digital-decoder-rklin-entertainment. After several months, the sound module for this car followed: azlforum.com/thread/2044/zmodell-sound-module-rklin-entertainment.
The biggest challenge with the first version of this board was how to equip it with the sufficient power buffer which would allow smooth and stable functioning of the sound module. Like all digital sound decoders, my sound module is very demanding to the quality of electric contact with the tracks; also, it likes higher track voltage – 14 volts, just like sound decoders, too.
Unlike most locomotives which have as much as 8 connection points with the tracks (each of 8 wheels), most Märklin standard passenger cars have only 4 of them (the power is collected from axles, not from wheels). Together with lower weight, it makes the passenger car much more vulnerable to any imperfections like dust, fiber and grease – very common factors that decrease the stability of electric connection between the wheels and tracks. Märklin 87210 entertainment car is not an exclusion here – it has only 4 electric points (equal to the number of axles), too.
It turned out to be virtually impossible to endlessly pack the board with ceramic capacitors which are also less efficient as energy storage devices in comparison to most other capacitor types. At the same time, the board had to remain easily removable – this is a necessary requirement, because you need to unscrew the board in order to write new music on it. All this forced me to look for a different solution.
Later, such a solution appeared: new types of capacitors entered the market – with higher energy density and smaller in size. After successful usage of them in some of my other developments, for example, in digital decoders for VT 98 railbuses, I decided that it is a perfect chance to prove their efficiency in this challenging project, too.
Someone may ask why not to switch to supercapacitors if such a high capacity is needed. The answer is obvious: it is still impossible with the current technology to pack sufficient energy in a small enough volume. Of course, very small supercapacitors exist indeed, but they have very low nominal voltage and also too high internal resistance – this means that they can’t provide sufficient current in this application and only suitable for buffering LED interior lighting which indeed requires very low voltage and consumes very low current.
So, here is it – the new digital board for Märklin 87210 entertainment car:
Side view:
Bottom side:
I managed to fit nine 470 µF 16V tantalum polymer capacitors on the circuit board which results in a huge 4230 µF energy storage buffer. Along with much higher efficiency of this type of capacitors over ceramic models it brings a huge advantage over previous solutions I used in the first version of the board.
I added red tail lights to both ends of the car using small circuit boards with 0402 LED on each. Of course, it is not necessary in real usage scenarios, but I did it here in order to show the “maximum trim” – what is possible at all. I used a different way of mounting these small circuit boards here – they are attached to the main board with photo-etched nickel silver rails.
The sound module is equipped with micro USB socket for loading music:
I would like to remind that my sound solution offers a very important advantage over most digital sound decoders – possibility of loading music without any external devices (most sound decoders require a programmer for this, and such a device is specific to each manufacturer). The module is detected by the PC as a regular USB drive.
The volume of the flash memory installed in my sound module is 16 MB. The same volume is used in all sound decoders. It allows to store 4-5 songs in MP3 format with 128 kbps bitrate. It is possible to increase the total length of stored audio by reducing the bitrate. It is safe to use 96-112 kbps bitrate – you will hardly notice any difference with 128 kbps. The total length can be doubled – as much as half an hour of music can be stored in the module when 64 kbps bitrate is used, but it is not recommended to go down further, otherwise the audio quality will decrease dramatically.
Someone may ask why I did not use MicroSD cards here in order to increase the space for storing more music. The answer is obvious – unfortunately, even tiny MicroSD cards are too big to fit in Z scale car.
It takes around 5 minutes to completely write the flash drive with music. I obtained a special angled USB cable which is very helpful if the board is fitted with red tail lights:
The small boards with red LEDs must be bent downwards before the installation:
The board completely prepared for the installation looks like this:
The installation is very easy – just unscrew the stock analog board and replace it with the new “portable multimedia center”:
This is how the digital board looks when installed into the entertainment car:
In my case, I completed one more step – I prepared the openings for red tail lights. I carefully drilled them with 1 mm drill bit and then filled the holes with short pieces of red fiber optic:
The installation is very neat – almost nothing is visible through the windows except transparent soundbox on the right and a small part of USB socket on the left:
Here is the list of functions:
F0 – Directionally controlled red tail lights (if installed)
F1 – Disco lights
F2 – Normal interior lighting (doors)
F3 – Normal interior lighting (center)
F8 – Sound (if the sound module is installed)
The disco lights are realized here using special RGB chip LEDs that play a random sequence which is always different for each LED. This provides a very realistic effect of disco lights used in real life. The sound function activates cyclic playback of all MP3 files stored in the memory. Of course, all functions can be remapped – it is a standard for all decoders based on Doehler & Haass technology.
I also added a possibility of adjusting the brightness of normal interior lighting with the help of small trimming resistor – this feature was absent in the first version. I had to use this method because dimmable amplified outputs AUX1 and AUX2 are occupied by more powerful consumers – the sound module and disco lights, and only non-amplified non-dimmable AUX3 and AUX4 outputs are available for normal interior lighting.
Another important improvement over the previous version is native support of analog mode – something that can be crucial for some users (it was impossible to realize it in the first version that used Doehler & Haass FH05B 1st generation function decoder). Furthermore, integrated energy storage module remains functional in analog mode, too – such a possibility is not common to many digital decoders, but I managed to realize it here.
And that’s not the end – you can choose what functions to activate in analog mode by adjusting decoder settings. For example, it is possible to set up the car to operate with disco lighting either with normal lighting, according to your choice. Of course, the sound can play in analog mode, too, and the sound function is set up to do so by default.
As I already mentioned above, the sound module likes higher track voltage – 14 volts in digital mode recommended. Higher voltage increases the efficiency of energy storage module and allows it to discharge longer during power interruption – this makes functioning of the sound feature more stable. Of course, the digital board can work without a sound module, too – latter is an optional part. In this case, the track voltage of 10-12 volts is quite enough.
After installing the digital board with sound module, the car becomes quite heavy and weighs 22.5 grams. But the big weight is not a disadvantage in this case, as it further increases the stability of electric contact with the tracks.
Best regards,
Alex
