Zmodell Sound Module for Märklin 87210 Entertainment Car
Oct 23, 2021 15:31:18 GMT -5
Kez, tjdreams, and 7 more like this
Post by scanrail on Oct 23, 2021 15:31:18 GMT -5
Greetings to all,
I would like to introduce my long-time development – sound module for Märklin 87210 Entertainment Car (or "Gesellschaftswagen"). I started it almost right after development of digital interior lighting board for this wagon: azlforum.com/thread/1961/zmodell-digital-decoder-rklin-entertainment, but it took certain time to complete all required research and development routines.
I was inspired by previous variant of digital sound player I introduced some time ago:
azlforum.com/thread/1731/zmodell-digital-sound-player
My idea was to implement almost all features of entertainment cars Märklin produced in H0 (Art. No. 43868 and 43948). These cars are equipped with MicroSD slot and can play user-downloaded music via digital functions. Unfortunately, MicroSD card is too big to fit in Z scale, so I had to use a different solution to equip Z scale entertainment car with the same feature.
After some research, I found a very good single-chip MP3 decoder solution with a minimal quantity of required external components that can play MP3 audio files stored in the flash memory. Many chips often offered in multiple packaging variants, so I had to choose the smallest ones, as the space inside Z scale car is very limited.
For storing MP3 files, I chose the same flash memory chip that used in many sound decoders from many manufacturers, including Doehler & Haass, ESU and others. Memory volume is limited to 16MB – of course, it is much lower than any MicroSD card; nevertheless, it allows to store up to 16-17 minutes of MP3 audio with 128 kbps bitrate that delivers quality very close to audio CD. Maximal length of audio can be extended further (up to 30 minutes) after reducing bitrate to 64 kbps. Once again, most sound decoders use flash memory chips with the same volume.
Sound module is equipped with USB port and detected by OS as a conventional flash disk. No drivers needed. By the way, this is one more reason why I did not use a sound decoder – MP3 files can be copied directly to the device without any additional hardware and software. Copying 16MB of audio files takes about 5 minutes. Nearly the same time required to write a sound project to the most sound decoders.
USB port is separated from the digital decoder with diodes – no need to disconnect a sound module from decoder to copy music to the flash memory.
Sound module is connected to amplified AUX output of FH05B function decoder on which my digital board for Gesellschaftswagen is based. Device control is very simple: by pressing a function button on the command station, it starts repetitive playback of all audio files one by one stored in the flash memory. Music stops when function button is pressed again.
Sound module is equipped with onboard 13x8 mm 0.8W loudspeaker. I developed a special soundbox for it and 3D printed it using clear resin. In order to improve clarity of material, soundbox was covered with a glossy varnish.
Here is the circuit board:
Bottom side:
I switched to a different PCB manufacturer that delivers better quality of the circuit boards. I used a beautiful black mask instead of standard green color – it was impossible with previous manufacturer:
Here is the circuit board fitted with a clear soundbox and brass nickel-plated support pins (made on CNC lathe specially for this project) through which the board receives power from the digital decoder:
After soldering two circuit boards, I got this “sandwich”:
Upgraded digital board is ready for installation into the Gesellschaftswagen:
First test results showed that even in almost ideal conditions (clean wheels and track), onboard 2200 µF buffer is insufficient for stable and satisfying functioning of the sound module – sound restarted too frequently. Surely, it is a well-known fact that sound decoders require a very good and stable electrical contact with track. However, delivering a good electrical contact for passenger car is even a bigger challenge than doing this for locomotive. Here is why:
– In most cases, all locomotive wheels are powered (or almost all). Most 4 and 6-axle locomotives have 8 powered wheels (4 per truck). Standard 4-axle Märklin passenger cars have only 4 powered wheels (not wheelsets), as the electricity is taken only from axles, not wheels themselves;
– Locomotives are heavier than wagons – it also improves quality of electric contact.
Additionally, sound module consumes relatively high current (especially in comparison with LED interior lighting) – around 50-100 mA (while 8-10 warm white LEDs draw only 8-10 mA in total). That’s why 1000-2000 µF capacitor buffer is enough for interior lighting, but less effective for higher current consumers like this sound module.
To solve this issue, I added a dedicated power buffer to the sound module with a total capacity of 6000 µF combined of 60x 100 µF/16V X7R ceramic capacitors (actual capacity may be a bit less due to manufacturer’s tolerance). For this, I used circuit boards I developed some time ago: azlforum.com/thread/1510/buffer-circuit-boards-digital-analog
Now this monstrous device was installed into the Gesellschaftswagen:
Despite it packed with many electronic components, almost nothing is visible through the windows:
Of course, something is visible from a higher angle, but that is the price of adding a sound feature to the car:
What is most important – additional 6000 µF buffer allows to forget about bad contact issues completely – music plays very smoothly and never interrupts. After all these improvements, entertainment car became really heavy – how it weights as much as 24,5 grams – almost like some locomotives.
One more advantage of this sound module: unlike digital sound decoders, it can work as a standalone device; no digital control needed. Device is equipped with onboard 5V voltage stabilizer and can be powered with 5-12 Volts. In can be installed everywhere – for example, in buildings and other places on the layout – where available space is limited. After powering on, device starts repetitive playback of all tracks in the flash memory, and stops once the power switched off.
Small onboard loudspeaker allows saving space when it is critical. However, the circuit board is fitted with separate pads for external speaker (up to 2W).
So, one more digital project in Z scale is now complete.
Best regards,
Alex
I would like to introduce my long-time development – sound module for Märklin 87210 Entertainment Car (or "Gesellschaftswagen"). I started it almost right after development of digital interior lighting board for this wagon: azlforum.com/thread/1961/zmodell-digital-decoder-rklin-entertainment, but it took certain time to complete all required research and development routines.
I was inspired by previous variant of digital sound player I introduced some time ago:
azlforum.com/thread/1731/zmodell-digital-sound-player
My idea was to implement almost all features of entertainment cars Märklin produced in H0 (Art. No. 43868 and 43948). These cars are equipped with MicroSD slot and can play user-downloaded music via digital functions. Unfortunately, MicroSD card is too big to fit in Z scale, so I had to use a different solution to equip Z scale entertainment car with the same feature.
After some research, I found a very good single-chip MP3 decoder solution with a minimal quantity of required external components that can play MP3 audio files stored in the flash memory. Many chips often offered in multiple packaging variants, so I had to choose the smallest ones, as the space inside Z scale car is very limited.
For storing MP3 files, I chose the same flash memory chip that used in many sound decoders from many manufacturers, including Doehler & Haass, ESU and others. Memory volume is limited to 16MB – of course, it is much lower than any MicroSD card; nevertheless, it allows to store up to 16-17 minutes of MP3 audio with 128 kbps bitrate that delivers quality very close to audio CD. Maximal length of audio can be extended further (up to 30 minutes) after reducing bitrate to 64 kbps. Once again, most sound decoders use flash memory chips with the same volume.
Sound module is equipped with USB port and detected by OS as a conventional flash disk. No drivers needed. By the way, this is one more reason why I did not use a sound decoder – MP3 files can be copied directly to the device without any additional hardware and software. Copying 16MB of audio files takes about 5 minutes. Nearly the same time required to write a sound project to the most sound decoders.
USB port is separated from the digital decoder with diodes – no need to disconnect a sound module from decoder to copy music to the flash memory.
Sound module is connected to amplified AUX output of FH05B function decoder on which my digital board for Gesellschaftswagen is based. Device control is very simple: by pressing a function button on the command station, it starts repetitive playback of all audio files one by one stored in the flash memory. Music stops when function button is pressed again.
Sound module is equipped with onboard 13x8 mm 0.8W loudspeaker. I developed a special soundbox for it and 3D printed it using clear resin. In order to improve clarity of material, soundbox was covered with a glossy varnish.
Here is the circuit board:
Bottom side:
I switched to a different PCB manufacturer that delivers better quality of the circuit boards. I used a beautiful black mask instead of standard green color – it was impossible with previous manufacturer:
Here is the circuit board fitted with a clear soundbox and brass nickel-plated support pins (made on CNC lathe specially for this project) through which the board receives power from the digital decoder:
After soldering two circuit boards, I got this “sandwich”:
Upgraded digital board is ready for installation into the Gesellschaftswagen:
First test results showed that even in almost ideal conditions (clean wheels and track), onboard 2200 µF buffer is insufficient for stable and satisfying functioning of the sound module – sound restarted too frequently. Surely, it is a well-known fact that sound decoders require a very good and stable electrical contact with track. However, delivering a good electrical contact for passenger car is even a bigger challenge than doing this for locomotive. Here is why:
– In most cases, all locomotive wheels are powered (or almost all). Most 4 and 6-axle locomotives have 8 powered wheels (4 per truck). Standard 4-axle Märklin passenger cars have only 4 powered wheels (not wheelsets), as the electricity is taken only from axles, not wheels themselves;
– Locomotives are heavier than wagons – it also improves quality of electric contact.
Additionally, sound module consumes relatively high current (especially in comparison with LED interior lighting) – around 50-100 mA (while 8-10 warm white LEDs draw only 8-10 mA in total). That’s why 1000-2000 µF capacitor buffer is enough for interior lighting, but less effective for higher current consumers like this sound module.
To solve this issue, I added a dedicated power buffer to the sound module with a total capacity of 6000 µF combined of 60x 100 µF/16V X7R ceramic capacitors (actual capacity may be a bit less due to manufacturer’s tolerance). For this, I used circuit boards I developed some time ago: azlforum.com/thread/1510/buffer-circuit-boards-digital-analog
Now this monstrous device was installed into the Gesellschaftswagen:
Despite it packed with many electronic components, almost nothing is visible through the windows:
Of course, something is visible from a higher angle, but that is the price of adding a sound feature to the car:
What is most important – additional 6000 µF buffer allows to forget about bad contact issues completely – music plays very smoothly and never interrupts. After all these improvements, entertainment car became really heavy – how it weights as much as 24,5 grams – almost like some locomotives.
One more advantage of this sound module: unlike digital sound decoders, it can work as a standalone device; no digital control needed. Device is equipped with onboard 5V voltage stabilizer and can be powered with 5-12 Volts. In can be installed everywhere – for example, in buildings and other places on the layout – where available space is limited. After powering on, device starts repetitive playback of all tracks in the flash memory, and stops once the power switched off.
Small onboard loudspeaker allows saving space when it is critical. However, the circuit board is fitted with separate pads for external speaker (up to 2W).
So, one more digital project in Z scale is now complete.
Best regards,
Alex
