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Post by scanrail on Nov 8, 2021 10:14:41 GMT -5
Digital decoder for SW1500 is already in development now. I have to admit that this task is not easy. Everything told me that I had to use 4-layer circuit board, but I managed to trace everything in only two layers, using 0.15 mm trace width. It was crucial, as the maximal thickness of PCB that allows the housing to sit on the chassis completely is only 0.3 mm (0.012 in) - anything thicker will be too much. It is impossible to produce so thin 4-layer circuit board. Or it will cost more than gold.
Actually, we have only around 1.1 mm available height between the chassis and housing. I tried to find smallest possible components to build a decoder. While many of them are only 0.5 mm thick, some critical components offered in packages with 0.9 mm height. After all, I hope it will work. Test PCB samples were already ordered.
Another potential problem - is a world shortage of chips. Surprisingly, this fact influences on us as well. I managed to find some leftovers of PIC microcontrollers only in China, as no one of big suppliers has them currently in stock (Digikey, Mouser etc). First deliveries are scheduled only to 2022. I hope to get them sooner, once it comes to production run.
Surely, it is not even a question to accommodate any existing decoder in such tight space inside the loco.
That's all I can tell at the moment; I will let everyone know regarding further updates on development.
Greetings, Alex
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Post by BAZman on Nov 9, 2021 0:51:27 GMT -5
Which PIC? I may have access to a few (to start). I've put parts in 'square' board holes (gull-wing easier)
Just thinking. At least you didn't have to go to flex 'boards'
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Post by Deleted on Nov 9, 2021 3:31:05 GMT -5
Alex, try uk.farnell.com, but I don't know if Your parts are available on stock and if they deliver to Ukraine ... Good luck !
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Post by scanrail on Nov 9, 2021 6:19:07 GMT -5
Which PIC? I may have access to a few (to start). I've put parts in 'square' board holes (gull-wing easier) Just thinking. At least you didn't have to go to flex 'boards' PIC16F1825-I/ML in QFN16 4x4x0.9 mm package. Only this one will fit. All other packages are too big - even SOIC/TSSOP with gull-wing outputs. There is not enough space for anything else on the PCB except the smallest QFN packaging at all. Square board holes will not help - SOP packaging is already too thick itself; adding such a big hole in the center of such a thin board will enormously complicate already very complex circuitry, and the board will be so brittle that it will break with a 'blow of wind'. I ordered 20x of these chips from China for test and development purposes - I hope to get them soon. It will be enough to start. However, I would be happy to obtain the next batch from more reliable source. I sold 200x decoders for RS locomotives to US and European customers in total; I expect at least the same demand for SW decoders. Thus, I need 200x PIC16F1825-I/ML. I will be more than happy if you really can help with this somehow. Possibly, they can be found at smaller suppliers locally in the USA. But I will need them only when everything will be ready for production run. Alex, try uk.farnell.com, but I don't know if Your parts are available on stock and if they deliver to Ukraine ... Good luck ! Thank you very much! I already looked everywhere; Farnell is not an exclusion: uk.farnell.com/microchip/pic16f1825-i-ml/mcu-8bit-pic16-32mhz-qfn-16/dp/1841446"Back order today stock arriving week commencing 09/12/22" - that's all they can offer now. Additionally, Mouser offers them for better price - 1,23 € instead of £1.48 for 100+ quantities. Only delivery date is the end of 2022 - and it is the same at all suppliers Best regards, Alex
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Post by markm on Nov 9, 2021 14:22:30 GMT -5
Alex,
I checked with contacts at Microchip/Atmel and the lead time for this chip is absolutely 12 months. You may be able to get a couple through the Microchip samples program with a couple of month lead time. Request will have to be made from. .com or .edu email. Virtually everything in house that is shippable has.
Be cautious with the China chips, they have found reject devices being shipped from there.
Mark
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Post by baumback on Nov 9, 2021 21:37:58 GMT -5
... Be cautious with the China chips, they have found reject devices being shipped from there. Mark I use to work for an aerospace/defense company and counterfeit parts were always a bit problem for the industry, even before covid. We could only purchase directly from the manufacturer or authorized distributor with a certificate of origin. Wise to stay away from parts of questionable origin. Mark
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Post by scanrail on Nov 10, 2021 3:43:55 GMT -5
Hi friends,
Thank you for your concerns - be sure I am even more concerned regarding unknown suppliers than you. Small quantity of chips I ordered from China is only for test purposes - I hope it will work. Surely, it is a subject of extreme importance to get electronic components from reliable sources. But now - with a lead time of 12 months for this single chip everywhere, I simply had no choice. By the way, I already obtained all other required components from Mouser (as well as directly from my suppliers in Germany).
I would just like to save some time and to prepare everything for production run - before Microchip replenish their stock at major suppliers. For this, I need to assemble and test few decoders and to be sure that everything works as expected.
Alex
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Post by BAZman on Nov 10, 2021 13:42:49 GMT -5
So, are you going to mount the components up front where there is space under the board and above the frame?
I assume that you are using an Open Source DCC coding? Besides, it’s just plain code anyway, changing Speed, Direction, Acceleration/Deceleration and Light.
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Post by scanrail on Nov 11, 2021 5:16:38 GMT -5
So, are you going to mount the components up front where there is space under the board and above the frame? Not enough space in this small recess to allocate all required components there. They will be distributed uniformly on the top side of the circuit board. That's why the board should be very thin (0.3 mm/0.012 in). I assume that you are using an Open Source DCC coding? Besides, it’s just plain code anyway, changing Speed, Direction, Acceleration/Deceleration and Light. No, much better Doehler & Haass licensed me their decoder technology. Actually, it will be a decoder with a full set of features offered by D&H, including even firmware updates. I will use their own proprietary chip accompanied by a PIC microcontroller. The set of features will be equal to D&H's popular decoder DH05C. But: please, right now, I don't want to predict or promise anything in advance. Technical preconditions are indeed very tough. This development is a big challenge. At this stage, nothing is guaranteed. I hope very much this development will be successful, and I will do my best it to be like this. Best regards, Alex
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Post by zman on Nov 11, 2021 6:14:13 GMT -5
Best of luck in your endeavors Alex! It is great you are trying to improve and create new technology for Z scale. Thanks for your devotion!
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Post by dazed on Nov 11, 2021 8:39:32 GMT -5
Best of luck in your endeavors Alex! It is great you are trying to improve and create new technology for Z scale. Thanks for your devotion! Agreed, good luck and thank you for stepping up to this challenge.
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