HEMY's electronics in the future #22
Replies: 8 comments 4 replies
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The new design looks exciting! I am also thinking about designing a new board based on ESP32, with FRAM, RTS, ST4 (no audio connector), home sense, (and maybe limit sensor), push-button switch, and wifi/bluetooth/GPS support via connectors. The push-button switch makes a lot of sense to me because the current rocker switch you used is quite hard to source in North America. ESP32 is a lot cheaper than Teensy. I still prefer the idea of plug-in stepper drivers than integrated drivers, because of the cost: you can get two TCM2209 for $10, and with some soldering it works well. For integrated drivers, the JLCPCB building cost can be much higher with all of the components around them. The 50x50 board is too small for this. Maybe 70x70 is large enough. I will wait for your 2.0 step files to see what's the largest board I can go with. |
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@chunhaow Any progress in your board design? I saw you have modified the board a lot in your recent build. Would you like to share your design some time in the near future? I am not an electronic engineer, but am very much interested in your idea of using ESP32 and TMC2209 solution! I can try to look into it and share my experience over your design (not necessary to be mature) if the schematic and PCB files are available :-) |
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No progress yet. I suddenly got very busy and won't have time working on this until next Spring. I will let you know once I have the schematic ready. My biggest theoretical question now is whether or not an ESP32-S3 will work. There is mixed information in Onstep groups.io. |
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Nowadays, there are so many ESP32-based cards with AI capabiities. It might be possible to use such kind of cards for automatic star recognition, voice command/assistant, and so on... |
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Be aware of the power of the ESP32 compared to the Teensy. For effective interpolation guidance and reasonable goto speed, the Teensy is currently more suitable with OnStepX and HEMY. Several discussions on the OnStep forum highlight differences in performance. An ESP32 is already present on the HEMY PCB (supports the web server) and sends commands to the motherboard via a serial link. I am more in favour of separating functions (such as object-oriented programming vs scripts): the ESP32, which currently supports the web server, could later be used for AI capabilities, for example. |
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wait, this is just a rough draft, with major design flaws... And for the record, the goal is not to make the cheapest board (look at a turnkey 3D printer board for that...), but a tailor-made compact board with best-in-class refinements, (almost) full SMD to avoid hand soldering The ESP32 has much less computing power, the TMC2209 is much less performant compared to the 5160... already said, you're welcome to use and modify the project for your use-case (and fun !), but keep in mind the initial goals that lead to this design :) BTW, the sourcing problem is a real point. did you try newark or element14 ? (other brands of AVnet group) |
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No, but neither is needlessly* spec-ing obscure parts--and there are a few "unicorn" (pun not intended, but recognized) parts in the current build. Three that come to mind are the Teensy, the handle, and the power switch; each of them (AFAICT) has only one source in North America (SparkFun for the Teensy; Newark for the handle and the switch), and has no reasonable substitutes. US$3+ for the switch, plus $10 shipping, is kind of pricey for what it is, particularly when there's not much other reason to be ordering from Newark; another option that's more generic, or more widely available, would be appreciated. If there's a reason it needs to be that switch and only that switch, so be it. But it's a little annoying to spend $10 to ship a $3 switch when you don't have any other reason to order from that vendor. But with that said, all three parts together, including shipping, total about US$50. I'd rather spend less if I can, but if I'm already spending hundreds of dollars building this thing, I don't suppose it makes a great deal of difference. *and I'm not saying here that this is what you're doing, just that to do so also isn't the best way to go |
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legit :) comments are always welcome i spent some time finding a cute (and small) switch that fits the board, this one is all i wanted. If you find a better choice, fell free to share the reference ! Teensy is a major choice of the core project, TeenAstro, because it is the most powerful µC, and the firmware code has been optimized for it (some work had to be done to add a hardware layer abstraction and ESP32 support, but i haven't followed the progress ...) for the handle, it's HEMY's hardware related, and I'm not involved into this part of design. I let Polvinc discuss about it, however it's not a big deal to adjust holes to fit another part |
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Interesting discussion, and above all some very perceptive points of view. From France, we don't have the same perspective on component sourcing in North America or elsewhere in the world. As Lordzurp says, the original design of his electronics, which I helped to complete, is based on choices that don't necessarily take into account the notion of sourcing outside France. The criteria are based on considerations of integration, size and other various specifications. Please let us know what you think! Above all, sensible proposals that meet a real need. The TeenAstro Redux card is intended to be as generic as possible and with the best possible integration choices, which was the designer's wish from the outset (Lordzurp, you can of course contradict me if you wish!). As far as the design of HEMY is concerned, it's 100% my own, and I've necessarily made choices that correspond to what I have in stock (hence the profiles on v1, hence the twin-axis motors, hence the handle, etc). I'm also open to suggestions for improving the design. I'll discuss the rest in the HEMY v2.0 thread. My short-term strategy, to get the best electronics in the end, is to go back to using off-the-shelf modules like bigtreetech's TMC5160 over the next few months. I'm thinking of going back to a simpler design with integrated modules to validate the rest of the electronics. Indeed, the current design is really well done, but there are still a few small points that make me think that the TMC2660s aren't the best choice for the future. I plan to (re)test the TMC5160s with the rest of our design to validate the board, and then integrate all the components from the TMC2160s or 5160s on top. This way, we'll get the best drivers step by step, with the best recommendations in terms of electronics. It's a bit of a step backwards, as I find that their integrated design is a little short on components compared to the manufacturer's recommendations, quite imposing and lacking in electronic safety. As I said earlier, our hobby is to get closer to the ‘ultimate’ control board for an astrophotography mount. My other hobby is to make the mechanics of an open-source mount that aims to be as high quality as possible, at a relatively reasonable price. |
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A couple of other thoughts:
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Thank you for these two points. |
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I hadn't thought to look on Aliexpress for the battery, but you're right, they're there--quoting delivery the end of April. I assume the issue is that they can't ship by air. Bother, but realistically it's unlikely I'd be using my mount before then anyway. |
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I spent a lot of time reviewing HEMY's current electronics, designed in collaboration with another more generic project (TeenAstro Redux). Personally, I use OnStepX and not TeenAstro. During reviews of the first boards, we noted a few minor problems: defects in the footprint of the M.2 connector, and also some parasitic noise on the motor tracking.
As a result, I launched a new electronic board design, with integrated TMC2160s (equivalent to the 5160s, which are more modern but more complex to integrate) instead of the 2660s.
I also made a design with ready-made Polulu TMC5160 modules (more expensive, but guaranteed to work).
I'll update the GitHub when I'm ready!
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