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Thread: Hexapod for a beginner

  1. Hexapod for a beginner

    I've done some reading on this forum before joining and I'm still not sure what the best choice would be so I'm making my own thread.

    I'm a automation engineer with experience in PLC programming with both text based code and ladders. I wan't to evolve my programming skills and I really like the look of the hexapods like PhantomX so I thought why not combine those two. I got very little C++ experience but I would prefer a system involving C++.

    My issue is how to approach this. I like the building process and making stuff from scratch but there is really a ton to learn about these bots and from what I can tell a lot of pitfalls. Would I be better off getting a PhantomX or similar to learn and understand how they work and to learn about the limitations or would it be better to buy separate components and make most of the bot myself? Is it mission impossible to try to do all the hardware work for my first bot on top of learning everything as I go along?

    Should I go "all in" with proper servos for a first build or is it better to just go with a budget rc-hobby servos and train/evolve on a cheap rig? Another aproach could be deciding on servos like the Dynamixel XL430-W250-T that I can use on a PhantomX and then get 3 of them and a Teensy 3.6 (or whatever is good now since the 3.6 is kinda old), 3d print or machine parts for a robot arm and start my training there before going onto the PhantomX.
    Last edited by minim; 07-22-2019 at 06:16 PM.

  2. #2

    Re: Hexapod for a beginner

    Budget RC hobby servos will be a throw-away cost if you actually end up wanting to build a real thing.
    My recommendation would be to go for the AX-12 servos at the very least (i e, a PhantomX)
    The Arduino-style boards are programmed in a form of "C++ lite" so that seems like a good step for your needs.

  3. Re: Hexapod for a beginner

    Then I guess that is a bad idea with hobby servos. I've read docs on the AX-12/RX-18/XL430-W250-T and some forum threads since those are the ones within what I can spend on a first project. But can I ask why you recommend the AX-12 over the XL430-W250-T? From a user without experience only reading about them the XL430 seems like an upgraded version of the AX-12 that you can get for about the same amount of money. The price is similar ($12 difference) but I get a 360 degree contactless encoder, PID control and some other gadgets that the AX-12 lacks. Strenght and speed looks similar.

  4. #4

    Re: Hexapod for a beginner

    The XL430 is fine! It's the new raplcement for AX-12, and as you say, it has some upgrades.
    I don't think Trossen has any hexapod kits for the XL430 yet, but if you're making your own, that's not a problem.

  5. Re: Hexapod for a beginner

    Good good then I'll go with them. It looks like it's easiest to start off with OpenCM9.04 controller too in regards to what people are using so will try that one as a starter until I know what I'm looking for in a robot controller.

    I hope I can find some designs or read me up some on how angles and movements needs to be. Got access to cnc/lathe/3dprinters so making the hardware should be doable as long as I know what to make. Since I have very little knowledge in programming and robotics it will prolly be long lasting project but since the road there is part of the goal that doesn't matter.

    My shoppingcart is this far:
    Robotis - Dynamixel XL430-W250-T
    Robotis - OpenCM 485 Expansion Board
    Robotis - OpenCM9.04-C
    Robotis - OpenCM9.04-Accessory Set
    Robotis - U2D2
    Robotis - Cable-X3P 180mm 10pcs
    Robotis - U2D2 Power Hub Board

    Think I'm missing a hub for the servos but I might have to make me something that fits my design in the end.
    Last edited by minim; 07-24-2019 at 12:22 PM.

  6. #6

    Re: Hexapod for a beginner

    Looks like a good list!

    If you use the "-T" servos, you don't need the 485 expansion board. You can get the "A" variant of the OpenCM and solder in the right headers yourself, I think. At least, that's what I did a while back :-D

    However, I would recommend getting the "-R" servos if possible, because the RS485 protocol is more robust.
    You program it the same way, it's just higher-integrity against interference on the wires. (And you need 4-pin wires)
    ... oh, they don't have a "-R" version of the XL430. Well, then!

    You'll also want a bag of shorter wires (100mm or so) and a bag of the longest wires (I think 240 mm) for when the 180mm wires don't quite work out.

  7. Re: Hexapod for a beginner

    That's what I thought also about the RS485 board but it's mentioned in the documentation. On the XL430-W250-T (-T for ttl) they write the following text "Controller : OpenCM9.04 485 Expansion Board, OpenCR1.0". Might be a copy-paste thing from the rest of the X series with RS485 or it could be that the OpenCM9.04C has the wrong connector so they recommend using the expansion board to get proper connector. Idkn but it got me confused and since shipping was $100 I'd rather get a item to much than missing one ^^ Since you also share my opinion I'll remove it from my list.

    Yeah I think that are for their bigger brothers and they do cost a lot. Since it's a new hobby I'm also not very keen on spending that amount on servos before I know if I can even get them running. I'm still not sure if I should order all 18 before I can see if I get the OpenCM to control a few servos for a robot arm. I bet it's hard to get rid of them if I fail completely Is the noise on TTL a big issue? I don't see many posts about it on the forums.

    I had this idea about just ordering "long enough" to get started and then order the proper pins and connectors at mouser/rscomponents so I can make wires in the proper length for the bot. When building RC models and drones I always make my own cables since I hate having cable mess because a wire is to long. Prolly just a waste of time caring about isn't it hard to get the proper lenght with only 100,180 and 240 to pick from on small bots?

    Thank you for your time helping clueless people like me. It's really appreciated and helps a lot to get help starting out in a proper way.

  8. #8

    Re: Hexapod for a beginner

    The OpenCM 9.04-C needs an adapter cable, or the board, because it doesn't have the right connector.
    The 9.04-A lets you solder in the connectors yourself, so you can buy the right connectors from Digi-Key and they should fit right on.
    Or just get one of the old-style cables and splice one half of each old and new (actually, I think Robotis might be selling one of those already made, too.)
    The carrier board isn't bad, it's just bigger than the 9.04 itself, if you don't really need it. But I've been known to worry too much about the wrong thing in the past, so go with your instinct!

  9. Re: Hexapod for a beginner

    I agreed with you I ordered the -A version and then I put in a order on rscomponents for cables, connectors and pcb header.

    I placed the order today for 6 servos and all the other gear on the shopping list. Since shipping was high from trossen I went with a more local robotis dealer and ofc his warehouse stock was wrong and after the order I got told it was delayed atleast 3 weeks to their store.. Hope I can cancel it and order directly from robotis so I don't have to wait 3 weeks for them to stock it Not that it's a rush but it would be cool to at least start fiddling with the controller and start learning about that.

    The link below has a typo on the Terminal. It should be JST SEH-001T-P0.6 not SHE I think. Atleast that's what hte JST spec says so I went with those.

  10. Re: Hexapod for a beginner

    Maybe it's not allowed to ask about other user groups/discord/irc/forums that is more active than this? I do a lot of reading to get into this hobby but I find it strange that there is no place with massive activity. Robots is the future

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