Mindstorms H25 robot arm build with 31313 parts (consumer set)

13 thoughts on “Mindstorms H25 robot arm build with 31313 parts (consumer set)”

1. MARIA CLAUDIA 04/11/2017 at 18:31

   hi… MY SON HAS 7 YEARS AND DO IT IN 2 HOURS . THANKS A LOT. WE ARE FROM AMERICA LATINA AND THIS INSTRUCCIONS ARE NEED.

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2. Paul 29/10/2017 at 11:06

   Thanks for your effort converting the H25 for the 31313 set parts – very helpful.

   Here’s a link to a slight modification of your design.

   I’ve added some additional bracing/strengthening to your design to keep the arm more firmly on its drive-shaft and I’ve added in the motor-bracing parts from the original H25 design, as this stiffens up the structure quite nicely.

   I’ve also added a design for an alternative claw, but it’s a bit limited by the restricted part availability of the 31313 set…

   There’s no nice way around the additional Z12 gear, so I’ve not changed that.

   For anybody reading this, I’d like to echo Bjoern’s original warning about instructions generated with LDD – they’re quite difficult to follow, as LDD really likes placing parts in mid-air “for later” and assembling structures from the outside in, meaning you have to strip it all apart again so you can do it from the inside out…but it’s free, and there’s nothing else that does the job, so there’s no point complaining 🙂

   Enjoy moving small things from one place to another 🙂

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   1. Bjoern Post author30/10/2017 at 00:09

      Hi Paul,
      thank you for the feedback and the plan!
      (Hint for people looking for Paul´s plan -> Click on Pauls name to download the LXF-File from google drive)
      Any code for the arm you might want to share as well?
      Björn

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      1. Paul 24/01/2018 at 11:22

         Hello,

         sorry not to reply before now.

         I’ve been playing with this arm with my students and have attached some code which may or may not be of interest.

         Compared to the arm that could be built with the NXT (the previous mindstorms) system, this one is rather limited in terms of its functionality. There are two sensors in the H25 design, one that detects when the shoulder is rotated to a clockwise limit and one which detects the position of the elbow. The elbow sensor is a reflected-light sensor and I’ve found that the L-brick it detects needs a white sticker or similar applied to it to reliably detect it. The elbow sensor could probably detect “how raised” the arm is, but I’ve found it only reliable enough to detect when the arm is fully raised.

         Direct drive of the arm is possible without any code at all – the EV3 block gives you control over the motors as standard. The code I’ve attached here demonstrates sequences of actions which move the arm between a number of pre-defined positions – it’s a sort of a finite-state machine in that respect.

         There are guidance notes in the code itself with regards the functions of the buttons on the EV3 and the correct cabling of the motors. The code has some rudimentary error handling (i.e. it prevents the arm being moved beyond two defined limits and you have to hit the middle button to reset the arm before you can use it at all – this puts the FSM into a known state) and uses a variable to maintain state (i.e. keep track of its current position).

         I’m still using the hit-and-miss claw design in this code – without some sort of sensor to detect its position, getting it into the “open” or “closed” positions is a bit unreliable.

         Anyway, have fun if you decide to try it 🙂

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3. asdf2304 03/06/2017 at 11:11

   it was very helpful!Thank You for editing cause I saw this only for education set…!

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4. Bill 07/03/2017 at 11:09

   Thanks for taking the time to publish these plans and idicate which parts are needed in addition to the EV3 Basic Set 31313. Very helpful.

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5. Rudi 15/02/2017 at 07:07

   I have to say, this has been the most frustrating robot I have ever built. Your instructions are a mess! Many of the pieces I put together, had to be taken off, constantly, because you “forgot” to put another piece on the inside of said part! Please, learn who to write proper plans / instructions! See how the Lego educational documentation was laid out and learn from it.

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   1. Bjoern Post author17/02/2017 at 01:54

      Hi Rudi,
      thank you for your feedback. I don´t have a problem with critical comments but I am pretty sure you missed this statement in the article:

      The instructions were automatically generated by LEGO Digital Designer (LDD) and are far from being perfect. I suggest you download LDD and view the model there.

      …

      You simply can´t influence how the LEGO software generates the steps in the manual (I have used LDD 4.3.0). I am not sure how LEGO creates their manuals – I am pretty sure they don´t use LDD 😉
      Therefore my suggestion to open the model in LDD directly. There you can move the assemblies around or take them apart and see how they were put together.

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6. ripripla 27/11/2016 at 22:46

   Can you do something similar with Znap and Puppy?
   Thanks.

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7. Brian King 04/09/2016 at 05:43

   The is great, thanks! The only major problem I encountered with the LDD file is that it appears to require three Z12 gears, while the home kit only comes with two.

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   1. Bjoern Post author17/02/2017 at 02:12

      It seems you are right. I guess my set came with an extra Z12 gear.

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8. Alfredo 06/05/2016 at 17:54

   Hi!

   Where can I find the program to upload into the LEGO Intelligent Brick?

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   1. Bjoern Post author17/05/2016 at 01:42

      I have lost the code the last time I reinstalled my PC. I plan to publish a new version of the code some time…

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