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Dexter

An open-source, 3D printed, high precision robotic arm with trainability

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Dexter is an open-source robotic arm mostly made with a 3D printer. It uses 5 NEMA-17 stepper motors to control its 5 axes along with harmonic drives on 3 of them. We put quadrature optical encoders on each axis since stepper motors don't have encoders and they sometimes skip if not strong enough. Having these encoders allows the FPGA microcontroller on Dexter to poll the sensors fast enough and correct the motor's position in real time. Thanks to our gateware, we can poll each axis 5 million times per second, creating a 200 nanosecond feedback loop. Dexter is licensed under GPL3 so the design can be reproduced and modified at will. All of our files are on our OnShape, GitHub, and Thingiverse and a link to the building manual is in the build instructions.

Dexter is an open source, 5+ axis robotic arm. Its parts are 3D printed with PLA and held together with carbon fiber strakes for reinforcement. It uses 5 NEMA-17 stepper motors with harmonic drives on 3 of the axes. These don't have encoders and are prone to slipping, so we build our own optical encoders mounted on the axes themselves. We use 2 sensors with one of them 90 degrees out of phase so we get a quadrature encoder out of the system. Our software interpolates these values as sin and cos and allows us to measure each axis.

We use an FPGA to allow us to process the data from the encoders in real time. With our gateware, we're able to take 5 million measurements per second and get a 200 nanosecond control loop with the motors. This allows the motors to react when changes are detected in the optical encoder. One of our control modes known as "follow me" allows someone to physically control Dexter by touch without backdriving the harmonic drives (doing so wears them out and eventually weakens the integrity of the transmission.)


We wanted Dexter to be easy to program to someone new to robotics and a basic understanding of code, so one of our team members created Dexter Development Environment. It uses a modified version of JavaScript due to accessibility and it comes with documentation on how to program Dexter in DDE.

Dexter uses a socket connection for DDE, but that isn't the only thing that has used it. One of the members of the Dexter community has actually developed a Unity library for use with Dexter. Using follow me mode, you can actually connect move Dexter around in virtual reality to interact with objects. Touching one will provide haptic feedback in the physical Dexter. We think this was really cool because that opens the door for Dexter to potentially be used as a game controller.

  • 1 × Stainless Steel Tube Used as a shaft for a differential pulley
  • 2 × 5mm 16 teeth GT2 Pulleys GT2 pulleys made for use with NEMA-17 stepper motors. Used for differential pulleys
  • 1 × Haddington Dynamics PCB https://github.com/kgallspark/Dexter/tree/master/MotorControl
  • 1 × TE Part #2-179694-2 Used as an End Effector In/Out (EEIO) connector
  • 10 × 6P TE Part #215297-6 Used as a connector for optical encoder PCBs to the main PCB

View all 35 components

  • Haddington Dynamics Discord Server

    Haddington Dynamics07/24/2019 at 17:29 0 comments

    We've created a Discord server as a way to quickly interact with the team and the Dexter community. You can talk to other Dexter owners about your current projects and get help troubleshooting any issues you may have. Join here: https://discord.gg/YkfQRJa

  • Dexter HD Build Videos

    Haddington Dynamics01/23/2019 at 19:33 0 comments

    The Dexter HD build manual is now public. Instead of a book like last time, we went with a video series. Parts 1 and 3 aren't necessary for those who buy kits as those have been completed already. They're more for the people who are building their own Dexter HD from scratch. 

    The videos can be found in this playlist on YouTube: https://www.youtube.com/playlist?list=PLEJQ7hsad17fC2tqTDGNFI_LPk1kX2aE6

    The BOM for Dexter HD is also available for those who wish to source their own components. Keep in mind that it is still a work in progress from our older system for organization of parts, so some quantities of hardware may be incorrect. It can be found here: https://docs.google.com/spreadsheets/d/1tPxJF4zsaoBsXhz2b6sy5hTPxMfhjwwAfAAC_93CtzM/edit?usp=sharing

    We can't wait to see what you make!

  • Dexter HD

    Haddington Dynamics11/09/2018 at 22:42 1 comment

    We have begun to release the STLs to Dexter HD. A page on Thingiverse has been created where you can download the parts. There are likely at least a few parts missing, but we will be updating everything as we move forward. https://www.thingiverse.com/thing:3206154

    We are also currently creating documentation on how to build Dexter HD. It will be in video form on our YouTube page for all to view. We estimate we will be done with the series within the next two weeks and we are going to release all of them at once. 

  • Updated Print Farm

    Haddington Dynamics10/22/2018 at 06:22 0 comments

    If you follow us on Twitter, you may have seen that we have updated our print farm. We have 4 Markforged printers set up, 3 of them are Onyx Series while our first one was a Mark Two. We've been using their Onyx filament along with embedded carbon fiber in the Mark Two. Onyx is a filament created by Markforged that consists of chopped carbon fiber. This allows us to print stronger parts that have a higher melting temperature than PLA. PLA is a good material, but we can't leave a Dexter made of one in a car during the summer here in Las Vegas. We have before and it needed major repairs due to deformation.

  • Reconfigurable Gripper

    Haddington Dynamics10/20/2018 at 21:04 0 comments

    Using our new tool interface design, we have printed a reconfigurable gripper end effector. On the 7th axis, there is a servo for rotary power takeoff for a movable finger which works with a fixed finger. The end effector is removable so different tools can be used. We have already made end effectors for use with pruning scissors, tweezers, and a manual vacuum pump. If you want to build your own, the STLs are available on Thingiverse: https://www.thingiverse.com/thing:3166448

  • Development Branch on GitHub

    Haddington Dynamics10/20/2018 at 02:57 0 comments

    There is a branch on our GitHub repository called TDInt. It is the development branch for testing new things out in Dexter's firmware. One of the recent updates adds functionality for a new file type we call .make_ins. The new type allows for a list of instructions to be run from a single file. Dexter's "boot up dance" is now part of the autoexec.make_ins file instead of in DexRun.c. This allows anyone who wants to change what their Dexter does on boot up to do so without recompiling the DexRun software. This also makes it possible for to Dexter run tasks without the need of an external computer. Check it out here to learn more https://github.com/HaddingtonDynamics/Dexter/tree/TDint

  • Control of Many Servos

    Haddington Dynamics10/18/2018 at 21:29 0 comments

    While we were implementing the 6th and 7th axis onto Dexter, we realized that our FPGA servo control system is so fast, it should be able to operate over 200 servo motors at reasonable update speeds. We're not sure there is any application that could use that many, but we do know that it gives us a great amount of potential in regard to Dexter's end effectors. The Dynamixel servos can be daisy chained together using the included cable. We had already been using this method to connect the 6th and 7th axis, but if your end effector application needs an 8th, 9th, or couple hundred more, that can be done.

  • New Tool Interface

    Haddington Dynamics10/17/2018 at 22:06 0 comments

    We have developed a new tool interface for use with Dexter. It provides more interactivity with a pair of Dynamixel XL-320 servos as a 6th and 7th axis. The 6th axis acts as a wrist and the 7th is available to power a gripper or other end effector/tool. With their built in torque sensing, they can be back-driven like the rest of Dexter's axes. We are also working on adding a set of pogo pins to bring out signals and a tiny screen to display information and take selections from a user. https://github.com/HaddingtonDynamics/Dexter/wiki/End-Effector-Servos

  • Haddington Dynamics Wiki

    Haddington Dynamics10/17/2018 at 16:24 0 comments

    Dexter is a stunningly complex robot. Understanding how it all works just from the source files is nearly impossible. Our inhouse Technical Evangelist, James Newton, has been working hard to develop a centralized place for Dexter documentation. It has information on all things Dexter, from end effectors to gateware to DDE. If you want to understand how Dexter really works, please read the "manual" at: https://github.com/HaddingtonDynamics/Dexter/wiki And if it still doesn't make sense, raise an issue or ask us here. We could use help with the docs.

  • Automatica

    Haddington Dynamics06/01/2018 at 21:16 0 comments

    2018 continues to be good for Haddington Dynamics and we picked up seed investors.

    We will be exhibiting the remote control scaling system in Munich at the automatica show.  This along with the latest version of Dexter we call Dexter HD.

    Very busy times.

View all 13 project logs

  • 1
    Dexter Assembly Manual

    The link to the Dexter Assembly Manual is here

  • 2
    Wiring Harness Tutorials
  • 3
    Complete Schematic and all Design Files

    You can find a link to the complete schematic and STL files in the form of an OnShape model here.

    All other open source files can be found on our website: http://hdrobotic.com/open-source/

View all 4 instructions

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Madaeon wrote 04/22/2022 at 09:53 point

I am interested in building one. It can be the first version or the HD.

I saw a kit is mentioned, but it seems is not available anymore, at least, not on https://www.hdrobotic.com/shop, where prices start from 13.000 (ouch) and there are no kits listed.

I am wondering, has anybody built/ assembled one using just the info on github/thingiverse? Does it work, are all the parts listed, is the Bom missing something?

I would like to avoid starting ordering / making parts without any feedback on the feasibility of making it. Thanks!

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ScientificAmerican wrote 12/10/2021 at 08:18 point

Can I build a Dexter HDI now?

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James Newton wrote 12/27/2021 at 16:59 point

The HDI has NOT been fully open sourced. However, some of the changes from HD to HDI have been, e.g. the diff. It's all on the public github repo, especially under the wiki. The hardest parts are 1. getting the electronics (we keep hoping someone will layout an open source PCB, we make all the schematics available), 2. Getting the wave drives (email Harmonic) 3. Finding the chips, during the pandemic shortage. Honestly, it's a challenging built, but it IS still possible. 

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ScientificAmerican wrote 12/27/2021 at 17:37 point

Great! Maybe, I can help with the PCBA part. Is it the optical encoder or the Xilinx FPGA that needs to be layout? Also, the mechanical parts are the same except the Differential Joint, right? I only see HDI mentioned on the Differential joint page in the Github wiki. 

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James Newton wrote 12/27/2021 at 17:56 point

I'm replying to myself here because it's not allowing me to reply to you.

All the PCBs need new layouts. But the optical encoder is trivial, so I wouldn't worry about that. The FPGA is currently on one board (a MicroZed) and the Motor Control Board (MCB) plugs into that. One of the problems is that because of the way the connectors are setup on the MicroZed, most of the board space on the MCB is taken up running traces. The real solution is to re-design the MicroZed / MCB stack into a single board... or into an FPGA / Analog board with a connector on the bottom that plugs only the necessary signals into a Motor / Power board. We don't need all the stuff on the MicroZed, and if you keep all the signals we do need connected the same, the .bit file for the FPGA should work without modification (and you can't modify it... or rather... you can, but it would be really difficult). That is still a heck of a complex board design, because the MicroZed is a really tricky layout to meet all the requirements of the FPGA. This is not an entry level project! LOL. But it should be in the scope of medium to advanced open source boards. 

There ARE a few other (minor) differences between the HD and the HDI but a good mechanical engineer would see them easily, and the robot is still useful without them. 

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ScientificAmerican wrote 12/28/2021 at 11:53 point

Thanks for the detailed information! I have experience with the Altera cyclone FPGAs to control high-speed ADC, DDR SDRAM, and PCIe interface. I may just have the required skills for this design, although I never used a Xilinx FPGA. There are several websites related to this project, I wonder where should I start first. Should I start by building a Dexter HD, then upgrade it to HDI? Is the OnShape version most current? I also clone the fusion360 version HDI, but I think it's mostly outer shells. 

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James Newton wrote 12/28/2021 at 17:16 point

The big question is what printer you have available. If you have access to carbon fiber, the HD makes the most sense. If you have PLA, then you should certainly print the Dexter 1; it's a tougher build (lots of little bits to strengthen the PLA) but it's also more rigid (carbon fiber is typically bound in nylon and so it deforms) and perfectly usable. If you want, you could try the HD in PETG or a resin if you can print with those.  Don't get hung up on the idea that later versions are "better" they all have good and bad points, as I've indicated. 

If you just want to print one of the version, use the links to the STL files from the Hardware Wiki page. If you want to make design changes, OnShape is the only option. 

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ScientificAmerican wrote 12/29/2021 at 06:15 point

I have built a Voron2.4 350*350 recently, but I did not try anything but PETG with it. The reason I care about the version HD or HDI is that I plan to use it to perform some precision tasks. I read about the HDI on the official website, and find it quite enough for my future applications. But I can't find detailed info about the performance difference between HD and HDI, so I think I should try to build an HDI. 

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James Newton wrote 12/29/2021 at 16:56 point

The Dexter 1 is just as precise as the HD or HDI. They have a bit more load capacity, e.g. 2 or 3 kg (with counterweights) vs the Dexter 1 at 1 or 2 kg. Dexter 1 is stiffer, which means it can hold a precise position better.

Also, keep in mind the difference between accuracy and precision. Dexter is precise. It is only accurate /after/ calibration. I mention this because a LOT of people are confused about the difference between accuracy and precision. 

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marazm wrote 02/15/2021 at 21:22 point

Please show one video. Cut wood similar cnc but in 6D = XYZABC

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James Newton wrote 02/16/2021 at 04:29 point

Dexter doesn't have the stiffness required to cut wood. Polish, paint, burn, etc... would work. We've done laser etching. 3D printing has been on our todo list for a long long time, but we've just never had the time to do it. LOL. Should be possible. And... it should be possible to mount the extruder (or extruders) on a fixed external mount and then have Dex hold the build plate. That way, you can print up a face, then turn the print sideways and print off in another direction, avoiding supports.

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marazm wrote 02/16/2021 at 13:26 point

robot arm has many advantages but

but for it to be suitable for anything there has to be pressure. Cutting in wood (the simplest) is what illustrates how useful this tool is. arm must be able to control material cut, pressure, resistance 

unless it's just a gadget for the movie and not a tool

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James Newton wrote 02/16/2021 at 17:05 point

I guess pick n place machines have to cut wood? 3D printers have to cut wood? We can apply 3KG of pressure, but without /stiffness/ that will not correctly cut wood. We can operate a drill press, serve beer, load strawberry flats, dispense soft serve ice cream, do medical testing, tend other robots like CNC machine, or pressure mold, or 3D printer, and on and on... but sadly, since we can't cut wood, we are useless. LOL. Build a CNC machine or router for cutting wood. And Dexter can load planks, operate the CNC software, and remove the finished parts for you. 

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Lightning Phil wrote 06/04/2020 at 20:14 point

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cheese.amiller wrote 04/15/2020 at 22:10 point

what is the difference between the buyable one and this have you implemented any new ideas

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Haddington Dynamics wrote 06/04/2020 at 21:40 point

The Dexter HD simplified the build process and improved the accuracy of the original by reducing the amount of parts and glue needed for assembly.

The Dexter HDI reduced the amount of glue used even further in favor of bolts and threaded inserts as well as decantilevering the pulleys with some new parts. The code disks were also changed so that Dexter can achieve absolute positioning as opposed to the relative positioning that we've been working with up until the HDI. This is done by closing off some of the slits slightly and having the encoders monitor where those points are. 

We don't currently have a timeline on when we will be open sourcing the HDI, but it will be when we move onto our next version of the design.

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Ryanwallace18 wrote 01/05/2019 at 14:19 point

Most force/impedance robotic control systems measure torque to detect an obstacle collision. Does Dexter measure torque perhaps through the motor control circuit, or just use the joint position, or joint position rate of change to detect an obstacle? James, I noticed that you sell magnetic abolute position sensors on your site. The AS5047 gives you 16,384 counts per revolution at about 10-20khz. This is much lower than the one million CPR of your sensor, but was this not high enough resolution or fast enough to do force control?

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James Newton wrote 01/06/2019 at 06:15 point

First, my own site and encoders have nothing to do with Dexter or Haddington Dynamics. The AS5047 is 4000 CPR, not 16K. The sensor on the Dexter is very much NOT my design, it was developed by Kent, the principle designer at Haddington Dynamics. 

Dexter measures position only, but because it is so sensitive, it can detect forces like a cotton ball being dropped on the arm. 

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Ryanwallace18 wrote 12/12/2018 at 19:02 point

Has anyone implemented this on anything other than the microzed fpga? It's 5 years old and there are cheaper alternatives now. 

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James Newton wrote 12/12/2018 at 19:49 point

I think we would love to hear about alternatives which support the same general capabilities: Same FPGA size, 32 bit ARM core, Ubuntu, lots of IO. We've been talking to Avnet about the platform. 

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Ryanwallace18 wrote 12/12/2018 at 23:13 point

Will the .BIT file work on other xilinx boards or only the MicroZed?

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James Newton wrote 12/13/2018 at 21:05 point

I'm honestly not 100% sure. I'll have to ask our lead about that, but my understanding is that the .BIT file is designed for the chip used on the MicroZed, so it would work on any board that had that chip... and... that had the IO pins from the chip connected in the same way that the MicroZed connects them... so, technically "yes" but effectively "no". 

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Andrew Smart wrote 11/19/2018 at 06:59 point

I came here after receiving an email on the Hackaday prizes, and started researching. This project is fantastic, I am most impressed with the Dexter Development Environment (DDE).

I won't be building this till I've simulated my intended use (using the DDE and maybe FreeCAD [1]) and any cycloidal drive prototype stl's are released. Three harmonic drives at >$100 each [2] in addition to everything else is out of my budget/risk appetite. My personality is such that I'll trade time and labor to minimize expenses and optimize things, you learn more that way anyway, it is what I enjoy!

----------------------------------------------
Slip Ring
----------------------------------------------
8mm slip ring referenced on page 4 of assembly manual. Looking at BaseLite.stl, which slip ring fits over, diameter is 84.3mm.

As the large copper rings appear to be manufactured in bulk by punching/stamping copper sheet [3] (requires machining of stamp), the most cost efficient choice would be to choose some "standard" size that is already mass produced. Using the Conflat Flange (CF) 80 gaskets, used in the high vacuum industry, would be a good fit. 80 refers to the ID in mm, but rounded down, see chart [4]. CF100, with ID of 102mm, appears to be more commonly used/available. No CF80 on Aliexpress, but many Alibaba sellers. CF80 distributor on Ebay sells 2 for $20 [5], but the cheapest single CF100 I could find is $5.50, so...

I can see the assembly manual right now starts but doesn't finish the slip ring connection. Skimming through the videos/webinars I couldn't find directions for the slip ring.

----------------------------------------------
Carbon Fiber Parts
----------------------------------------------
Costs via DragonPlate supplier (for comparison):

1.5mm 4.4mm 705mm CF strake: $4.53 (.057" x .177" x 48") [7]
2.5mm 5.6mm 2652mm CF strake: 2x $8.67 (.092" x .220" x 48") + $4.77 ( .092" x .220" x 24")
3.2mm 12.6mm 2616mm CF strake: 2x $12.74 (.125" x .500" x 48") + $7.01 (.125" x .500" x 24")
5mm 20mm 321mm CF strake: $8.81 (.200" x .250" x 24")
6mm 8mm 137mm CF rod/tube: $5.05 (.315"OD x .239"ID x 24") [8]
1" CF Square Tube: $60.75 [9] (base arm)
.75" CF Square Tube: $49.75 [10] (forearm)

Cart total is $183.49. And shipping at checkout is "Shipping charges are calculated when order ships"... Would save some $ by using 1" tube for the forearm, but would have to change model.

----------------------------------------------
DIY Carbon Fiber Parts
----------------------------------------------
Making the CF strakes/rods from carbon fiber sheet and epoxy is an option worth considering. It looks to be lower cost and higher labor, but I see an opportunities like customizability and making a skin [6] using scrap materials. There are plenty of forum guides on making CF parts by hand, and in the future, by robot arm? :)

Carbon fiber fabric:
.23mm 1yd@$13.5/yd 36" [11]
.38mm 1yd@$17/yd 50" [12]

Layer 4 .38mm CF fabrics for 1.5mm thickness strakes, and etcetera:
.38mm*4 = 1.52mm
.38mm*6 + .23mm = 2.51mm
.38mm*6 + .23mm*4 = 3.2mm
.38mm*12+ .23mm = 5.02mm

Cured sheets would then be cut with table saw [13], or possibly by Dexter as he is so precise!

Only 4.05ft^2 of 12.5ft^2 .38mm fabric used; much to spare!

1" square aluminum stock (~$23 for 72" at US stores) can be the form for the square CF tubes [14]. And a 6mm aluminum rod (~$1-2) as the form for the CF tubes.

DIY Cost: $115.45 = $13.5 (.23mm CF) + $17 (.38mm CF) + $45 (Quart 820 Epoxy) + $15 (US shipping estimate) + $23 (1" aluminum stock, cheaper with a trip to the scrapyard)

Savings over DragonPlate and only using ~1/3 of the Carbon Fiber ordered. Downsides are less quality parts and no fancy cure process (e.g. curing oven to raise temperature resistance and mechanical properties [15]).

----------------------------------------------
FPGA
----------------------------------------------
MicroZed: $178+sh [16]

Might find a cheaper reseller or alternative, e.g. Xilinx Z-turn lite $117 [17] or $103 [18]. Would be nice to know what VIVA is compatible with, esp. considering this MicroZed can handle a lot more than Dexter's stock requirements.

P.S. I like your twitter quote of Stephen Hawking, we should be scared of capitalism, not robots. "If machines produce everything we need, the outcome will depend on how things are distributed."

[1] http://hdrobotic.com/dexter-community/#!/general:freecad
[2] https://hackaday.com/2018/08/24/a-peek-at-the-mesmerizing-action-of-a-cycloidal-drive/#comment-4976153
[3] https://www.ebay.com/itm/253978363132
[4] https://i.ebayimg.com/images/g/LE4AAOSw9~Rb6nKP/s-l1600.jpg
[5] https://picclick.com/2pcs-CF80-Copper-Gasket-New-Vacuum-Pump-Flange-173608218978.html
[6] https://github.com/HaddingtonDynamics/Dexter/issues/4
[7] https://dragonplate.com/Carbon-Fiber-Strip
[8] https://dragonplate.com/DragonPlate-Carbon-Tube-315OD-x-239ID-x-24
[9] https://dragonplate.com/Carbon-Fiber-Roll-Wrapped-Twill-Square-Tube-1-ID-x-1-ID-x-24
[10] https://dragonplate.com/carbon-fiber-roll-wrapped-twill-square-tube-075-id-x-075-id-x-24-3
[11] https://www.sollercomposites.com/Carbon-3K-Fabrics.html
[12] https://www.sollercomposites.com/Carbon-6K-Fabrics.html
[13] https://www.practicalmachinist.com/vb/general/cutting-carbon-fiber-plate-216679/
[14] https://www.bentrideronline.com/messageboard/showthread.php?t=3120
[15] http://www.shadowaero.com/COMPONENTS.htm
[16] https://www.avnet.com/shop/us/products/avnet-engineering-services/aes-z7mb-7z010-som-g-rev-f-3074457345635221615/
[17] https://www.aliexpress.com/item/XILINX-Z-turn-lite-ZYNQ-7010-ARM-Cortex-A9-with-FPGA-dual-core-Development-Board-Control/32836668246.html
[18] https://www.xilinx.com/products/boards-and-kits/1-pcz4jb.html

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James Newton wrote 11/20/2018 at 01:42 point

Hey Andrew, 
Nice work tracking all that down. We do have a partial BOM (linked from the repo) but it is a bit out of date and could certainly use to be updated. Let me know if you want to help update it. We did raise a help wanted issue about it.
https://github.com/HaddingtonDynamics/Dexter/issues/34
I've made that google sheet "Anyone can comment" so if you want to leave notes on it, go for it, and if you want to edit, just ask me.

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James Newton wrote 11/20/2018 at 01:59 point

Andrew, true confessions here: We've all disabled the slip rings on our robots... they just are NOT reliable and they cause so many problems with reliability that we gave up on them. If someone out there that can make a reliable slip ring, please let us know. Anyway, the robots typically don't need to spin around for the bulk of the work they do is all in the same quadrant. 

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James Newton wrote 11/20/2018 at 02:48 point

As I understand it, Viva is a high level design tool so it's compatible with any FPGA that we can get an accurate descriptor... file... format... thingy... for. I'm not the expert on that so I'ma shut up now. 

What I AM an expert on is firmware, so I'm starting work on a code only (no FPGA) version with a lasercut encoder which should be as accurate (or better with a good laser) but much much slower. It's designed for human input, so you can make a non-powered "arm" with this, connect to a Dexter arm somewhere else in the world, and control it by moving this low cost local "arm" encoder around. Please consider being involved:
https://github.com/JamesNewton/HybridDiskEncoder

I'm hoping we can use the Cypress PSoC chips because they have a good 32 bit ARM core, enough memory to do ATAN2 (which is the necessary math), they have an onboard programmable analog front end, AND... they have a little FPGA which we may be able to use in the future to increase speed. 

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Andrew Smart wrote 12/13/2018 at 17:49 point

Now that I look more, I think the MicroZed looks quite interesting. I'm sold after seeing the MicroZed chronicles, seeing OpenCV works with it, and utility for other projects.

I think it best for now I offer suggestions/ideas where I think I may have something to contribute. I hope I can get through other projects and start building Dexter, though there is much preliminary reading I must do. 3kg payload, very impressive!

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James Newton wrote 12/13/2018 at 20:11 point

Andrew, don't hesitate to ask if there is anything we can do to help you get started building a Dexter.

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