Loki Electronics

This page describes Loki’s electronics.  My other robots use similar, with variations.  So, most of the core info is here, but there may be details specific to each robot on its design page.

All of my robots use a main processor (laptop or PDA/Phone) for the higher level software, and a microprocessor for sensor interface, and often motor or servo control.  Loki has a laptop embedded in his chest that communicates via USB to various electronics.

For the MicroProcessor, I have been using a PIC-based Mark III controller board, which used to be available here, but I have heard may not be available any longer.

Also, I found I this cool site for making PCB boards,  PCBWeb. It looks really good!  Let me know if you’ve tried it!

1/15/2013 Update!   I finally moved to Arduino!  See Arduino section below.

 (click on pictures for larger view)


 Loki USB Connections

Sensors and Control Block Diagram


Wiring Diagram

PIC Interface Board


PIC I/O Expansion Board


Head and Arm Boards


Power Distribution


Arduino Robot Interface Shield

Arduino Interface Schematic

Arduino Board layout, using a proto shield

23 Responses to Loki Electronics

  1. Robert H. Zeiler says:

    Great job with LOKI. I was wondering if you could share how you were able to coordinate LOKI’s arm/hand location with the vision system?

  2. dshinsel says:

    Hi Robert,
    The Kinect sensor code creates an XYZ point cloud of everything it sees. the function “FindObjectsOnFloor” uses this data to identify objects of interest. Then in ArmControl.h” there is a function called “CalculateArmMoveToXYZ”. For pure vision (which I don’t rely upon as much, since I added the Kinect), the camera can be pointed with the function in HeadControl.h called “LookAtXYZ”. The Behavioral module Calls these functions to guide the arm to pick up the object. Note that XYZ maps as follows: Y= distance in front of robot’s front bumper. Z= height above ground, X=distance Right/Left of centerline (Left is negative).
    Hope this helps!

  3. Lloyd Cooper says:

    You may want to check out http://www.EZ-Robot.come

  4. Vito Pulpito says:

    kinect when you connected to the PC you had problems?

  5. Laura Lemmons says:

    Nice going on LOKI!! He’s intelligent, more intelligent than I thought. It must have costed alot to build him, but hey, a robotics engineer can have some fun can’t they?

  6. Pingback: » Loki: a Complex Bot

  7. Gus says:

    Hey Dave, there are two specs on your site that are conspicuously absent! 🙂 I was curious as to the spec of the laptop you are using. I understand that Kinect processing is quite intensive. Before I order a nettop for my robot, I wanted to know what you had under the hood…

    Also, batteries! I find that the vicious circle is: getting bigger batteries means more weight, which means bigger drive motors, which means bigger batteries! What are you using in Loki? (If you don’t mind 🙂

    • dshinsel says:

      Hi Gus,

      I’m currently running an 11″ Dell XPS with Intel Core i5. (3rd generation)
      The newer 4th generation will give longer battery life.
      I picked the Dell because it fit the space I had, but any Core i5 or better should be fine

      Some suggestions:
      Atom processor not quite powerful enough. Core i3 *might* work, have not tried it.
      Plenty of memory – go with 4 gig of memory if possible
      Use Solid State Drive (SSD) – significantly improves boot time and battery life

      For my next robot, I think I’ll go with a touch screen laptop or tablet (maybe one of those new “detachable” laptops). Seem like a good form factor for mounting options.

      The laptop runs on it’s own batteries, which is where a newer laptop really helps give longer run time.
      For the rest, I’ve been using a Lead Acid non-spillable (Werker 18A 12v) + 6A 6V. I use both to get enough voltage to drive a 12v regulator for the Kinect and other devices. The problem with Lead Acid is the voltage drops as the battery discharges, so you only get about half the actual rating. I recently got a huge 20A 12V Lithium, and that lasts much longer. Lithium batteries are expensive, and I was worried about fire (LiPo can be dangerous). I found the newer Lithium-ion Iron Phosphate (LiFePO4) batteries are much safer, have great run time, and are MUCH lighter. The only down-side is the cost. They are pretty expensive. One I like in particular is STARK POWER Again, pretty expensive, a 20A Lead Acid is about $70.00 and the 20A 12V is over $200. Also, make sure you buy their charger (price is pretty low for that). Standard lead acid chargers won’t work.

      • Gus says:

        Dave, thanks for such a comprehensive reply. I think that your projects serve as fantastic inspiration, fuelling the imagination of makers all over the place… but on top of that, we are all really grateful that you take the time out to help out budding builders. I hope to one day be showing you pictures of MY build! Thanks again.

  8. Rick says:


    Did you happen to get any good photos of the underside of the arduino shield? Would like to see how you soldered / routed your connections.


  9. Gus says:

    Dave, I was going to email you, but having discussions on the site might help others… You mentioned some limitations from the laptop approach – limited battery life, necessity to run an 18v supply in order to power the Kinect etc. I have been thinking about how to address this. I was thinking about using a low power mini itx board, (I don’t want a on-board screen, they use a lot of power) with a car to atx power supply. That way it can run off the main 12v power supply, and also output regulated 12v rails for the Kinect. Check these links: http://www.jetwaycomputer.com/NF9G.html and http://www.ebay.com/itm/M4-ATX-Wide-Input-Intelligent-DC-DC-Power-Supply-Car-PC-/200477704857?pt=PCA_UPS&hash=item2ead670299


    • dshinsel says:

      Good idea, but here’s an even easier option. Intel has a new product called “NUC” New Unit of Computing. It’s a small computer that runs on 12v. I have one that I recently installed into a new robot, and it is GREAT! It boots super fast (can be configured to boot when power applied), and great on battery ( I’m seeing typically about 1 amp at 12v!).

      Just Google “Intel NUC”. Note that most configurations do not include the SSD (Solid State Drive), wireless card, or memory, you have to add those depending upon the size/type you need. And make sure it’s “4th generation (Haswell), much lower current draw / better battery life.

      Let me know how it works out!

      — Dave Shinsel

  10. Mohamed says:

    Hi Dave I am ney in robotics as I am 11 years old I want to ask you a few questions please email me at Mohamedrahimtola@gmail.com

  11. jm.feltri says:

    je suis Français j’Ador les robot mon petit fils aussi qui a 10ans je voudrais faire le même pouvez vous m’envoyer plus de détaille je serais très reconnaissant

    • dshinsel says:

      RE: “I am French I Ador the small robot my son also has 10 years I would like to do the same can you send me more details I would be very grateful”
      Glad you like the robots. All information is posted on this website. Let me know if there is something specific you need! I suggest you start your son with “Lego Robotics”.

  12. Mohamed says:

    I know it will be hard to change now but if you visit ez robot.com they have a product called ezb it is like an arduino but way easier to program and you can also use C++ etc you will have more features in you robot and the community forum has some projects that people have done there are amazing

  13. trevor says:

    hey dave its awsome you switçhed to arduino mega. did you get a chance to take a picture of the arduino shield from the bottom?

  14. sean says:

    hey dave can you saw me how to make the loki one head the frist and how to make loki talk and his software pleace on cd

  15. Cristian says:

    My name is Cristian, I’m from Rosario – Argentina and one of my hobbies is to build robots with recycled materials, use as base element aluminum, their work is sensational, I follow the progress of Loki, love that robot, I congratulate I have shown her videos to my friends in the robotics group were surprised, Greetings Dave congratulations on his inspiring work!

  16. Danny says:

    Hi Dave

    I have a question about Loki, I and getting a blue disable on the head dynamixel servos. cannot enable them. what can I do to fix this problem?

    thank you

  17. Owen says:

    Hey Dave, sorry about the website. I’m going to TRY Ros on my Pi2, if it doesn’t work I’ll try Pi3, and then NUC.

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