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Thread: New Member

  1. #1

    New Member

    Hello Everyone,

    I am new to the forum. I am an Instrument/Electrical Technician at a Power Station in Virginia. I am 48 years old and enjoy tinkering with electronics. I have been fascinated with robots since I first saw the movie Forbidden Planet with Robby the robot. I've always wanted to build a robot. When I was young I had all the time in the world and no money. Now I have a little money and no time. Oh well, I have finally gotten started. I now have the skills and tools needed to build my very own robot. And what did I do? Start small and simple....noooo. Large and complicated. It has now become a midlife crisis. I must finish this! The robot will be called Magnus. He is approximately 6 ft. tall and already weighs about 190lbs. He has tank tread drive using two wheelchair motors. He is similar in appearance to the 1960's Lost in Space robot B9 (only in certain ways). I used a clothes dryer drum for the torso and various other everyday items for most of the remaining parts. He is still in the rough, unpainted stage of construction so don't laugh. Lots of finish work to do! The arms have been the hardest part so far. I am still having difficulty figuring out how to remote control everything. That's where I hope you all can help. Here is the link to my Blog. Let me know what you think www.r-gordon.blogspot.com

    Rex

  2. #2
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    Re: New Member

    Wow, that is huge.
    I most certainly am not the one to help you but it looks great. I'd love to see footage of it up and running once you're at that stage. Must be loud?


  3. #3
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    Re: New Member

    Welcome RGordon to this forum, WOW very impressive first time robot, As a joiner/cabinate maker i love your nice woodwork and in particular your neat wiring. Also love tank track type robots, Have a couple myself but not that big lol. love to follow this project with great interest. good work.
    People yearn after this robotic dream, but you can't strip your life of all meaning, emotion and feeling and expect to function.


  4. #4
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    Re: New Member

    Hi RGordon! Welcome to the forum.

    That's mighty fine looking handy work you have on the go.

    What problems have you been having with the arms?
    What sort of remote control would you like to have? RC? Game pad? Computer? Other?

    What are you using for the head? Looks great!

    I can't wait to see/hear more.

    Cheers!

  5. #5

    Re: New Member

    Hello,

    Thanks to all for the nice comments.

    The arms have been my biggest problem so far. With a robot this size you need high torque gear motors. Servos are just to wimpy. You can get servos with lots of torque but they cost far to much for me. Project Magnus is already turing into a money pit. Also, I am better with electonics than mechanical stuff. But, I'm gradually figuring it out. The elbow is the hold up right now. I need a motor that is strong enough to lift the weight of forearm and the claw assembly but, not so big in physical size so it will fit inside the 5" rubber duct that is the arm covering. The first thing I learned was that it needs to be a worm gear drive motor. The first motors I tested were standard gear motors and the weight of the forearm would cause the motor to turn when power was not applied then the arm would droop. The other thing that bothers me is there is no feedback to let me know what position the arm is in other than what I can see from the wireless video I plan to install. If anyone knows of a good low cost method of sensing joint position please let me know. I would ultimately like to be able to control the arms using some type of wireless joystick method. Also if anyone has any info on this I would appreciate it. Right now I will just be using the two "Cold Fusion" 12 channel remote controls I purchased off of ebay. These are just on/off relays. Their range is around 1000ft. I would like to share my plans and ideas for arm design if anyone is interested. Please see also my latest new thread concerning the wireless remote control questions.

    Oh, BTW, the bubble head is a replica of the one used for the robot from the 1960's Lost in Space robot B9. If you want one, I can point you to the link. They are expensive though at $360.00. But it just so cool I could not pass it up. I have been searching for years for the perfect head for my robot.

    Thanks,

    Rex
    www.r-gordon.blogspot.com

  6. #6
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    Re: New Member

    Hi RGordon,

    How many degrees of freedom were you thinking you'd like to have in the arms?
    How functional did you want the arms to be? Do you want to be able to lift things, or just flail them about while yelling "Danger, Danger".

    You might want to consider a simple pulley system for elbow, which would allow you to mount the motor in the ample chest space. Then the 5" clearance would be less of an issue.

    I'm definitely not the best person to be suggesting servos, but the higher end Dynamixel servos (available in the Trossen Robotics store!) might be beefy enough for your needs. The definitely give you position/load information though. Especially in conjunction with a pulley, at least for the elbow.

    Cheers!

  7. #7

    Re: New Member

    Hi kamondelious,

    The arms have a shoulder, elbow, wrist and claw motor. They just need to be able to move (flail) about for now. This robot will mainly be used to kind of put on a show. I would like to take him to places such as schools and special events to help get others interested in robot building. The plan right now is for me to control the robot from a nearby hidden location via wireless control and wireless video and have an assistant stay near the robot to interact with people, crowds and such. I wish I could build the arms strong enough to lift a few pounds of weight but, I will have to live with the way they are now. Just don't have that kind of money to sink into it. As long as they look cool I'll be happy. It may surprise you that there is actually not a lot of room left inside the torso due to the rather large shoulder motors. I have entertained ideas of using sheathed cables like the ones used on bicycle brakes or the speed adjust on a push mower and have a linear actuator inside the torso. I will take a look at the servo you mentioned.

    Thanks,

    Rex

  8. #8
    zoomkat Guest

    Re: New Member

    You might want to look at using linear actuators for operating the arms. They can be configured to operate as servos if needed so they can be positioned as desired.

    http://www.firgelliauto.com/

  9. Re: New Member

    Hi RGordon: I have been working on many size robots and I also have one that is 6 ft tall also. I use a forklift type arm. I don't know how big your motor that you need can be. I used a wheelchair motor in the arm and you can get both things you want. The brake in the motor can hold an arm in place without the need for power. Also it is easy to put an encoder wheel on the back shaft of the motor so that you will know where the arm is at all times. I may also be able to help you with the remote control and brain of the robot. I have been working on it off and on for about a year. (I can't stay with a big project for too long!). It uses two PDAs for a two way RF link. The PDA in the robot end will be able to control 8 motors with feedback from 8 encoders, 12 analog inputs, 15 High Low inputs used for limit switches. It will also be able to control some on off outputs and servos. The PDA for the human will give you the feedback from the sensors on it's display. If I don't get side track again I should have it done by the end of Feb. I will post it to my site when I get it done.

    Al http://diyrobots.webng.com

    P.S. I don't know what I will charge yet, but it will be less than $200.

  10. #10

    Re: New Member

    Hi Al197,

    Thanks for the reply. The arms have to fit inside a 5" flex ducting so a wheelchair motor is to big. I have not found any other motors with a brake that will fit. (forever searching) I have tried several ideas to make my own brake but none have worked. For now I am trying to come up with another design that is lighter. There is one other idea that I found that may be a way to simulate servo-like control of a large DC gear motor. It involves using the feedback circuit from a servo but replacing its motor circuit with a higher power H-Bridge and relocating the feedback potentiometer to the arm joint.

    For now however, my focus has shifted back to the remote control system. I am waiting for a "TTL to RS-232" converter cable to see if will remedy the problem I outlined in the previous posts.

    Rex

    "Skill is merely focus. When focus is achieved, you need only release it."

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