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Thread: R2Talk2 - a talking robot with rotating head

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    R2Talk2 - a talking robot with rotating head

    Hi, i'm new to the forum (this is my 2nd post) so please don't be too harsh if I mess this thread up or make a mistake in forum etiquette.

    I've been making a little robot just out of bits and pieces and a TalkBot robot controller and a couple of wheeled servos. I hope it doesn't look too amatuerish compared to all the highly polished expert robots in the projects section! You guys are amazing.

    This is R2Talk2.
    He's a talking 2-wheeled robot, with a rotating head (like R2D2).
    He's a bit over 150mm (6") in diameter and about 220mm (9") tall.
    I wanted to throw him together pretty quick mainly out of junk, to see if I could get a fun robot for very little cost.



    Hmmm, let's see if I can get the pictures working!
    Last edited by Macro Man; 09-08-2009 at 01:30 PM. Reason: darn images broke

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    Re: R2Talk2 - a talking robot with rotating head

    Trying full sized image;
    http://forums.trossenrobotics.com/ga.../1/1/back2.jpg

    I wanted to make something with the new TalkBotBrain controller from
    BlackRobotics. This little controller is a bit limited because it only
    has 2k of onboard ROM and a handful of input/output ports, but it does
    have 2 cool features out of the box;

    1. It talks! With any words/sounds I want. Yay.
    2. It drives up to 8 servos automatically.

    These parts came from BlackRobotics.com
    * TalkBot Controller PCB and 40mm speaker
    * 2 HITEC rotation servos
    * 2 servo->wheel hubs

    Other bits from my junkbox;
    * 1 HITEC HS422 normal cheap servo (for head rotation)
    * Sharp GP2 sensors Infrared distance sensors (2 ranges; 150cm and 80cm)
    * Toggle switch, wires, few LEDs etc

    Stuff I had to buy;
    * 6v 1.3Ah battery
    * 2 Tamiya fat racing wheels
    * Red plastic $2 bowl from supermarket

    The idea was to see if I could build a bot that was fun and also
    practical from the most basic setup, ie a TalkBot brain and a couple
    of servos. The brain and wheel servos were a gift from a friend at
    BlackRobotics and I had a junkbox head turn servo and some sharp
    sensors kicking around , so the only real cost to me was the battery,
    wheels and red plastic bowl, under $20 total. Total cost would be
    a bit over $100 if you had to buy all the bits I guess.

    Design Goal.

    Well I knew the robot would talk, but I wanted to bump up the cool
    factor. So I went for the rotating head!
    This was an easy one since the
    controller would drive the servo directly and it would also make
    good use of 1 or 2 distance sensors as he can "scan" the
    surroundings and get his bearings. So he can look around and say
    "whats that?" or "who's there??" then trundle over to investigate
    the thing he saw... You get the idea.

    Some fat wheels to look cool, I really don't like those skinny
    things normally attached to servos. These Tamiya ones are great.
    Very grippy and air filled so they are a bit like suspension.

    And finally some practicalities. A castor that will work on carpet
    and tiles and also cost nothing, a flat smooth base so it won't snag,
    some covers so he looks like a real robot etc.

    And so R2Talk2 was born... Or is about to be born.

    http://forums.trossenrobotics.com/ga.../1/1/back3.jpg

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    Re: R2Talk2 - a talking robot with rotating head

    Hmmm, need to try those large images again;




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    Re: R2Talk2 - a talking robot with rotating head

    Hi Macro,
    Welcome to the forum.

    I like this little guy, he's cute. Good job.

    Gary
    Team Maggot---Mechs. "Bheka" (retired), "Maggot Mk.3(A)"
    " Keep your stick on the ice ".... Red Green

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    Re: R2Talk2 - a talking robot with rotating head

    The Rolling Base Design.

    There is a flat base plate, but instead of mounting the wheel servos
    to the base plate the base plate supports 2 vertical plates,
    and the servos are just screwed into the vertical plates. A top plate
    secures the vertical ones so it makes a basic box skeleton out of
    4 plates. With 8 big wood screws it's very sturdy.



    I used 10mm nylon cutting board for the vertical plates. This was
    a supermarket cutting board I had chopped up for something and
    had enough left to make the 2 vertical plates. It's very stiff and
    easy for screwing. The main screws are just some countersunk type wood
    screws. 8 small wood screws hold the servos in. The other small
    screws are junk that was pulled from old VCR's etc I like to keep
    the pretty coloured ones.

    For the top and bottom plates I didn't have enough chopping board
    and it would have been a bit thick anwyay. I found some old 6mm
    white perspex (acrylic) from an old sign or something. It had
    holes drilled in it and was a bit messy but most of that won't be
    seen in the finished bot so it was good enough.

    The size of the bot was based on the nice red bowl I found in the
    supermarket. This bowl had a flat top and totally flat conical sides
    both are handy features. I designed the top and bottom plates
    to suit that size. The wheels were moved forward a bit from true
    center, making him more stable, likewise the castor was moved
    rearward as much as possible.

    The octagonal shape was changed a little to suit the new wheel
    positions and still match the head bowl. And maybe look nice.

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    Re: R2Talk2 - a talking robot with rotating head

    Quote Originally Posted by gdubb2 View Post
    Hi Macro,
    Welcome to the forum.

    I like this little guy, he's cute. Good job.

    Gary
    Hi Gary! And thanks man!

    I wrote up some texts last night to go with the pictures, and i'm still trying to work out the easiest way to cut and paste it into the thread. It wouldn't let me edit post2, something to do with the html image links I stuffed up probably.

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    Re: R2Talk2 - a talking robot with rotating head



    The plates were cut on a bandsaw (some bits with a hacksaw) and
    shaped up with files and the gaps kept small so it wouldn't snag
    too much on carpet or wires on the floor.

    The castor was my own design, I didn't want the cost or size of
    an omni wheel or the snagging hair-grabbing problems of the
    small castors. This "ball" system worked really well.
    I cut a hole in a ping pong ball and just filled it with some
    epoxy stuff to make it a hard solid ball. Then drilled a hole
    through it to spin freely on a 6mm steel rod that came from an
    old bubblejet printer. Once I could hold it central on the rod
    I also ground the 2 sides of the ball flat to make it more like
    a wheel.



    There is another bit of nylon board holding the 6mm shaft for
    the castor. This is just clamped down with 2 screws to the bottom
    plate and can be removed easy for service and cleaning. I set
    the height with some cardboard to adjust it a fraction to make
    the bot level.

    The castor works perfectly. It rolls in forward and reverse,
    and when turning it just slides it's real slippery on carpet and
    even on hard floor and tiles.

    I cut a recess out of the back vertical plate to hold the battery
    weight so it only needs a little clamp to secure the battery to
    the plate. A 6v sealed gel type battery was chosen because it's
    cheap and neat. The TalkBot has a nice low-dropout 5v regulator
    and will work fine from 5.1 volts up, and the servos can run
    direct from the 6v battery that is normally about 6.5v in
    operation. Also the servos are efficient, under 200mA to move
    the whole bot and he doesn't move all the time so a 1.3Ah
    battery will give many hours of life between recharging.



    The TalkBot brain was added and I made a switch and LED bracket from
    bending a little bit of alloy sheetmetal. I plugged in the 2 wheel
    servos and with a bit of quick C programming R2Talk2 started
    doing a little forward-backward-turn dance on my living room floor...
    He's alive! Yay.

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    Re: R2Talk2 - a talking robot with rotating head



    Rotating Head Design Spec.

    I wanted to get this right. The head should be able to do the
    full 180' (half turn) that the servo can do, but be smooth
    and not have cable problems. The solution was pretty simple
    with just a saddle clamp to secure the cable and some spiral
    sheath to make the cable slippery. It works well, mainly
    because the top plate is flat and smooth so the cable can
    slide as the head turns. The cable gets a bit tighter as
    the head turns 90' left, and it gets a bit looser as
    the head goes 90' right (see above).

    I soldered the cables direct to the 2 Sharp sensors, this
    gave a bit more room and only needed 4 wires from the brain
    to the sensors; +5v, ground, signal1 and signal2.

    The whole servo to head-bowl setup looks simple but I spent a
    bit of time thinking it through before building it. The
    overall height had to be right so the bottom of the headbowl
    sits right on the top plate and the entire outer rim of the
    bowl acts like a bearing for strength and looks.

    The other thing that I really wanted was for the head rotate
    and IR sensors to be fully functional with the head bowl removed.
    This means he can be tested and inspected when operating
    the head or even operating the whole robot without his "dome".



    The 2 servo risers were cut from the nylon board again. They
    are positioned on the top plate so the shaft axis of the servo
    is the center of the bowl, and the whole bowl centers nicely on
    the top plate.

    Some thin alloy sheet was cut to size and bent (I just used
    a bench vice and some wood to bend it). This holds the 2 Sharp IR
    sensors. Just a standard plastic servo horn connects the alloy bracket
    to the servo, and another bit of white plastic sets the height
    and gives something thick enough for the screws to bite into.

    I added a donut of soft green foam rubber around the servo
    horn. This gives some extra friction and stops the head from
    jerking when it turns because it was turning too easy and the
    extra mass of the whole head was causing an oscillation sometimes.
    With the green foam and a software tweak it now turns super
    smooth and steady.

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    Re: R2Talk2 - a talking robot with rotating head



    Testing the 2 Sharp IR sensors. He has a good field of vision,
    the forward facing sensor is the 150cm type, so he can see
    any objects up to 4 feet away in his 180' scan field.

    I ended up pointing the other 80cm range sensor down at an
    angle. This means it will only detect vertical objects in close
    range 20cm or so (8") BUT it will find things on the floor
    at about 30cm range (12").

    The 2 sensors work well as a team. The longer range sensor is
    perfect for finding walls, chairs etc for navigation, it will
    easily see a vertical pencil at 3 foot distance. Quite impressive
    especially coupled with the ability to slowly scan the head
    and determine an accurate angular position to the object.

    And the closer range sensor tilted downward acts more like an
    emergency "bumper", it tells R2Talk2 if something has got too
    close like a small object on the floor that might represent a
    hazard. Like a sleeping cat's tail... Very hazardous!



    The head cover bowl works pretty good! A big square hole
    was cut in the front of the bowl to fit the sensor array.
    The head cover bowl quickly slips on, right over the sensor bracket,
    and just one black screw on top secures the head bowl and makes
    R2 look like... Well like an R2.

    That's about it for now.

    At this point i'm quite happy about how R2 is shaping up.
    He has good mobility, trundling easily over all my household
    flooring including doormats etc.

    Construction was kept real simple and easy to do again,
    the 4 body plate construction works good and can be operated
    independent of the covers and likewise the head rotation
    assembly works great for such a simple system. Everything
    is rugged and should be reliable. This method of construction
    might even work for a larger R2 type robot, I've been eyeing
    off a nice 250mm plastic dome bowl...

    His head rotation is smooth and/or fast. Sensor performance
    is good. So little R2 is no longer lame or blind. But he's still
    stoopid (no AI programming yet) he's still mute (need to load
    some voice recordings in him and connect his speaker) and
    worse still he's totally nekkid!

    Next job is to cut some outer cover panels and give little R2Talk2
    some clothes, and a front panel sounds like a good place to
    mount that 40mm speaker.

  10. #10
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    Re: R2Talk2 - a talking robot with rotating head

    That looks cool!
    Just another great example of what can be built at home without much $!

    BTW, how did you attach the plastic boards together?

    Great robot!

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