Saturday, August 9, 2014

Carl v4 - Carl goes for a ride!

Carl continues to be a hit, but for the last two years I've really been wanting to make Carl mobile.  Standing in one place, waving and giving out Play-Doh is getting old (at least to me).  So I've been looking for a Power Wheels type of vehicle that Carl can ride.

I finally found this electric trike back in February at a yard sale for $3.  What a deal!  It had no battery.  The switch was broken.  The paint was scuffed.  But it was everything I needed and just the right size and after all for only $3 it didn't even matter if the motor worked (which it did)!

I disassembled it completely and cleaned and repainted all of the plastic parts.

Here's what the frame of the trike looks like.  As you can see the steering is very simple.

I needed some way to connect a servo to the steering column so I built a bracket from wood to hold a servo.  My initial mechanism use a pin in the servo arm passing through a hole in the steering bar to turn the handlebars.
 This worked but it wasn't very elegant.  I ended up using my PrintrBot Simple Maker's Edition 3D printer to print a gear that fit around the steering column and a gear that fit on the servo.
I printed a gear to slip over the steering column and another gear to fit the servo.

My printer won't print fine enough to actually fit the splines of the servo.

 So I cut down a servo horn and epoxied it into the printed gear using JB Weld epoxy.

Here's the final steering mechanism.
Next post, the motor controller...

Monday, October 8, 2012

Carl v3 - Halloween 2012 - "Let's give Carl a hand!"

Carl and Me Last Halloween
Let me tell you!  You want kids to enjoy Halloween, just give them Play-Doh!  The tiny Play-Doh Party Pack cans were a huge hit last year.  (see last year's blog entry)

I would tell the kids they had to ask Carl "trick or treat" if they wanted something.  Carl would make some noise and then drp a Play-Doh can into the palm of his hand.  I had numerous kids look at me in amazement and ask, "Can I really have this?" 

Carl ended up giving out over 120 cans of Play-Doh that night.

So, for Halloween 2012 how am I going to top that?  Let's give Carl a hand!  Really!  If his right hand is giving out Play-Doh, let's have his left hand wave at the kids.

Here's my first test at just building a finger from PVC and one servo:

After 7 months of work testing variations of the first finger I ended up with a full hand:

I learned some important lessons.

- Fishing line loves to get tangled.  Just one line crossed over another will bring everything to a grinding halt.  That's the reason for the plastic tubing on the arm.  Running the control lines through the tubing keeps the lines from crossing and getting jammed up.

- There are two lines per finger in a push/pull configuration.  If you look closely near the servos you'll see an eyelet in behind each servo.  The line the close the finger loops through this rear eyelet effectively reversing the action of the servo.

- These are standard Futaba 3001 servos however they really aren't strong enough.  It would work much better with heavier duty servos.

- Solid copper wire makes really good hinges.  Each finger joint just has a single loop of solid copper wire through it and twisted closed to make a hinge for the joint.  Very simple and effective.

- PC Power Supplies (bottom right corner of video) are CHEAP!  I got this mini-ATX power supply from Tiger Direct for about $10.  It supplies lots of amps at both 5 & 12 vdc.  Great for operating the servos and the Arduino Uno computer.

- the Arduino UNO micro-controller can't be beat if you need an easy to program controller for a small number of servos.

And here's a video of Carl in action waving at the kid(s) and giving out Play-Doh:

Monday, October 31, 2011

Carl v2 - Halloween 2011

Letting Carl sit around and give out candy to the kids was good enough for last year, but this year I'm going for something a little more exciting.

While perusing Costco I happened to see 80 packs of "party size" Play-Doh for $20.  I immediately  bought two packages (160 cans) and decided Carl was going to give out Play-Doh this year!  At the time I had no idea how I was going to accomplish this, but I knew I'd figure something out.

The next day it was off to Home Depot with a can of party size PlayDoh in my pocket to brainstorm a solution.  What I found was PVC pipe the perfect size for holding the party size Play-Doh cans.  In Carl's arm I can stack about 25 cans.
Now I just needed a way to dispense them one at a time.  I decided to use a solenoid I had lying around to pull a pin that would hold the stacked Play-Doh cans in the arm.  I figured if I pulsed the solenoid fast enough I could time it to release just one can at a time.  It turns out you have to be faster than a human's reflexes to do this.

I ended up using a PICAXE microcontroller I happened to have sitting around and built a small circuit with a relay so that when I pushed a button the PICAXE would pulse the relay fast enough to pull the pin and release only one can out of the arm.  See the video below:


Carl's Skeleton v2
The dispenser arm worked well but now I had another problem.  The arm would't fit or look right with Carl sitting down in a chair.  So I then had to build a standing, rigid skeleton for Carl.

In this photo I'm testing the angle of the dispenser arm.  It has to be angled down far enough for the Play-Doh cans to fall out, but also forward enough to look like he's handing the Play-Doh to a child.

Hey Carl Can Stand!
A large pair of shoes and leaning Carl's body slightly forward of his center of gravity helps him to stand.  Notice in this photo I haven't attached the dispenser arm to the final skeleton.

Carl and me in full safari gear ready for Halloween.

Check out the video below for a demo of Carl giving out Play-Doh.  Most kids loved him.  Some were terrified of him.  Dozens of parents forced their children to have their picture taken with him.  There were some pretty funny moments this year.

Saturday, October 30, 2010

Introducing Carl

Carl is based on a WowWee Alive robotic chimp head.  I won't go much into the history of the head itself since there's a lot of info on the Internet.

WoWee Alive Robotic Chimp
My wife got Carl's head for me at a garage sale.  She says the minute she saw it she knew I'd love it and boy was she right.  I knew exactly what I was going to do with it.  You see, by itself, it is literally just a head sitting on the upper half of the shoulders.  It was obvious to me that the head needed a body!

I proceeded to do some rudimentary carpentry and build a simple "doll" body I could place Carl's head on.

1st generation body for Carl
As you can see from this photo, the body is extremely simple.  It just needs to be able to support the head mounted on the shoulders and sit in a chair.  I wanted Carl to stand about as tall as a 6-year-old child so I went the the local Goodwill Store and purchased a set of clothes for a few dollars.  I got my measurements for the torso, arms and legs from the clothes.

Carl's hands 1st gen.
The most difficult thing to build where the hands.  I wanted something I could form into the shapes of hands and bend/mold as needed.  I found the solution in cutting up an old license plate I happened to have sitting around in the garage.  I'm sure any old sheet metal would work fine.
Use foam padding for realism.

Bolted to the chair and zip tied to the bucket.