Hey everyone, thought I'd put up a quick into.  My name of course is Dave and I grew up in Northern New Jersey, USA.  Next to my name in the dictionary it says, "Breaking Warranties Since 1973". Pretty much starting at the age of 4 (according to my parents) I began taking apart every single toy I owned to see how it worked and somehow managed to put them all back together.

I was lucky growing up because my father worked in a machine shop.  They used to design assembly line robotics. I can remember him bringing home boxes of parts all the time for me to tinker with.  I was always building something for fun, or the science fair or just to creep out my friends (mostly around Halloween).

I studied drafting extensively in High School but when College came about I drifted from Architecture to Mechanical Engineering to Electronic Engineering and eventually settled on Electronic Engineering and Computer Science.  My claim to fame is inventing the first digital (non-chemical) photo booth for a company I co-founded.  Eventually I got burned out on electronics and went into web design and eventually settled back into software engineering which took me on a journey from small company to small company eventually settling in at IBM.  After my tenure at IBM, I went back to working at a small company in North NJ where I am today doing both Electronics Engineering and Software Engineering.

My wife and I are also very big Halloween people.  We've been running a successful 1/2 acre haunt on our property every year since 2009 and have build a bunch of animated props and scenes.

My life long dream hobby has been robotics, artificial intelligence and home automation.  Our home is quite automated and a lot of it was developed custom.  Our home is also voice activated and that is where the AI comes in.  Finally, with the birth of affordable 3D printers I am jumping into my Robotics Hobby feet first and working on a full size humanoid robot which has been a life long dream.  That is what brought me here to Stan Winston School.  Hoping to learn a lot!!!

My original plan was to use 3 servos for the left/right and front/back tilt.  I had designed the ball and socket to also have ball and socket linear screws.  The top half of the linear screws are clipped in place.

The problem I ran into with this linear screw drive was binding due to the 3D printing.  I could not get the spiral thread to run smoothly no matter the design or material.

After some tinkering I felt the Universal Joint design that Jim showed us would be a much better design.  So back to Fusion 360 to design a U-Joint.  You can see below I designed a rough prototype that fit into my neck tube and designed a new plate for under the gearbox.  This proved to be a much more smooth design.  It had a lot of slop in the joints due to it being a quickly designed prototype.  I've since tweaked it to close up some of the gaps and bring the tolerances in a little tighter.  That is on the printer as we speak.

Sweet!

So after I 3D printed the U-Joint I realized I was out of nylon so I never was able to print the final version.  The Silver nGEN Filament worked well but wouldn't hold up to real weight.  So I shifted gears and purchased a few of the parts from Jim's list just so I could show that I know how to measure, drill and tap.

So here is the cheap McMaster Carr U-Joint along with the proper 1/4" stainless shaft, Eyelets and collars.  I did break a tap in the stainless so I had to buy another.  Got to take it slow with stainless.


Since I had some servos and didn't want to spend on servos I would never use, I used my Nylon servo holder. Again, just proof of Drilling, Tapping (oh and some 3D printing).

So, to test my servos I made my own servo tester.  Took a simple potentiometer and threw it on a bread board.



I then took an Adafruit PWM Servo Shield.  This shield has it's own power source and can run up to 16 servos.  You can also change the address of the board so that you can stack 6 or them giving you 6x16 servos total.  I mounted it on top of one of my arduinos that is in a 3D printed case.  I connected my potentiometer to 5 volts and ground.  The other end of the pot connected to an analog pin.  When configured the pot gives me a reading of 0 (all the way counter clockwise) or 1023 (all the way clockwise).  I then also connected my servos of servo port 0, 1, 2.

I ended up using servo extensions so I could have the arduino a little farther away.

The simple test program for the servo tester simply mapped my pot reading of 0-1023 to 0-180 degrees.  It was able to control the servo easily using the adafruit library for their servo shield.

After that, I wrote an automated test that would basically do a nod (both servos up and down), then would do a head lean, one servo down at a time.  Then my third test would be left and right rotation which would be testing my pre-existing neck gearbox that I haven't moved to the new neck yet.

Cool!

*** So this is post homework turn-in. Just wanted to share some continued progress after the fact.  ***

I took my gearbox off my other nylon assembly and mounted it atop my neck.  This gearbox is my (Yaw) rotation around the Z-Axis.

One thing I did not account for when I redesigned my neck plate was to account for the eyelet height on the rod ends.  When the gearbox rotates the front herringbone gear just ever so slightly clips the rod end.  So I am going to need to go back into Fusion 360 and add about 3mm to the top of the neck plate.  This should raise the gearbox just enough without changing anything that would affect the geometry.

... and it's fixed.  Printed the new part this morning.  Gearbox clears without issues by a couple millimeters. Glad it was an easy fix and also easy to replace this one part.