For the human movement with a motor project I’ve picked blinking, which seems a very simple movement of the eyelids in everyday life, however, it turned out to be a nightmare to build the blinking mechanism.
I went through a bunch of ideas when it came to coming up with a mechanism to make the eyes blink, and the most appropriate seemed the mechanism that is used by the puppeteers. So I then researched how that mechanism works and tried recreating the mechanism using what I had in the lab : a bunch of popsicle sticks, cardboard, rubber bands, paper, some wires and a bunch of hot glue.
I mean, I was expecting this assignment to be less bout writing the code for the arduino and the motor, and more about constructing, but this one turned into a serious mechanical engineering assignment for me.
I made the eyes simply by wrapping tennis balls with paper, but then I needed the eye lids. I thought of manny different things, even about making a clay mold, but clay takes too long to dry. Somehow I come up with using hot glue to make the eye lids, and since that point hot glue became my best friend for the project. I wrapped the eyes with another layer of paper and drew a grid with hot glue on top of it, so that when the glow dries, it holds the spherical shape of the eye. Then, I cut the excessive paper off the sides, and those were my eyelids.
After I had my eyes and my eyelids, there came the time for making the mechanism. Out of all the material I went through to figure out how the puppet’s eyes blink, I found this video the most useful one.
So I decided to replicate it using cardboard, popsicles and rubber band. The middle part, or the lever, was not stable enough since it was made of cardboard, so I had to come up with some construction that holds it in place and does not let it fall on the side.
To construct the lever, I drilled four holes in the popsicle stick, and then also glued some additional support to each side of the stick, so that it does not split when the pressure is applied. Apparently popsicle sticks are very fragile due to being very thin, so they split and break very easily.
This is the close-up of the lever with the wire and rubber band put through it.
And this is the top view of the construction, it gives a greater understanding of what is attached where and what helps to support the construction.
Having built that, after gluing some popsicle sticks to the back of the eyelids so that they close whenever the lever is pulled down, it was time to understand how to attach the metal wire I am using to pull with to the motor. Luckily for me, I found a motor that is attached to a gear set and a wheel, which slows the rotation speed of the motor by a lot, so I just had to connect the spinning motion of the wheel to pulling the lever.
I glued a stick to the wheel and then attached a piece of rope to it. But it didn’t work that well because the rope would wind around the stick and cause the whole mechanism to shut down.
So know I knew I needed something that is not stretchy or soft like a piece of rope, so I’ve glued a bunch of popsicle sticks together to see how they would work, as if I drill a hole in a popsicle stick, there is nothing to get winded on the motor.
And this is how I attached it to the lever
But now there was another problem that never happened when I was using rope: after rotating for 90 degrees, the motor would not do the rest of the circle, because the eyelids are pushed against the box and there is no space to go lower than that. And since the stick cannot stretch, it does not forgive. With the help of Aaron, I understood that the problem is the position I chose to attach the stick to the lever. I attached the stick to the lever when the motor wheel was at its highest point, and the eyes were in “resting” position, and the wheel was too big to go all the way down without causing the eyelids to push against the box. The fix was to attach the stick to the lever when the wheel is at its lowest point (which it could not reach with the previous setup) and then to the eyes that are closed (the lever pulled).
Now the wheel could make a full circle! Even though with a little help when it had to pull the eyelids, because the motor was not strong enough, but besides this one point it was getting stuck at due to the lack of power, it did the rest of the circle on its own!
Here is how they blink.