Ever since I saw the Little Bot project from Matt Chilbert at BirdBrain Technologies, I’ve day dreamed about using his ideas to make a plushy rabbit toy.
But, have you ever tried to mount a motor into toy stuffing? Making a squishy toy that has motors inside isn’t easy. Below is the story of how I tried – and am still trying. I didn’t have directions to follow. I just knew that I wanted a plushy bunny that would “look around” like a real rabbit.
For each idea in this process, I tried lots of other ideas before I moved on to the next idea. Also, sometimes I got on an airplane in between ideas because I travel a lot for work. (Those photos are below, also.)
My goal is to create a simple robot plushy that mimics life-like behavior. If you have shareable resources on this topic, please email them to me firstname.lastname@example.org. I’d love to see them (and share them in the next blog post.)
This 14 second video has music.
Key Ideas I’ll Try Next Time
- Insert electronics from the tail of the bunny, not the head.
- Try attaching the head separately and last. This might make for a more emotionally appealing face because you can get the details right before attaching it.
- Use fabric that doesn’t shred easily. Felt or wool might be a better option than what you see in my photos. (I used micro felt because it was extra soft. I thought it would move nicely with the micro servos, but it ended up just fraying easily at the edges.)
- Try micro servos with plastic gears instead of metal gears to save a few dollars.
Materials You’ll See Below
Felt, embroidery floss, needle (any will do)
Eva Foam 10mm thick (You can get Eva Foam at JoAnn fabrics)
Cutting knife/cutting mat
Here we go
First, I started with a simple cardboard version. (Hey, it looked like a rabbit to me.) I programmed it in MicroBlocks.
Well, that was easy enough. I put a picture of the MicroBlocks bunny Rosa on the front and called it a day. That was all I had time for before I went to FETC in Miami, Florida for work.
Once I returned from FETC, I had to go to the BETT show in London right away. So, my bunny project waited a few more days.
Once I got back from BETT, I had a new idea to try. I chopped up a memory foam pillow, and made a servo shelf with 2 pieces of 10 mm Eva Foam. The Eva Foam securely held my servos, but the servos weren’t strong enough to move the 2mm black foam (AKA: future bunny face) the way I liked. So, I ordered micro servos with metal gears, thinking they’d be stronger. (This may not have been necessary because the most recent design I’ve used is fairly small and light weight.)
Also, memory foam is difficult to cut without special tools. Of the tools I had available, a bread knife was the best solution.
After I tried that idea, I had to pack my suitcases again to go to TCEA in Austin, Texas. TCEA was a strangely green trip.
Okay, Now We’re Getting Somewhere
Once I got home from TCEA, I spent a lot of time preparing for the class John Maloney and I were teaching at Infosys Winter Pathfinders. We had video meetings most mornings.
After one of our morning meetings, I started working on the code for my future rabbit. I knew I wanted to use the radio feature of the micro:bit to wirelessly send messages from one micro:bit to another micro:bit, in order to control the servos. Below is the program I wrote.
During the class we taught, I managed to find a few minutes to try making another type of bunny head.
Once I got back from Infosys Winter Pathfinders with John, I was ready to dive into my project because I had 8 full days before traveling again.
First, I decided that I had a good concept for stabilizing the servos with Eva Foam from the memory foam rabbit.
This is a soft and durable way to stabilize the servo motors, so I decided to keep it.
Next, I decided it was time to get a real pattern. I knew I wanted a plushy rabbit, so I searched free rabbit patterns. I chose the pattern below because I thought the servos would fit well in the neck. (I noticed that the distance between the base of the rabbit and it’s neck was similar to the height of my servos stacked on top of each other.) So, I traced the pattern and cut out the shapes from my fabric.
Even though the directions showed me how to stitch these pieces together, I still had to figure out how I was going to insert my motors. I also needed to figure out how I would attach the motors to the rabbit itself.
Next time I will NOT insert the motor in the front (as I tried here). Next time I will stitch up the front of the rabbit and leave the back open. There are several seams on the front of the rabbit, and trying to stitch them together while holding the motors in place was very tricky. This trickiness combined with the fraying fabric makes the front of my first-draft rabbit pretty raggedy.
Here’s what happened. (The black thing sticking out of the side when the head turns is a piece of 2mm foam. You’ll see more about that piece below.)
Fourth/ Some Things I Did Next
See how well it works?
So this is what went inside of the rabbit’s body.
Yes, it’s a bit floppy outside of the rabbit, but once it goes inside, it seems to work okay. There is definitely room for improvement in this form.
Programming My Rabbit
Once I sealed my servo motors inside of the rabbit, I didn’t know how exactly they would move. Using MicroBlocks was a good choice for me because I could quickly make changes to my program. I needed to find out how far my rabbit’s head could move without looking crazy, or worse, falling apart. By using MicroBlocks, I could test in real-time (no waiting for something to download) the range of my servos inside of the rabbit.
Pressing A on the micro:bit causes the rabbit to rest. Pressing B on the micro:bit creates a random rabbit movement. My next step is to make these radio controlled features so that I can remove the wires (as you saw in my example code above.)
This 14 second video has sound.
Need More Resources
If you have shareable resources on the topic of simple squishy robots, would you please email them to me, Katie@katiedays.com? I’d like to learn from them and include them in my next blog post.