A few weeks ago I was eating a grapefruit when I noticed that several of the seeds inside were sprouting. I pulled them out and put them in a plastic bag to sprout, and started to wonder what I was going to do with 5 grapefruit trees in a tiny apartment in Chicago. According to the internet it’s possible to keep them house-sized by pruning back their leaves and roots. It may also be possible to go one step further and make a tiny grapefruit bonsai tree.
If a bonsai tree grows in Chicago without being documented on the internet, did it ever really grow at all? I decided to make an Arduino controlled timelapse rig to document its transformation from seedling to tree. The idea is to leave the rig going for several years (hopefully), and to keep the tree small enough to fit in the camera’s field of view. The timelapse rig will slowly spin the plant to keep it growing straight and to create an interesting effect in the final movie. After several years I should have a tiny bonsai tree and a pretty cool movie.
Since the grapefruit is a tropical plant and my apartment is dark and Chicago-y most of the year, I added a grow light to the mix as well. Every morning at 7AM the Arduino turns the grow light on, and every night at 7PM it goes off. The light also turns on right before each picture is taken to make sure there’s enough light for a good photo.
In addition to making a cool movie, if I’m going to have a weird plant contraption sitting around my house for several years, I want it to look nice. I tried to keep that in mind while I was designing the base. Originally I intended for it to be a centerpiece for the coffee table, but I ended up mounting it to the wall to save space.
The first step was to design the rig and cut out the pieces. I used some monkey pod and jatoba boards I had laying around. Most of the pieces were cut on the scroll saw, but the turntable was milled out on my Shapeoko. I left the wood unstained, and just rubbed on a few coats of boiled linseed oil to protect it.
Aluminum pegs fit into pre-drilled holes to hold the pieces together, but allow it to come apart if I need to change or add anything later.
I used an old computer fan to make the turntable spin freely. The fan is screwed to the base, and the turntable is attached to the center of the fan. It works surprisingly well.
A stepper motor drives a belt attached to the turntable. Before every picture, it turns the table one step, resulting in a slow spin over the course of several days. I’m using a CanaKit stepper motor and the Arduino Motor Shield.
Here you can see the wiring for the stepper motor and shutter release cable. The shutter release has three wires- focus, shutter, and ground. When focus is attached to ground it tells the camera to focus. When shutter is attached to ground it shoots the photo. A transistor connects each wire to ground, and an output from the arduino triggers the transistor when it needs to take a picture.
After that I mounted everything on the wall using shelf brackets and hung the grow light overhead. Since the grow light requires more power than the Arduino can handle and I didn’t want to burn my house down I used the PowerSwitch Tail to control it. The PowerSwitch Tail is pretty cool. It’s got a normal AC input and output like any extension cord, and 3 screw terminals in the middle than connect to your controller. By connecting the screw terminals to an Arduino pin and setting the pin HIGH or LOW you can switch the power on and off.
It’s only been a few days, but here’s the first second of timelapse footage from the rig. After watching this I realized that the background is distracting, so I’m going to add a backdrop to make the video more watchable. Maybe I’ll start another seed once it’s perfected to make sure the final video captures the entire life of the tree.
I’ll post another video in a few weeks when there’s more to see. All in all I’m pretty happy with how the project turned out. A nice benefit to the grow light is that my office is nice and sunny every day now! It makes working so much nicer, and I’m sure it will be awesome in the winter when everything is dark and dreary.