Project Logs

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• Talking to the Big Easy Driver (BED)

  John Leeman • 05/04/2017 at 04:32 • 0 comments

  The next step was getting the turntable rotating using the Big Easy Driver (BED) and the Raspberry Pi. Luckily, the BED is very simple to control, with three pins setting the step size (full, half, quarter, eighth, or sixteenth), one pin setting the direction, and another instructing the motor to take a step. I whipped up a little driver in Python and was ready to test it out.

  I hooked up the BED to the Pi and a power supply for the motor. Running the code produced no rotation - after playing around and looking at the outputs, I determined that I needed a longer pulse to the step pin that actually tells the driver to move the motor. The documentation states that 1µs high and 1 µs low is adequate, but I found that values around 1 ms worked much better. There was also some tuning is the timing to get the motor to move smoothly and reliably. In fact, I wrote a quick test script that would move the motor a random number of degrees in the range 0-360, then back again. It did this a few thousand times to simulate many days of steering based on changes in the wind. The motor did return very close to its initial zero position!

  My initial idea on making sure the turntable did not turn more than 360 degrees and wrap up the camera USB cable was using two magnets and some hall sensors. While that should still work, I think I like the idea of putting an inexpensive magnetometer on the table (maybe the MAG3110). Actually knowing the direction that the camera is pointing will prevent any weird edge cases with power cycling or winds that hover right around the point at which the table would need to switch direction. For the small amount of expense added, this is a huge boost to reliability.

  So the motor is turning, now we need to design and add the wind-vane, as well as start taking photos. I’ve been working on the code for the wind vane, environmental sensors, and interface in the repo, but it is currently all untested.

• Enclosure Assembly Complete!

  John Leeman • 04/29/2017 at 22:31 • 0 comments

  We have an enclosure! This weekend I was able to get the 8”x8” electrical enclosure drilled for the stepper motor and dome covering the motor. Here’s a quick synopsis of what I encountered.

  Mounting the motor took slightly longer than expected simply because I didn’t have any M3 standoffs on hand. I measured the length of standoff needed to keep enough of the motor shaft above the lid to affix the turntable on and it was just over 0.5”. Since a 0.5” standoff can be obtained, that should be used for the final kitting. I turned some custom standoffs since I didn’t have any in the shop though. Using some 0.25” 6061 Aluminum rod, I drilled it out to a free fit for the M3 screw and turned to length. It was a good exercise in getting my little shop lathe broken in and prevented me from waiting on the parts for a prototype. I used some long M3 screws and cut them down to fit. Again - all simplified in the final BOM.

  Drilling the holes for the dome was relatively straightforward. Using a set of calipers, I adjusted the position of the dome iteratively until I had an equal reading to all four sides of the lid. One thing I had to make sure of was that the mounting holes would not interfere with the seal of the lid. As long as the holes are not right at the edge of the lid, everything clears, so I simply had to make sure that the dome was well oriented when aligning and marking. I marked the holes and drilled to snugly fit a #6 screw.

  The turntable for mounting the camera is a ceiling electrical box cover plate - it was the perfect size and less than $3. I found the center with a pair of calipers and laid the motor mounting hub from SparkFun over the center. Again, I marked the holes and clear drilled for the 4-40 screws that the hub is pre-threaded for. I’m unsure why on a motor with M3 mounts, SparkFun chose to use a #4 screw for the hub, but it works. I then mounted the hub to the motor and the plate to the hub (in that order, so that the set screw was accessible.) The turntable was just scraping the top of the lid, so I added a few washers to space it out further, confirming that 0.5” length standoffs are the way to go.

  Finally, I mounted the camera to the turntable using double stick tape. I looked at how to drill and mount the camera, but ultimately found it to be unnecessary. The tape should also help with an vibration during rotation. I drilled a set of six small holes in the lid near the edge of the turntable and filed them out to be a square that allowed the camera’s USB cable to pass through.

  That’s it for this update, stay tuned as we get the motor turning and start capturing pictures.

• Meet the Project!

  John Leeman • 04/14/2017 at 13:16 • 0 comments

  As the first project log, I thought it would be a good idea to really outline the goals of this project, throw out some questions, and generally crystallize the concept behind the wind pointing time-lapse camera.

  The Problem:

  I want to create a tool to allow students or interested meteorology enthusiasts to see the atmosphere flow and understand what is really happening then a front or storm passes by. The atmosphere flows like a fluid with instabilities, density currents, and many other phenomena that are fascinating but difficult to follow due to their relatively slow movement. Static cameras are great, but don't always follow the most interesting weather. 360 cameras are expensive, produce a lot of data, and require the user to search for the most interesting views.

  What the project does:

  This project takes time-lapse photos of the atmosphere and combines them with meteorological data on a webpage that can be easily explored. The camera is continuously pointed in the direction the wind is blowing, so nature is steering the lens to point at the most interesting phenomena in the area. The photos and data can be explored at all levels from quick view to in-depth data analysis and discussion.

  How it’s going to change the world:

  Understanding the Earth is a monumental task and something that is not ingrained in many people. With increasing urbanization and modernization, the intuition and connection to natural processes gained through experience is all but gone. This project helps speed up nature so we can experience how dynamic our atmosphere is. In addition, it is designed to be inexpensive so that it is accessible to schools, students, and hobbyists. By using 3D printing, open source hardware and software, and modern design tools, the project can easily tie into many portions of the STEM curriculum. Students can build a real and useful scientific instrument and learn from the process and data. The time-lapse videos can also be shared as a community resource.

  License:

  The project is under the MIT license – in non-lawyer terms that means you are free to do whatever you wish with any of the project content, but there is no legal recourse against me no matter what happens. I really like such a permissive license because, let’s face it, there are a lot of ideas out there and we all gain by sharing.

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