As promised in the last post, here’s a look under the hood of how the Sparrowscope works. The motors are controlled by a smart phone, but of course smart phones don’t have motor outputs. So how will this work?
The smart phone will communicate with some intermediary electronics, which in turn will drive the motor. And of course, the standard connector across all phones is… the headphone jack! I didn’t want to limit devices to only an Apple connector (and then it’s a pick between Lightning and the older 30-pin connector), or USB for Android devices. Bluetooth has too much of a delay and would make the Sparrowscope more expensive and less easy to experiment with. So that’s why the Sparrowscope is going to use sounds over a headphone cord to communicate. By playing different tones, the smart phone will tell the circuitry how much to pan and tilt.
Here’s a video I took when I was testing the frequency measuring code for the first time:
I’ll go into more detail on the communication protocol in the coming months, so that it’s completely open as to what tones will control the Sparrowscope. It will be possible for tinkerers to easily make the Sparrowscope do what they want it to—anyone could make and share their own app. Maybe you’d like a more complex control loop, using the compass in your phone to aim the camera by heading angle? A panorama-making app? You could even send up something other than a smart phone. Maybe lift an aerial Raspberry Pi? I’m exited to see all the creative things people do with their Sparrowscopes!
You might enjoy this little clip I filmed from the skies, one of the first times I attached an iPod Touch to a kite line. I used a 4th generation iPod, hence the poor video quality—the new ones are much better.
Anthony and Mai, my former lab mates from my grad school days, took some pictures of the Sparrowscope while it was filming them. The movie climax is definitely when Anthony lies down on the grass and waves.
Alright. I’ll concede that this isn’t the most exciting video on the Internet. My next video will be more technical—a test of some circuitry and code that demonstrates how the Sparrowscope is controlled by a smart phone (Edit: that’s online now, you can view it here).
All kites are not created equal. It’s important to me that only great kites are used to lift the Sparrowscope; cheaply-made kites are an avoidable risk to your equipment. Even if a kite flies, it may not move around too much in the sky for stable camera positioning, and a kite that does unexpected acrobatics can be quite stressful.
For that reason, I plan on including a kite with the Sparrowscope. I’ve ordered over a dozen kites from reputable manufacturers, and I’ve taken advantage of nice fall weather (and now, mild winter weather) to test them out. I’m making note of:
Wind range in which the kite can lift a Sparrowscope
Stability (keeping put, not diving suddenly, and not over-flying)
This testing has proven quite valuable already—here’s what a spar looks like when it breaks in mid-flight! There fortunately wasn’t a Sparrowscope on the line when this happened. This is the kind of problem I’d like to avoid for my customers, which is why I’m testing in a variety of conditions.
I’m really putting these kites through the paces, and I’ll continue to do so while working on the prototype before I settle on the model to include. I’ll end this update with some pictures I’ve taken while testing kites.
I’ve created a business, set up a tax account, opened accounts with various suppliers, got a logo… I even made this website that you’re reading right now. It’s all important, but not very glamorous. I thought I’d mention it anyway.
I’ve built some prototypes, and made improvements based on my results. I’m trying to accomplish a few goals here:
Reduce setup complexity
Make the rig more stable
Measurements of one of the prototype configuration’s twisting motion.
This means I’m not only trying out different features, but I also am making slight variations to the design while measuring performance. I’m definitely geeking out with this project—for example, here’s a plot showing how the rig twists in all three axes. I want to reduce the magnitude and the frequencies of these vibrations, so that pictures and video from the Sparrowscope will be as stable as possible.
I’ve recently started on a major change to the way the Sparrowscope works, and if my experiments continue to be promising, I’ll have something exciting to show you all soon.