HackHD 1080p Video Camera
The week prior to the scheduled launch of EDGE2, Sparkfun announced that they were carrying an exciting new HD video camera - the HackHD (Sparkfun Product Page) (Manufacturer Site). This board-level camera promised 1080p 30fps video, and was too good to not fly. As far as we know, we're the first group to strap this particular camera to a high-altitude balloon, and we're thrilled with the results. A highlights video is below, but really, you want to read the technical details that we discovered before you get to that, right?
First off, the included documentation that we got was a little bit lacking in detail, some of it critical to designing a high-altitude payload. Specifically, there was no information at all about how much current this module consumed during recording, so the very first thing we did was hook it up to a bench-top supply to characterize its power requirements. We used labview to sample the current consumption of the unit at 3.7V and 4.0V. The labview routine that we used was a really quick job to get us the info that we needed, so it's not pretty - the vertical axis has units of Amps (so 0.6 = 600mA), and the sample rate was about 0.75Hz. Also worth noting is that halfway through each run, we disconnected the LED from the terminals to see if that made a difference (it didn't). The graphs below are the result:
Based on those results, we averaged a little bit high and decided to assume a 650mA current draw during record. We picked 4 hours as a target battery life, resulting in the need for a 2600mAh single-cell lithium polymer battery, and then we found this battery from Sparkfun – 6000mAh. Since we had room and the weight capacity, we decided that bigger is always better when it comes to batteries, so we got that battery and topped off the charge.
It’s worth noting that prior to the flight we also checked to see if a Class 4 uSD card would be fast enough to handle the video that this camera put out (we didn’t expect it to be). It’s not. Really, really not. The resulting video was halting and skipped frames frequently to make up for the card (though we've seen on Sparkfun discussion on the unit that others have had success with slower cards). Once we saw that, we dropped in a 16gig Class 10 card, which worked great.
So, here’s the video of the launch, burst, and landing, all shot with the HackHD. If your bandwidth can support it, watch this in 1080p: at launch you can see the airborne chase team in their Cessna 172 (the folks at the other end of the radio link during the countdown), and at burst you can see the latex and talc cloud in a few frames. Nothing has been changed at all about the playback rate or the audio.
So, how close were we? The HackHD recorded for 2 hours 31 minutes before we turned it off, and consumed 1660 mAh out of our 6000 mAh battery, for an average consumption of 664 mA current draw during record. Also of interest is that the recorded file format is *.mov, and that we used 13.4 GB out of our 16 GB card (roughly 91 MB/min data rate). This unit will definitely be flying on our payloads in the future.