Tuesday, May 31, 2016

Khan Academy / Pixar Aerial Video by Me

Spent a couple of hours helping make this video, and got two seconds of screen time.  According to the film people, that's a pretty good ratio!

And of course always sweet to do something to help the Khan Academy.

Anyways, quite proud to have done a real bona fide bit of aerial camera work.

I'm embedding the YouTube page, and the Khan page is here.  If you wanna skip the boring parts and see my  two seconds of fame (starting at 0:46), go here.

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Saturday, May 28, 2016

Radio Signal Latency

Transmitter-to-Receiver latency is a much-cited metric when discussing radio systems.

Andy Kunz, a member of the Spektrum development team, wrote a couple of posts going into great detail about how latency is measured and what it means.  Because RCG posts get hard to search, I'm capturing them here for posterity.

I've moderately edited from these posts and a couple in between (quoting people asking questions).

Thanks Andy!

Friday, May 20, 2016

DIY FrSky Receiver

Here's how to make a FrSky compatible receiver with an Arduino and CC2500 radio.

It's also sold as the AirWolf models 1 and 2.  I'm ordering one  to test it out.

Tons of technical information at the link.

blogodex = {"toc" : "AirWolf"};

Saturday, May 14, 2016

A Couple of UMX Radian Videos

Here's a couple of videos of my UMX Radian, a really sweet plane.

Quiet morning flying at the Berkeley Marina

Here it is with a wing mod that makes it into a really slow flyer.

And pretty sweet indoors.

blogodex = {"idx" : ["UMX Radian", "Videos"]};

Saturday, May 7, 2016

Taranis Sound File Formatting

Here's the incantation to generate a sound file playable on Taranis.

ffmpeg -i myfile.mp3 -ar 32000 -ac 1 -acodec pcm_s16le myfile.wav

In human being terms:

- 32,000 bps sampling
- mono
- PCM signed 16-bit little-endian

well for a certain type of human being anyway.

blogodex = {"toc" : "Taranis Audio", "idx" : ["audio", "ffmpeg", "deep, dark magic"]};

Monday, May 2, 2016

An interesting RCG note from Springer at Model Plane Foam. They're a pretty cool outfit... they asked the manufacturer of Dollar Tree foamboard for a foam more suited to model building.
Model Plane Foam is available from modelplanefoam.com. it is the same recipe as the latest Dow fff, white, no film or printing or perforations. Shipping to AZ is high, but it is still typically less than Depron.
Here's the thread with the history and info on it: 
Adams says that the dtf formula is different from the Dow formula which is what we get (less the pigment, of course). A grade MPF has a fine skin with almost a rubbery feel to it that is decently dent resistant. A big part of the difference in both stiffness and durability comes from that skin.When the paper is removed the dtf surface is composed of open cells (no dense skin left at all) which is fragile and dents easily. So the difference in strength/stiffness is a combination of factors. Current A grade MPF is running between .2 and .23" thick, on the low side of the thickness spec.
I'm sure that a big part of the cost difference is shipping (I find it is awfully expensive to ship mostly air!), but process may also be a factor, if I understand correctly, Depron is extruded in flat sheets (probably why it has best flatness) wheras MPF and fff are extruded in a different process that has higher throughput, but sacrifices flatness (sometimes - it varies within a run and is one of the parameters we specifically ask them to control better than they do for fff).
As far as stiffness, density, etc. MPF is targeted at 2lb/cu. ft. From what I have seen of depron, it seems like similar density. Depron is stiffer but more brittle, which I attribute to the formula difference. One customer who made 3d plane kits loved MPF for his planes because a crash that would previously result in a bunch of Depron pieces was a non issue for MPF. He was one of those who milled away foam to make a girder structure in the foam sheet so the increased toughness was important.

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