Blog Postings

projects:fluke8840a:start I've managed to acquire a very nice Fluke 8840A multimeter from eBay. This is a 5½ digit desktop multimeter with RMS AC and GPIB options installed. It seems to be fully functional.. except for the VFD display which is showing some signs of age and where the brightness is a bit uneven and somewhat dim.

I think another display replacement project might be in order! More info on the Project Page.

Based on lessons learned from the Fluke 8050A project, I'll do things a bit differently this time around. Also, the nature of the Fluke 8840A meter is a bit different, and I'll necessarily need to adapt to that. I think this time around, I'll use an STM32F407 based board with more I/O pins. The board is a bit larger, but I don't think that space is an issue. The cost is a bit higher, probably $15 vs. $5 for the STM32F103 “Maple Mini” cloned I used before, but there are lots more I/O pins available, and more importantly, more 5 volt tolerant pins. Also, additional peripherals will be available such as UART, SPI and I2C (and the pins to use these.)

This opens up some other options, such as including a Wi-Fi or other communications options, data logging capabilities (the STM32F407 boards have a microSD card slot available, not to mention a bunch more RAM. Maybe an audio annunciator? Who knows?

2017/09/09 02:18 · Louis Mamakos

Got to see James Web Space Telescope in the vib test facility at NASA Goddard today. Took a few photos..

These first photos are with the structure mounted on the horizontal table that provides movement parallel to the ground in one axis. To test the other axis, the test article is rotated 90 degrees. Behind it is another test station that can vibrate in the Z (up/down) axis. Sadly, I neglected to get a photo of the other testing apparatus. It's all very large, but the mechanical tolerances are still very exacting.

You can see the spacecraft components inside the “tent”, which is essentially a portable clean room. It will move within the envelope of the tent when the testing occurs. If you look carefully, you can see one of the folded up mirror assemblies.

After vibration testing, there is an acoustic testing chamber used to simulate the low frequency acoustic energy produced by the launch vehicle.

These photos attempt to capture the scale of this. Note the doorway inside the chamber for scale. Those large holes in the wall are “horns” or really large speakers. You can also see a hint of two outside doors, but I couldn't get far enough back to get a good shot of them.

2016/12/21 03:47 · Louis Mamakos

I was inspired to do something stupid, so I purchased an Autel Robotics X-Star Premium “drone” quadcopter. It's pretty fancy, with being able to shoot 4K 30fps video from a stabilized 3-axis gimbal (so when the aircraft changes orientation in pitch, roll or yaw, the camera stays where you left it).

I did get the Orange color (rather than white). It seemed like it would be easier to see against the sky while flying, though that's not necessarily a good thing since we've many well-armed people living nearby. As it has a flight time of a bit over 20 minutes per battery, I did order an extra battery. I can see that maybe having one or two more might come in handy.

You fly the thing with a nifty remote control. Really, you direct it rather than fly it. The aircraft as a pretty sophisticated on-board “autopilot” with a GPS receiver, solid-state accelerometers, gyroscopes and magnetic compass. Once flying, when you release all the inputs, it will just hover there in the air, fixed in position. Even with a pretty good wind blowing, it will maintain its position. You can turn all that cleverness off if you like, but I'm not anxious to try out the crashing part of the experience. It has one-button take-off and landing (back to the location it took off from!)

The video from this thing is really quite astonishing. It will take 1080P video at up to 120 frames per second. For higher resolution, you can take 2.7K video at 60 frames per second and 4K video at 30 frames per second. My old iMac can't even render 4K video smoothly without stuttering – that's 4 times the resolution of your 1080P HDTV.

You can also take 12 megapixel still frame images, too. Here's one as an example (and click through the thumbnail to see the full resolution)

This was taken on “full-auto” on a cloudy day; probably the white balance is off a bit. You can also shoot “raw” uncompressed images and do processing on them later. Pretty slick.

Not only can you record images and videos, but while flying, there is a “First Person Video” downlink from the aircraft that you can watch in the application you run on your phone or tablet that's connected to the remote control. This application is a “dashboard” where you can see real time video from the drone, and other data overlayed including altitude, speed, lat/long position, distance from the “home” point that you launched from, battery status, remaining flying time and other stuff.

The application also plots the track of the drone on a map. You can use this map to set waypoints and an autopilot function on the aircraft to fly a course through the waypoints, orbit a waypoint, or even to have it follow you (really, the remote control) if you're moving around on the ground.

Big fun!

I've put the raw videos from the first few flights on YouTube in a playlist here. There's also another video I made where I edited together parts of two videos to capture the entire first flight. Sadly, the old iMove '09 software and quicktime that I have on my iMac takes the wonderful 4K video and produces only a 720p lower-resolution version. But it has a musical sound track!

More drone stupidity to follow, I'm sure.

2016/10/01 15:26 · Louis Mamakos

Just doing some tuning to the dokuwiki configuration used for this site. While this software is primarily intended for use as a traditional wiki platform, there are some plugins that can add blog capability. While it seems like everything I'd want for my simple needs is in there, I just need to get the configuration knobs tweaked to behave just so.

Some of this is my not being quite sure how I want the start page to work, with presentation of project-based wiki content as well as some blogging content.

2016/09/21 15:15 · Louis Mamakos