DIY optical lenses

For my AF Assist tool, I decided to make my own optical lenses to focus the light from the IR LED. I experimented with a few lenses I had kicking around (from other flash systems that I took apart) and looked online to see what I could purchase. The lenses I had kicking around did the trick in giving me a direction to follow, but were not prctical for several reasons. Sourcing is a big issue (these are custom lenses) and second they don’t quite fit my application constraints; too big, or need to be too far away from the light source.

After a brief search online (ebay, aliexpress, etc) I decided that I didn’t want to wait a month for some lens that was chosen just on a photo and scant technical info.  It’s too much trial an error for my taste. I’ve always been intimidated by optics. It felt like this black art/science that I knew next to nothing about. Having done some reading, I now feel a little more comfortable attempting to make my own optics.
Besides, learning something new is always great.

I’m approaching this from a couple different angles. 3d printing of a master (and then resin cast using optically clear resin) as well as cnc machining a mold and try to form some acrylic plastic sheet into the shape i want. I don’t quite know which will give better results which is why I’ll take both paths.

 

Links:
DIY Plastic lenses
– 3D Printing and CNCing Weird Freeform Lenses
– Bike pump Vacuum pump

 

 

 

A quick CAD sketch for a mold, and then a 3d print resulted in a

Lens01Lens02

Crashplan memory problems

I updated to the latest version of UnRaid (v6.2.1) and Crashplan that runs ina docker container started misbehaving.

At first it kept cycling through “Syncronizing block information” and would not actually do a backup. It was stuck in a loop doing the sync operation.

I then changed the frequency of when the backup runs, by telling crashplan to run the backup between a specified time and days for all the backup sets.
That stopped the repeated sync operation, but now while doing backups, the Crashplan application (and engine) would crash and restart every minute.

I tried changing the -Xmx parameter in the run.conf file, but the restarting behaviour persisted.

I can monitor the docker container memory usage using the “cadvison” container, and I can see that as memory usage gets close to 2 GB, the system would restart that container. I bumped the -Xmx parameter all the way up to 4096MB, but it seems like it’s stuck at 2gb…

The next way I came across to increase the allowed memory usage is entering the CrashPlan console from within the app, ans issue the command “java mx 4096, restart”.  (SEE LINK)

This successfully increased the allowed memory usage of CrashPlan to 4GB. Looking in the “cadvisor” app, I can see that crashplan now uses 3.5GB of ram, and everything is stable.

What tool to use for CNC mill or router?

Excellent three part series of articles talking about the right tools required along with many side articles providing more details.

How Can I Figure Out What Tool to Use On My CNC Mill Or Router? (Part 1 – Holes)

How Can I Figure Out What Tool to Use On My CNC Mill Or Router? (Part 2: 2D Profiling)

How Can I Figure Out What Tool to Use on My CNC Mill Or Router? (Part 3: Pocketing)

 

 

 

Strength degradation in webbing and cord with introduction of knot

I’ve always used webbing for setting up top rope anchors, but recently I’ve investigated using cord instead of webbing. For one thing, knots are easier to undo in cord then in webbing after being loaded. But is there any difference in strength between knots in cord and knots in webbing?

Interesting to see that a knot (Bowline of figure 8) will introduce a weakening to 73% of cord tensile strength.

Maybe more interesting is that in webbing, a water (overhand) knot degrades the strength much more then a figure 8 knot. Water (overhand) Knot gives a 57% of webbing tensile strength, while a figure 8 gives similar to a cord figure 8, at 71% of webbing tensile strength.

http://www.bethandevans.com/load.htm

 

Find and change quality setting on image files

The webserver I was working on was running out of space only to find people had been uploading anywhere from 3Mb to 9MB jpeg images. Nobody needs that kind of image size and quality on the wordpress site.

Put together a script to for find and re-encode jpeg images over a certain size, to a lower quality setting.

find . -type f -size +1000k -name “*.jpg” -exec mogrify -quality 50 {} \;

CrashPlan stuck at analyzing

I had this problem before where CrashPlan (the backup service) software will seem to be stuck “analyzing” data over and over without actually backing it up.

The last time that happened I had found no way around it except to re-start the entire backup. And since it takes months to transfer 1.8TB of data, it wasn’t a decision I tool lightly. I had searched all over the web and tried everything I could find, but to no avail.

This time I did some more digging again, and found a solution that worked.

CrashPlan for me runs as a docker container under UnRAID and UnRAID is a virtual machine in my ESXi homelab. I had 4GB allocated to UnRAID to do what it needed to do. The memory usage (at least as reported by unRaid) was about 60-80% so I dind’t htink I was running out of memory, but seeing as no other solution was working this time either I made 2 changes.

  • Increase the amount of ram that CrashPlan can use (as per this article)
  • Gave UnRAID 4GB more ram for a total of 8GB.

Between those 2 tweaks, the next time the CrashPlan app started, it wet straight to actually transferring files instead of “analyzing” them.

ESXi and PCI passthrough

So the troubles seemed to be over with the ESXi server crashing when I was starting VMs that used PCI devices which had been passed through, but I was wrong.
The Win10 VM that had the GPU passed through is now once again either locking up the computer (ESXi locks up) or I get a PSOD (purple screen of death).

I read about others reporting similar issues and I updated the ESXi install to the latest build of version 6.0.0, but the problem persisted.
For reference, this is a listing of all the ESXi versions and updates and links to how to apply them (source).
One thing I just tried is disabling Interrupt Remapping (source) to see if it had any effect. It had no effect.
Removed and added the GPU device from the list of passed through devices.

VP multi-rotor: development testing

I figured I should put together a list of what the development tests I want to do before setting out to actually build a prototype of a VP quad. The temptation is high to just build something, but I know I will learn a lot more by doing some testing ahead of time in a controlled environment.

Would like to build 2 test stands. One based on Trex450 heli parts and another based on Trex500 heli parts. Both are available in belt drive or torque tube, both are available from HobbyKing and hence are quite inexpensive.
The rigs need to be modular enough to test both belt and torque tube designs.

What I would like to test:

– How much power can be handeled by either torque tube and belt drive

– Failure mechanism at high power. (what fails first?)

– How much does the boom flex (carbon vs aluminum) as this may impact the effectiveness of the torque tube?

– Ability to test out different blades (length, profiles) at different angles of attack, and record thrust vs RPM vs angle of attack.

 

What I will need:

– some sort of I/O card for data acquisition so I can record in real time things like RPM, blade angle, voltage, current, thrust, displacement/bending of booms,… (add more)
Preferably a USB solution so I can use a laptop to do the data recording on Labview?

– a test rig that can accommodate the data acquisition parameters. Also needs to be  inside a lexan or mesh enclosure so failure testing doesn’t hurt me.

 

Rig Design:

I will start with a heli body, since i will be using all the gearing inside the heli body and stick a motor in side
Figure out the gearing first.

Resurrecting my old Amiga 4000 (currently not working)

Got my old Amiga 4000 out of storage at my parent’s place and decided to relive the glory days.
I still remember the great times I had with all the amigas I had owned. Starting with an Amoga 1000, then an Amiga 500, then an Amiga 2000 and finally an Amiga 4000. A few years after getting the A4000, I even remember dropping another $1000 on a Cyberstorm MKII 68060/50 Mhz accelerator card.
It must have been nearly 20 years since I powered up this machine.

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