Rackmount Rollo

Please see the attached postage-printer mount. It's stuck into the 10" side of the 19" rack-o-crap that was on my desk. Made of metal Meccano metal-errector-set stuff, the prototype is surprisingly solid. See one part tested with oxide-red primer. There is room for proper rack-ear adapters on the sides, if one wanted to move it around. The 3D printer clogged, currently in shambles. 

This desk is maybe five percent cleaner.

WIP: Raspberry Pi Build

 

3d Printed Astro-Pi Case

This Raspberry will be my citizen-science build, where I can participate in the scientific research process. These days anyone can volunteer to help scientific researchers answer real-world questions. The Astro-Pi case was designed to fly citizen-science in space, and has room for display, buttons and sensors. The original was machined-aluminum; mine is plastic. I have it wall-mounted on an DIN rail.

It's currently running BIONIC for World Community Grid - which doesn't require any sensors, but I'd like to get a whole space-station's worth of sensors going at some point. The Raspberry Pi supports lots of inexpensive hardware add-ons and free open-source software for nearly any interest - cosmic rays, population ecology, climate and human health, to name a few. 

It's very early days, but another growing area of interest is open-networks. Imagine being part of a public mesh-net that's free. Today most people pay big fees to subscribe to the internet, but someday we probably won't. Mesh networking involves evolving hardware, open-standards, security, and government regulations - fascinating stuff. 

I've always been interested in what a spare CPU could do given enough time, and have frequently used the idea to automate parts of my job. My absolute favorite approach is just to test randomly generated solutions. Imagine the world's least efficient, but dedicated scientist. Employers loved it, and soon they'd be wheeling all the spare hardware into my office. 

        

April is Citizen Science Month, and CitizenScienceMonth.org has a list of events for anyone planning a Citizen Science project or event. Lot's of these projects run on phone apps and don't require any special hardware. Citizen Science is a way to collect data, but also involves the public in scientific issues -getting to choose projects, learning details, and watching the slow march of progress. 

    

Project: Stop-Motion Dude

A post shared by Brian Williams (@exsulto) on Aug 24, 2018 at 10:30pm PDT

Lego makes a decent stop-motion armature for under $20 (kit 75526), and there's free mobile software called "Stop Motion Studio". So I think that means anyone can publish a movie for near zero dollars.

He's much too shiny though. I plan to scratch & paint on him - aiming for the old-robot look.  Also, it might be cool to 3d-print fingers and a face.

MP Select Mini 3D Printer

Disassembled MP hot-end, $10 

In 2016, I got my first 3D printer for $230. Now that I've been through several spools of filament, I'm starting to understand how deep this hole goes. The journey that began with a test-print, then learning some software, designing stuff, has eventually led to tearing into the machine and replacing broken parts.

First the $2 fan stopped. To replace that I found it was a 12v 30mm fan, which is interesting because some expensive printers have 24v, big heaters, larger dual fans. My MP Select Mini is fine for PLA printed slowly (20mm/s), but not for speed or exotic plastics.

I've replaced the painters-tape print bed. The expensive machines have self-leveling, but on this machine I have to remember to do it. It's easy to forget and, not set correctly, the painters-tape got damaged. Painters-tape isn't great at holding prints either; I usually get lift around the edges. The expensive machines use something nicer like removable PEI-steel build plates.

The $2 heat-break clogged. The PTFE tube inside the hot-end bonded with melted PLA and to replace that part is a bit of a hassle; the hot-end disassembles into a dozen tiny parts and the heat-break is in the middle of all that. There shouldn't be melted PLA inside the heat-break. Here the expensive printers do a better job regulating heat, and also at being easy to service and clear.

And it was tricky to align and load filament through all these parts. I'd use sandpaper to round the end of the filament, otherwise it would catch on things. Something like the nicer E3D V6 Lite has a one-piece throat to solve this problem.

E3D V6 Lite in mount adapter, $60

Since the MP Select Mini has some non-standard parts, it's work to find perfect replacements. I find myself measuring parts with dial calipers before ordering. It's a precision machine, and if a nozzle is too big, then it could hit the bed. Monoprice doesn't have much in parts. The expensive machines have name-brand parts, in-stock.

The heat-bed stopped working when it's $1 thermistor quit. Things like nozzles, belts and heater-cartridges, do wear out and will need to be replaced. But in my case, it was these wires under the bed coming apart, so I re-routed new wire through a new 1/2" hole. I've never seen these beds in-stock, so the next fix might mean cutting a custom aluminum plate, with standard heater and standard thermistor.

MP Mini bed re-wire, $0

During the previous events, I discovered a stripped sheetmetal screw. This printer generally has ok hardware where you will see it, and cheap hardware where you won't. Since I don't have a welder, I'll glue-in a twenty-cent threaded insert from HK.

All of this is a long way to understand why something like the Prusa i3 MK3 is $750. I understand there are people that hot-rod their MP Select Mini - I salute them. My plan is only to see how long I can keep this thing printing.

Not everybody is ready for this level of tinkering. I'd recommend this inexpensive printer to folks that own wrenches and screwdrivers and aren't afraid to use them. Consider it part of the entertainment.

Project: Robot Jeep

version 0.3

Update #3: The new frame is 4mm bitbeam plate printed in PLA-plus, which is great because it's metric now. And I have an arduino, motor-shield, and usb battery installed - had to dial-in more power to the motors. Experimentally, 5-volt at 1-amp was only enough juice to run one (type-130) motor.

I tested a fancy E-Flite 7.4-volt LiPo battery (and charger) in this video. The smaller EC2 power connectors are also nice. With the controller set to random movement, heat-sink temp peaked at 140, which is good since the whole thing melts at 205. Looks like the 114:1 gear ratio is still too fast.

The treads are not tracking smoothly - I'm getting binds and clicks around the front sprocket. I need to widen and align the front axle, and maybe print another track design. I'd rather not sand these smooth - maybe I can wear them in. =)

version 0.2

Update #2: I've added a lightweight and inexpensive Tamiya Double Gearbox under the controller - setup for a 114:1 gear-ratio. The Tamiya axle was a quarter-inch too short, so I printed a new sprocket-wheel with axle extension. I'm using a simple friction-fit to the hex-bar rear axle.

version 0.1

Here I test-fitted these 3d-printed tank-treads, and a (temporary) Parallax controller. This project was inspired by the "RC MB Jeep in 1:10" and "Simple Arduino Tank" out on Thingiverse. I've often daydreamed building a full-size jeep out in the garage - so I hope this build can scratch that itch.

Near-term, I'd like simple radio-control and a first-person-view (FPV) camera. Long-term, I'll swap-in a Arduino controller with Android, RobotOS, vision, self-navigation - the whole enchilada.

Vault-Tec Subwoofer 525 Leaked!

I repaired my old powered subwoofer. It died two years ago, loudly, in the middle of the night. It had an internal amplifier that I've replaced with an external Pyle PFA300. While waiting for delivery of the new amp, I patched the old amp holes and painted it.

I sanded the original aluminum plate, glued and screwed quarter-inch plywood behind it, painted, and installed new speaker terminals. I went with a "Fallout" antique theme on the cabinet: flat-black, olive-drab, rust.

Small and inexpensive "Class-T" amplifiers are great for this - they can handle 4-ohm speakers, and a little distortion won't be noticed. My receiver has an active subwoofer line-out, so I don't need an additional cross-over.

For now, I'll only be using one channel of the amp, but it might be fun to try both channels with a fancy 6" dual voice-coil woofer. The existing 20-watt speaker sounds great.

Trigger Testing

#12207E - Northern Flicker
Originally uploaded by Tuzen

It was a clear day so I dumped a hand-full of bird seed in front of the camera robot and set the Nikon on a tripod. This was the first test test of the contraption outside with the critters.

The outdoors are brighter than I had expected, so I see that my sensor math will need adjustment. An unforeseen bonus, however, is that all the images have the same registered background. That will make it easy to photoshop various critters together.

The laser was up near the flicker's head, but the junco was captured about 6" lower because he was moving.  I've read that to capture a bird in flight, I should aim the camera about 1-2 feet past the trigger.

Robot Camera

I have my DIY laser trigger for the Nikon D300s up and running.  A Parallax Basic Stamp controls a small laser, a photo-resistor, and an optoisolator (NTE3222) to the camera release.  The laser bounces off a small mirror to the photo-resistor, and the camera takes a photo when the beam is broken.  The design is a collection of ideas I've been reading about, and parts I have.

In software I need to calculate the ambient light value with the laser off, then calculate the value with the laser on; this creates a perceptible blinking.  I'm starting to think it would be faster if I replace the photo-resistor with a photo-transistor.  Every millisecond counts with subjects racing through the frame.

The laser must be aligned with the mirror and the photo-resistor.  For this reason, a really bright laser would be very helpful when trying to line things up in daylight.  I turn it off right before the camera release, so it won't appear in the photograph.

Desperation of Quiet

Before-LED

After-POT

I picked up a Roboquad toy-robot and started looking for hacks that very night. I was bothered by the lack of volume control. Cracking open the case, I found enough space inside to replace the back LED with a switched potentiometer. It was easy to find the speaker wires since the circuit-board is well labeled. It would've been simpler to disconnect the speaker, but I decided I liked some sound.

I removed the LED and drilled out enough material to make room for the Radio-Shack audio pot. On the front I found the black and yellow speaker wires following from the yellow terminal, spliced the pot into the yellow, tested, soldered and applied red heat-shrink tubing. I didn't have any trouble running my new wires around to the back. It works great; now the volume is adjustable - whew.