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Apartment ventilation system

The 25 year battle to get fresh air in tiny apartments

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The lion kingdom somehow went through college without enduring a lack of ventilation or cigarette smoke, but that all changed in the real world.  The 1st night trying to sleep in a microscopic apartment a programmer could afford, with only 1 window, was brutal.  Ventilation was an expensive perk.  

For the next 3 years, lions relied on small fans in the window to get some minimal air flow, but lions wanted to do better.  It was dusty & most neighbors smoked.  A key requirement was replacing air in different areas of the apartment rather than just near the window, as common fans tend to do.

In 2003, the $35 Hunter 30055 arrived.  With an air duct made from drying machine parts hacked on, it could blow air in any direction & the filter was easy to substitute with any HVAC filter after cutting it to the right size.  It was powerful enough to quickly replace all the air in the apartment.  It's no longer made & today's Hunters no longer have a hackable filter.  



It was used without the filter for many years, before realizing the filter greatly reduced the dust in the apartment & the amount of cleaning of the blower.  After resuming filter usage, the lion kingdom made sure to run it as often as possible, to keep dust out of the apartment as well as for ventilation.

The filters have no effect on cigarette odor, but turn black so they do take out ashes.

In 2006, the decision was made to try to add air ducts from the Hunter to vents in different parts of the room.  While fluid dynamics said the pressure from the blower should be at the beginning of a long tube, experience showed the friction inside the long tubes & leaks absorbed all the air movement.  The blower was placed at the end of all the ducting originally intended to direct the output & the small vent was returned.

When it was new.

4 years later.

The air ducting could store fragrance, but it manely collected spiders.

This served for 8 years & provided the ideal airflow, a directly vertical blast when sleeping & a horizontal blast into any part of the room during heatwaves.  The lion kingdom can't remember ever having trouble sleeping with that airflow.  The problem was all that ducting collected dirt, it took a lot of space, & it required drilling a lot of holes into the walls.

The last iteration is simply resting on a shelf for other things to be stored in.  The intake ducts are just posterboards rolled into tubes.  The airflow is manely horizontal when sleeping, making it less than ideal.  It still manages to replace the air in the apartment, but can't directly blow everywhere.

The Hunter 30055 being 17 years old shows signs of age.  Eventually, it'll have to be replaced.  As simplified as it is from its glory days, every winter involves 6 hours to tear down & clean spiders from every part.

https://hackaday.io/project/169663/log/183826-f-35-nozzle-air-vent

The blower finally got a remote controlled nozzle.

  • Polar vs XY coordinates

    lion mclionhead09/21/2020 at 18:20 0 comments

    Controlling the nozzle in polar coordinates proved to be a real pain.  XY coordinates presented the problem of dead areas where an XY position corresponds to multiple polar positions or multiple XY positions correspond to a single polar position.  An idea emerged whereby dead areas could be avoided.  The key is the fact that the user only moves the nozzle 1 step in 1 direction at a time. 


    For every polar position, we calculate either 4 or 8 adjacent polar positions by adding & subtracting 1 angle & 1 magnitude step.  Then, we manetain a master XY position which updates X if the user presses a horizontal arrow or updates Y if the user presses a vertical arrow while fixing Y if the user presses the horizontal arrow or fixing X if the user presses a vertical arrow.  It picks the next adjacent polar position based on what's closest to the fixed master axis while moving the variable master axis in the right direction.  If 2 polar positions have the same fixed master axis, pick the variable master axis which is closest.

    The next problem was improving the encoders.  It turns out, they actually sense the rising & falling edges of the magnets instead of the magnet centers.  With braking enabled, they actually stop on the rising & falling edges.  The trick is to space the magnets 1 magnet apart & detect 2.5V crossings instead of 0V & 5V levels.  What they can't do is detect the centers of the magnets.  Sensing edges increases the accuracy to 8 steps per turn.  

    Also, the boundary switches don't need to be polled anymore after it's initialized, which could increase the accuracy further.

    The mane problem is the motors are still too fast & reprogramming the encoders would entail making new position tables by paw.  Reprogramming the encoders is just a bandaid for what really needs to be done.  It needs expensive 300:1 motors with built in encoders.  The more lions live with an F-35 air vent, the more reasonable the extra cost becomes.

    https://www.adafruit.com/product/4641

    Further random ideas:

    remote control for the power.

    Aquarium pump powered mister

    LEDs for afterburner effect with the mister.  Mounted on the inside of the nozzle, they could make a straight flame.  The problem is the nozzle rotates, so the water pipe & any wiring would have to slip inside the nozzle.

  • F-35 nozzle air vent

    lion mclionhead09/20/2020 at 06:09 0 comments

    It was the lion kingdom's 1st 3D printing project.  The journey began with much CAD modeling that would later be refined.  Custom C programs made isogrid segments that were too slow to model in Freecad.  The mane limitation in 3D printing is the CAD software.  The whole thing was printed on just the baseline $170 Creality Ender 3 & $20 of filament.  It printed & printed over 7 days while the tower of isogrids grew.

    The 1st part printed by lion was this pinion gear.

      Printing subsections was key to determining the required clearance & minimum gear sizes.  3D printed parts expanded by 0.2mm per side.  2 3D printed parts needed 0.4mm between them to slide past each other.  A structure of this size could get by with 3mm deep gears.

    The bearings & gears were the 1st parts printed.  It was remarkable to see 122 tooth gears like this pop out of the printer after being just dreams for home fabricators for all time.  The bearing parts got 0.5mm of separation to guarantee they wouldn't bind.  The most loaded bearing still needed silicone grease.

    Printing without support or a raft yielded a much smoother bottom side.

    The longest printout was 14 hours for the longest isogrid tube.  Sadly, it lacked a motor mount which later had to be bodged on.

    The boundary sensors used hall effect sensors instead of limit switches.

    Attention then turned to the electronicals.

    So the lion kingdom uses vintage microcontrollers because they look cool, there's an abundant supply in the apartment, the current task needs hardly any computing power, & modern C compilers don't tie your program to a specific chip. It wasn't that way 20 years ago when these microcontrollers 1st arrived. They all have dead pins which are normally labeled.


    Mocking up the cables outside the robot was key.  Wrapping the cable in captain tape & hot gluing the captain to the plastic proved to be the best way to farsten it.  Cable guards were hot glued on to keep the cables out of the gears.  A 6mm diameter proved to be the narrowest PLA worm size before it crumbled. A revision would definitely involve screwing them onto the tubes instead of gluing them.

    Much firmware development followed, manely impacted by the motor control algorithms & the IR code processing.  It suffered from lack of encoder precision & motors that are too fast.  It used leftover polulu #2365 & #2366 motors.  It would have been better with 200:1 gear ratio motors with integrated encoders from adafruit.  

    Inferior motor encoders caused it to be not as smooth as the gootube videos, but good enough to be functional.  Another problem is the IR remote can only move it in steps.  A smaller pinion with no hole for the shaft might have bought more accuracy.  Never tested the minimum wall thickness for a 3D printed gear.

    Mounting it sideways tested the maximum load.  The ideal power supply was a raspberry pi 5.2V.   The motors have very high transient loads when all 3 fire at the same time.  USB phone chargers couldn't manetain the minimum 4V during the transient loads.


     Once installed on the blower, the blower didn't entirely fit in the nozzle, but going halfway seemed to be enough.   It would need to blend into a rectangular isogrid to entirely fit on the blower.


    The IR receiver was repositioned away from the cables.

    The heroineclock remote control got a few more buttons for moving the nozzle.

    It worked as required on the blower.  15 years of wishing for a remote controlled nozzle finally came to an end.  The bearings & contortions didn't impede the airflow as much as expected, but that's why it's a fighter jet nozzle.

  • Practical uses of F-35 nozzles

    lion mclionhead08/11/2020 at 09:28 0 comments

    The search for a better air vent has lasted as long as the fans have been blowing.  Lions have been using semi rigid dryer ducts for 15 years, but they wear out after a year.  At least $200 has been spent on new dryer ducts.  The ultimate vent points in any direction, is aimed remotely like a Tesla Model 3 vent, never wears out, & doesn't rattle.

    Lions found self supporting air ducts on portable air conditioners insanely expensive & heavy.  Louvered air vents only move on 1 axis & are heavy.

    F-35 nozzle designs are 1 of the search requests time forgot.  They give a few videos of home made ones, but not enough to build your own without a lot of suffering.  The current online generation just doesn't care.

    The nozzle is simply an elbow joint from homeless despot.   

    It's the most efficient way to get a directable air nozzle that doesn't wear out & which can be motorized.

    The problem is getting it to rotate smoothly, use servos, & not rattle.  The homeless despot version is intended to be fixed.  It has conical sections which rotate against each other without leaking.  Conical sections are not circular.  They use an oval duct & 3 joints instead of 2, specifically to reduce the eccentricity of the oval shape.

    There are some videos about home made nozzles but no downloadable designs.

    The F-35 nozzle absolutely requires 3D printing.  20 years ago, lions would have written off a project like this as unattainable.  Nowadays, 3D printers are quite cheap, but it will take quite an effort to free up enough space to store one.  The printer's mane task would be printing the F-35 nozzle, but then it would make replacement robot parts, stencils, sandal farsteners, camera mounts, areas which have been stymied by lack of plastic fabrication. 

    At least 2 F-35 nozzles will be made, 1 for injecting outside air & 1 for next to the confuser later on.  An F-35 next to the confuser should take less space than a fan.

    The gootube F-35 nozzles use a magnetic encoder to determine the nozzle position, but this requires persistent storage of the servo position.  They get away with only using it for a 10 minute flight.  If the apartment ventilation always has power, it should work.

    They use a boundary sensor to reset the encoder.


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