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.

The blower finally got a remote controlled nozzle.

  • Blower rebuild

    lion mclionhead10/23/2023 at 01:06 0 comments

    The filter became ripe after another 11 months.  This year would be a full rebuild.

    The filter lets you know it's in need of replacement when the apartment smells like a moldy school library.  After the wettest year on record & a very humid summer, a large nest of spiders had grown in the opposite corner from the inlet.  Some spiders escaped to other areas of the apartment.

    A giant gnat invasion manifested on the other side of the filter.

    After 5 hours of insecticide & washing, the new filter was installed.  Helas, the moldy filter smell was replaced by the smell of insecticide.  The early 2000's design featured many round edges in keeping with the times, making it impossible to seal.

    New weather sealing was installed.  Weather sealing is not adhesive.  It has a mild adhesive for positioning it.  This roll burned $7.

    The speed control features no fiducials so whether high is low is completely random.  This early 2000's design was the epitome of non manufacturability & non user servicability.  There were no user serviceable parts.  The wires had no connectors.  Parts don't automatically align themselves.  Much soldering made it somewhat serviceable.  It was designed to be manufactured only once.  As bad as times are, we're still better off than 2000.

    Fully rebuilding it would take 3 days.  Cleaning the air inlets is another day.  Fully sealing the air passages is another day.

    The question remanes of how to build a custom blower.  The 30055 was originally 110CFM.  The easiest solution is to extract the blower from another Hunter 30055 & put it in a custom enclosure.  There are Hunter 30055's on the fleebay for twice the price of when they were new.  They're more yellowed than this one & probably brittle.

    The Ender 3 can print a 210mm diameter blower.  The bed is not square.  A concept print would take 11 hours & cost $5.

    A thought experiment is whether the original 30055 enclosure would have been better at sealing the filter than the tape hack.  It originally got destroyed to save money on filters before discovering it needed a filter to avoid destroying the motor.  The days of cleaning it after using it without a filter for a year were the days.

  • Toroidal propellers

    lion mclionhead02/10/2023 at 22:09 0 comments

    Manly scott's transonic trussed based wing video triggered a wave of interest in toroidal propellers.

    The thing is, ring wings have been around the rcgroups & gizmodos for 20 years but the message didn't propagate at all until a Manly scott made a vijeo. 

    They're being emphasized just as quad copter propellers, probably because quad copters sell more ads than ventilation fans.  In reality, the extra weight of the joiners doesn't help quad copters.  The mane benefit is in making them quieter.  They could be a good way to make ventilation fans.  A wall of fans which would have been too noisy might be practical.

  • Filter emergency

    lion mclionhead12/27/2022 at 21:23 0 comments

    The pineapple express arrived & the filter became ripe.  Thus began another 1 hour filter replacement.

    There is a desire to grind away these fiddly bits, but other problems are the curved areas.  There could be attachments for the curved areas to make them straight.

    Taping over all the fiddly bits to keep air from leaking takes forever.  Pipe fittings could be printed,for a lot of money.  

    The mane problem with building a custom blower to replace the 20 year old Hunter is the cost of a bare blower.  Large, silent, efficient blowers are expensive.  There's not much left of the original Hunter 30055.  A modern air purifier could be similarly stripped down.  Prices have quadrupled since 2003.

  • Nozzle plan

    lion mclionhead10/16/2022 at 06:46 0 comments

    The unlocked nozzle angle has worked nicely, manely because there haven't been many needs to reset it.  The lion has managed to remember to manually fix the roll before resetting it.  The unlocked nozzle angle has also increased the encoder drift.  There is a plan for achieving higher precision & using quadrature encoders.

    It's going to have 2 fat power wires & a single data wire connected to all 3 motors.  All 3 motors get the same circuit board, which has an H bridge & brain.  The lowest board is stationary, controls all 3 motors, has an LED, IR receiver.  It polls the motors with serial commands.  All the motors have quadrature encoders.  Either the polling has to be real fast, the boards have to buffer encoder ticks, or the motors have to be real slow.  It's believed this arrangement will free up enough wire so it can handle a full 360 deg rotation during a reset if the lion forgets to manually fix the roll.  

    A simulated 300:1 gear ratio looked like an acceptable speed, but it may no longer be possible to turn it by paw.  It might need rotation without reset.  Besides the motors, it needs the H bridges & microcontrollers.  The reserve Atmega328's might do the job but are big.

  • Unlimited nozzle angle

    lion mclionhead09/26/2022 at 17:59 0 comments

    According to the internet, cold air must be blown upwards to displace hot air.  The problem is the nozzle's limited range only allows it to blow down.   Another problem is the air inlet is on the bottom of the window.  The height of the effluxing hot air will have to be studied.

    Getting the nozzle to point up requires rotating the nozzle's inner ring more than 1 revolution.  It can't be tracked with a boundary sensor.  

    The leading idea is now a 2 step manual reset process.  1st, the outer 2 rings are reset automatically.  Then the user uses the remote control to align a fiducial on the inner ring.  The inner ring just has to get within a 180 deg range.   Then the program resets the inner ring as it did before.

    Another theory has an accelerometer on the middle ring giving extra information about the inner ring's position.  This would make the reset automatic.  This involves a lot more wiring.  When the motors switch to quadrature encoders, it might be lighter to put a control board & H bridge on every ring, in which case 1 accelerometer makes sense.

    Another theory says accelerometers can replace all the encoders.  The accelerometers could eliminate all reset procedures.

    Whether or not accelerometers are used, there's still a case where more than 1 revolution of the inner ring could lead to the same accelerometer position.   It would need either a deadband or a manual reset procedure.  The easiest next step is just a manual reset procedure.

    Quadrature encoding may still never happen.  Binary encoding with debouncing has been good enough.

    The current nozzle has 6 wires for each motor.  2 motor power, 2 sensor power, & 2 sensor outputs.  For quadrature encoding, it's finally practical to go with a multiplexing board for each motor with just 4 wires: 1 GND, 1 logic power, 1 motor power & 1 data.  That would multiplex 1 boundary & 2 rotation sensors.  A way to limit current in the motor could get it to 3 wires.

    As problematic as the nozzle is, never forget the 20 years of torture which the nozzle fixed.  

    The decision was made to eliminate all limits on the nozzle angle.  The user has to make sure the motors are all facing down before commanding a reset.  It's a half manual reset.  There's always been an abort functionality during reset.  Press the reset button during the reset procedure to stop the motors.

    The kinematic solver is brutal.  There are 2 sets of limits.  1 set of limits is for the lookup table which translates nozzle pitch to motor positions.  Another set of limits is for the raw encoder values & is tied to the 1st set of limits.  A 3rd set of limits would be required to limit the nozzle angle to a range beyond a single revolution.  The nozzle pitch should be independent of the nozzle angle, but it was written before the kinematics were fully solved.  

    The user has to make sure the cables don't run out of room.  Since most usage is loading a preset & tweeking 1 or 2 stops, it's not normally a problem.

  • Power upgrade

    lion mclionhead08/17/2022 at 00:59 0 comments

    After 2 years, it started resetting when trying to move into certain positions.  Obviously, the motors were stalling more as they aged, causing brownouts.  The decision was made to whack on separate buck converters for the motors & brain with separate grounds.   The dream was originally to run it all on a 5.2 brick, but it was not to be.  A 12V brick was put in.  

  • Video

    lion mclionhead06/14/2022 at 20:39 0 comments

    Finally got around to the movie.

  • F-35 predecessor

    lion mclionhead12/20/2021 at 18:45 0 comments

    Interesting predecessor to the F-35 nozzle built by the soviet union.

    Of note for lions is the use of a torque tube & a complicated mechanism for nozzle opening.  It has 4 swiveling sections & the exit doesn't rotate.  It has a jig which keeps the exit from rotating, thus providing a rigid platform for the last actuator to push against.  It has 3 motors with 1 freewheeling bearing.  The lion version has 3 swiveling sections & the exit rotates.

    It was used in the yak-141

    It had 3 engines.  2 vertically mounted, afterburning engines replaced the lift fan in the nose & only ran when hovering.  Lockheed paid a certain amount for the nozzle design.  It must have been envisioned as a hovering weapons platform.

    1.5 years on, air vent model #F-35 has shown its age.  The front motor no longer has enough brake torque to keep it in a sideways right angle.  Once it slips, the encoders have to be reset.  The brushes must have worn down or the friction in the bearing must have worn down.  Farsteners have started falling off.  It is now known that PLA is threadlock safe.  

    There would be some major redesigns.  Quadrature motor encoding would be the biggest change.  A new nozzle would be built before discarding the old one.  It would have to be manually reset in order to access more range.  

  • Wishlist

    lion mclionhead07/19/2021 at 08:57 0 comments

    The summer heat brought the nozzle's 1st real test.  It definitely needs more range.  The leading idea for adding more range is not using the boundary sensors for detecting runaway motors.  

    Experience has shown the nozzle never needs the boundary sensors & never has to be reset.  It would be too much hassle to completely eliminate the boundary sensors, but they don't have to really stop the motors.

    The fully automatic reset routine can be replaced with a manual reset of the nozzle angle.  The confuser would reset the pitch as before, then the user would manually rotate the angle to within a few steps of the magnet, then resume the reset routine by searching for the precise angle boundary.  It would require no hardware changes.  

    After spending 3 hours replacing another filter, ideas returned for making a complete blower, customized for easy cleaning.  The filter would sit inside an inset notch, making it easy to seal the edges with tape.  The edges would be flat, making it easy to scrape off all the critters.  This one would be made of many smaller blowers that could be individually printed in 1 piece.  The smaller blowers would still be the largest the printer could fit.

    There's a slight benefit to having the exit nozzle change diameter.  The leading plan is having interchangeable nozzle extensions.  The interchangeable extensions just wouldn't be F-35 compliant.

    The whole thing could be made lighter with a year of lessons learned about minimum tolerances for PLA.    The mighty 300:1 N20 motor with encoder is still in stonk.

    Being a much more precise encoder, it would be susceptible to losing count if it wasn't wired in quadrature mode.

  • Misting experiment

    lion mclionhead07/01/2021 at 21:35 0 comments

    This thing does reduce a lion's temperature, when placed right next to an arm.  It's based on early 2000's MEMS investments, a much more efficient solution than a pump with atomizer.  The internet warned it doesn't last long.  If the water isn't distilled, the MEMs atomizer clogs up quickly.  If it runs dry, the MEMS atomizer burns out.  Despite this danger of overheating, it does have a backflow of air to pressurize the tank.  Instead of sensing the water level, it relies on a 5 minute timer to shut it off.

    It runs for around 7 minutes per tank.  It doesn't seem to leak when it's off.  Only a matter of time before the seals start leaking.  There's a high voltage, alternating current driving the atomizer.  A better solution would have a filter & external hose.  At least it's a starting point for a 3D printed mister using multiple atomizers.

    MEMS atomizers seem to have appeared in 2009, near the end of the MEMS boom.  MEMS were the self driving cars of generation X.  They continued evolving into the vaping boom around 2015.  The ideal application was short term use specifically with expensive purpose built fluids.  Along with the essential odor, nicotine or whatever, the fluid could be guaranteed to be free of contaminants so the damn thing wouldn't clog up.

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