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Solar filament drier

How to keep filament dry while being too poor to afford electricity.

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The lion kingdom considered many ideas for drying filament involving peltier coolers which could be repurposed for atmospheric water generation.  The simplest solution has converged on a simple solar heated container.

The general idea is a transparent container just big enough to enclose the filament.  There would be 2 vents with air tight valves.  There would be a fan on the inside to circulate air & a fan outside a vent to force outside air in.  There would be a dewpoint sensor inside & outside.  The electronicals would be manes powered, but all the heat would come from the sun.

The inside fan would always be on.  The outside fan would turn on & the 2 vents would open when the outside dewpoint was lower than the inside dewpoint.  

This would entail ordering 3 humidity & temperature sensors.  1 extra would go to a readout on the lion kingdom's weather wall, in order to find an ideal time to use the filament.  

The mane problem is air tight valves big enough for a fan.  They must be air tight when the outside dewpoint is higher than the inside dewpoint.  The lion kingdom is keen on using its 2 Nidec blowers from 22 years ago.  They have small outlets which would reduce the valve size.  

The easiest solution might be an aquarium air pump

https://www.amazon.com/Pawfly-MA-60-Aquarium-Gallon-Accessories/dp/B073DWVX5P

& aquarium check valves.

https://www.amazon.com/Pawfly-Aquarium-Valves-Plastic-Non-Return/dp/B01N92AXHF

The valves could be closed by gravity when the pump is off, but they may only be water tight instead of air tight.

Valves closed by gravity & opened by air pressure would still be ideal.  Lions haven't had any luck with flaps of material.

Adafruit has an air pump.

https://www.adafruit.com/product/4700

& air valve.

https://www.adafruit.com/product/4663

Temperature & humidity sensor:

https://www.adafruit.com/product/4566

Airtight container:

https://www.amazon.com/Rubbermaid-Storage-Container-Racer-1777161/dp/B000WEMFOS

This was the best match for a 1kg 60x200x200mm roll.  It stretches slightly to make it fit.

The tubing is the same 3mm ID silicon tube that the lion kingdom got for its humidifier air conditioner.  There's still the problem of making an airtight seal between the tubes & the filament container.  It might involve printing farsteners which can be stuffed with a lot of goo.

Of course, the cost has to be weighed against buying a new roll of filament every time it gets wet.

  • Matterhackers PRO TPU

    lion mclionhead07/25/2022 at 06:28 0 comments

    Threw the roll in for 8 days & it printed about as well as the others.

    All TPU filament is coming out with voids, but less voids than no drying.  Doing any better might just require a heater on the printer itself.

  • Triac round 3

    lion mclionhead07/05/2022 at 07:41 0 comments

    After continuing to intermittently fail on, a 220k was put between gate & neutral to pull it to neutral.  The lion kingdom observed that probing gate's voltage turned it off.  The 1 meg resistance in the Fluke might have been enough to pull it to neutral.  Now the meter said there's 2k between the gate & neutral by default.  Not sure why that would be if the optocoupler was off & the gate is high impedance.  The optocoupler may well be defective.

    This got it turning off again, but reinstalling the snubber circuit made it fail again.  The snubber never did work.

    The next step would be a bag of triacs & optocouplers.  A triac is much cheaper than a relay so lions would rather keep bodging a triac than solve the problem with a relay.

    Another thing lions learned is resistances need to be a lot bigger at high voltage.  The word pullup conjures up visions of 10k resistors, but at 120V that burns 1.4W & starts a fire.  220k is a more useful pullup resistor at 120V.  

    A few weeks with the pulldown resistor yielded stable dewpoints & low humidities.  The summer has much higher humidity than the winter & much less sunlight hitting the container.  Being much quieter, the aquarium pump runs all afternoon without a timeout.

    It could almost run based on solar panel output instead of hydrometers, but lions fear the slight loss of efficiency would cost it like the passive valve idea.  The filament gets hot enough that the air circulator never turns off.  Inside air temperature never drops below outside air temperature in the summer.

    The next frontier is disabling the air circulator.  It should only run when turning it on would cause the filament to release water instead of absorb it.  The only way to know the filament can release water is when the inside dewpoint is rising or above ambient.  Activation of the pump creates an unknown where the inside dewpoint is falling while the filament is still releasing water, so we have to wait until it's below ambient & falling to be sure.

    The derivative of the dewpoint might be the key.  It just requires the filament to already be releasing water to know if the filament can release water.

  • Aquarium pump upgrade

    lion mclionhead06/19/2022 at 21:30 0 comments

    So then there was this 10-20 gallon aquarium pump.

    https://www.amazon.com/gp/product/B0009YJ4N6

    It does have an inlet which generates a vacuum, but the difficulty of connecting to that inlet led to another use as a compressor & hope the container didn't explode.  It doesn't need a 1 way valve to manetain a seal.  It's just a simple 4k ohm solenoid which oscillates a ferrite magnet.  It burns 2.5W at a .95 power factor.

    The great challenge was turning it on.

    https://www.amazon.com/dp/B07P6HX85G

    This thing is based on the BTA41-600B Triac & MOC3021 optocoupler.  The 1st problem was it not turning off.  Removing the 10 ohm snubber resistor was the only way it would turn off.  It could be the 2.5W load wasn't enough to turn it off.

    The other problem was a lack of desire to have a live load when it's off.  As originally labeled, the load was always live & the neutral was switched off.  It actually works if live & neutral are reversed.  To make this arrangement work, the line has to plug in to the triac side.  The line provides the voltage to turn on the gate.  This might not work for inductive loads which require the snubber circuit.


    Enclosing the new mess of pumps & electronicals will require a 3D printed enclosure.  As hoped, the pump is totally silent.  Unfortunately, the 10 gallon aquarium pump was nowhere close to as powerful as the inkjet pump so daytime dewpoints ran away.  The most efficient drying happens when the inside dewpoint is as low as possible during the highest temperatures.  There shouldn't be any water hanging around above the ambient dewpoint.

    There are delusions of rewinding the solenoid to run on lower voltage & higher current & higher frequency. The only real capacity change would come from a bigger pump.  The volume of air is limited by the mechanics.  Bigger aquarium pumps take more space, cost more & are louder.  

    2 days showed it pulling more water out than the passive valves but not as much as the adafruit pump.  At least it was silent.

    A 40 gallon pump quickly replaced the 10-20 gallon one.  It was just as silent but had comparable thrust to the inkjet pump.  It burned 3.5W.

    Interior dew points were pulled right down to exterior dew points.  Unfortunately, it still requires 120V.  After 9 days, the triac failed on again & it started pumping in water instead of pumping it out.  By this time, the lion kingdom was leaning on a defective triac. There could be 1 more attempt at a pulldown resistor between the gate & neutral but the mane idea was to buy a bag of triacs & a relay.

    The next problem is the CPU fan as a circulation fan is dying.  There's no way to lubricate it & it's not up to the conditions in the dehydrator.  CPU fans are intended to blow cold air at a hot CPU, not circulate hot air.  A more serviceable blower is needed.

  • Vacuum pump 2

    lion mclionhead06/11/2022 at 07:16 0 comments

    Installing the tubes for the 2nd time in a new container, the lion kingdom noted some essential techniques to get an airtight seal.  Melt the plastic & sand the edges to make holes.  Cutting with an xacto or drilling cracks the plastic.

    The new holes went right against the lid.

    Install the inner components 1st.  Mark which way is up.  Melt them all to conform them to the inside shape.  Then apply Loctite clear silicone to all the inner components & press them in place.  Only after all the inner components are loosely adhered in place, slide the outer components on.  Melt them to conform them to the outside shape.  Apply CA glue to bond the 2 pieces after everything is in place.

    To get the best silicone seal, the outer pieces have to slide on loosely.  Melting the outer pieces stops them from sliding loosely.

    The lion kingdom has a PLA hydration problem.

    Silicone was stuffed in the wiring hole.

    The pump was stuffed between some stuff in a box to try to quiet it.  This was not really any quieter.

    Hoses used normal 1/4" drip tubing, which allowed many right angle connectors.

    The rebuilt pump MOSFET got no flyback diode or pulldown resistor.  The fuse resistor might reduce the flyback current.

    Humidity was pumped back down to 30% below ambient.  Dew point was pumped back down to below 0.

    After a few days of pain from that pump running continuously all afternoon, attention turned to a silent aquarium pump.  Silent vacuums don't exist.  It has to be a pump.  They all use 1/4" tubes & manes voltage.

    https://www.amazon.com/gp/product/B0009YJ4N6

    A thyristor is required.

    https://www.amazon.com/Module-Thyristor-Control-Trigger-High-Power/dp/B07P6HX85G/

    The pump has to go in the inlet on the bottom.  The outlet tube now has to wrap over the top.  There have to be 2 manes plugs.  

  • Dual valve upgrade

    lion mclionhead06/02/2022 at 07:09 0 comments

    Driving them off the same PWM does work.  Get the confuser to close the valves before installing the servo.  Then install the servo in the closed position with slight tension on the TPU.  The valve closes by turning counter clockwise, so the TPU has to be twisted slightly in the clockwise direction.

    There was no way to put the 2nd valve any lower than half way, so it went as close as possible to the circulation fan.  The mane problem with valves is the inlet air is much warmer than the outside sensor.  The sensor can't go near the heated container.

    A week of drying showed a 10-15% difference in humidity being manetained & no difference in night time dew point being manetained.

    The last set of data with the pump showed a 20-30% difference in humidity during the day & nighttime dew point pulling 10 deg below ambient.

    https://hackaday.io/project/183147/log/206421-changing-pumps

    This proved the air seal with the pump made a difference.  The valves are no match against the volume changes of the air.

    The next task is reconstituting the pump system & making it quiet.  Despite its tendency to stay on all day like it wasn't working, it actually was working better than than the passive valves & it's already paid for.  The times when it came on at night were only when a cold front moved through.

  • 3 days of butterfly valve drying

    lion mclionhead05/30/2022 at 21:30 0 comments

    3 days of data showed the passive valve achieving humidity 5% higher than the active pump.  

    Both devices kept the inside temperature above the outside temperature.  The mane problem is the passive valve doesn't replace the inside air as much as the pump.  Inside dewpoint is allowed to rise higher with the valve, but it still has limited ability to clamp the dewpoint.  Inside temperatures didn't get as high, probably because the valve isn't air tight.  A small fan blowing air down half of the valve would replace more of the air.

    The results were a bit too degraded to live with so forced air started gaining favor again.  There was the idea of a non self supporting air duct made of 3" poly tubing but poly tubing in small quantities is extremely expensive.  

    The alternative is taping bits of polyethylene together to make a tube.  It's not air tight & it doesn't create a seal against the blower.  The types of blowers which are silent don't generate enough static pressure to inflate the tube.  Between the lack of air pressure & the leaks, the tube has to be self supporting to move any air.

    It might be good enough just to have a 2nd butterfly valve on the bottom of the lid to let cold air in.

    At least it yielded a nice adapter.  3 years ago, an adapter like that would have entailed many trips to the homeless despot, bodging together random vacuum cleaner parts.

  • 3D printed butterfly valve

    lion mclionhead05/25/2022 at 00:29 0 comments

    A solid week of banging on CAD models yielded a butterfly valve.

    This was the 1st to directly couple a PLA shaft to a servo shaft.  To start with, it uses friction.  It could resort to CA glue.  To achieve a static pressure on the valve, it relies on the servo supports applying a static spring pressure on the torque tube.  The servo powers off after 5 seconds to avoid wearing out the motor.  There's no sensor for valve position, so it could get stuck in 1 position.  

    The latest idea was a container with just 1 big valve.  The inside air should get hot during the day.  When the valve opens, the hot air leaves & the cold air enters.  At night when the container is colder than ambient, no air is replaced.  The valve is not as air tight as the former tubes.  

    The board got converted back to 5V, a MOSFET got taken out, a PWM driver got put in. 

  • Changing pumps

    lion mclionhead05/23/2022 at 03:35 0 comments

    The old pump pulled down the humidity to the 20's.  The indoor swamp cooler didn't affect the humidity near the window.

    The decision was made to replace the pump, after a very noisy final TPU drying.  Lions have lived in a very noisy environment for 25 years, with confusers, atomizers & fans, but the inkjet printer pump was a uniquely difficult noise.

    After taking out the fuse connection & the stall LED, it became quite clear that the 3/4" ID tube was never going to have an airtight connection on top & it was never going to navigate the tight corners.  The angle connectors might have hope with narrower tube, but narrower tube requires a noisier pump.  

    The easiest fix with this design is going back to 1/4" tubing, using store bought barbed farsteners, & just enclosing the inkjet pump in something soundproof.  The inkjet pump turns out to fit 1/4" tubing better than 3mm tubing.

    Another idea is an air tight barn door on the side with no tubing or pump.  Position the circulation fan near the barn door.  When the inside dew point gets high enough, open the barn door & rely on the circulation fan to replace all the air.

  • New pump

    lion mclionhead05/12/2022 at 19:44 0 comments

    The blower they said could never be mounted on anything 25 years ago finally was fixed to a tube.  Through 2 ft of 3/4" ID tube, the airflow was greatly reduced but still useful.  It needs 12V to move any air through.  The tube could be doubled up.

    Only a tiny flake of the original 90's Gamma 28 label remanes.  

    Another key development besides mounting the blower was printing an elbow.  The only way to do it is to print an octagon sideways.  Each end of the octagon needs a separately printed adapter to attach to whatever it's attached to.  Holes were melted in the tube for farsteners.  It's tight enough to not need nuts.

    By now, it was clear that the new blower would make the dehydrator much bulkier & heavier.  A new surface mount board could fit directly on the blower & greatly shrink the window usage.  The wiring would have to go through a new orifice near the pump.  The pump doesn't have to be air tight.  Then there's the problem of balancing the container on the window.  

    The simpler solution is to keep the existing wiring in a container orifice, but the size requirement ended up making the lion kingdom go back to the inkjet pump.  To change to the blower pump would require moving the electronicals to a surface mount board on the blower.  Then, it would take less space than the inkjet pump.  The space constraints of having a job make it hard to use all of the lion kingdom's through hole parts.

  • New TPU roll

    lion mclionhead05/10/2022 at 17:51 0 comments

    A full 1kg roll arrived wet from the factory, so it went into the dehydrator for 7 days.

    Most of those days were cloudy, but temperatures & humidity were higher than winter.  The dried filament still did a lot better on a part than the new filament.  It wasn't perfect, but it was good enough to not bother enhancing the drier.  

    Lions have found filament which isn't on a roll doesn't dry at all.  It seems to absorb water from being handled by lion paws.  

    The dehydrator has problems.  Blocking the inlet doesn't slow the pump down, so it's not very air tight anymore.  The pump is real noisy, now runs all day continuously, & turns on at night when the roll is fresh.  Waking up to the pump is brutal.  The pump has a duty cycle to limit the noise, but lions don't care if it wears out.  The best it can do is reach a constant equilibrium where the humidity is always lower on the inside than the outside & the filament is heated for part of the day.  

    There could be leaks where the tubes enter the container or the container itself could be keeling over.  That was the only container a lion could afford.  

    The plan is to replace the pump with a vintage Nidec blower.  Use the largest clear tube which is flexible.  Print right angle connectors & a connector to the blower.  Route all the wires through the air tubes.  The 1st step would be measuring how much air the blower can force through a tube of a certain diameter.

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crun wrote 05/27/2022 at 22:39 point

A very simple passive valve is a tube of polythene (i.e a plastic bag) or nylon fabric, with it's axis horizontal, and a vertical flange plane at one end. When you turn the fan on, it straightens out and air flows. When you turn the fan off it folds over and closes.

This works better arranged as a long flat tube than a round one. Fortuitously this is kind of how ziplok plastic bags already come.

These can be better than a flap valve, where it is quite hard to get a very light flap to seal when closed.

Quite a good way to collect solar heat is to suck your inlet air through a black fabric (that the sun heats). You don't need a cover glass, because the thin layer of heated air on the outside is being sucked in, instead of being lost when you have a solid black surface. It could also be a dust filter.

I would think that only very low flow rate would be needed, so perhaps just having a solar panel inside the box directly connected to a small fan would do the whole job

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