Anti-Seasickness Sunglasses

Wear these LCD shutter glasses and enjoy your trip!

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NASA research indicates that strobed lighting conditions may reduce motion sickness, and that LCD shutter glasses can produce similar effects. This project is an experimental pair of sunglasses that might make you feel better as well as look cool.

I, along with another member of my household, suffer severe motion sickness.  So, of course, I bought a boat.  Drugs can combat this condition, but come with a host of side effects, ranging from drowsiness to psychosis.  "You've got that look in your eye again, skipper..."

While researching other remedies, I came upon this NASA report on using stroboscopic vision to reduce motion sickness.  The report indicates that the stroboscopic effect can be produced through lighting or LCD shutter glasses.  I happened to have a few pair of LCD glasses from a previous project, so I figured I'd give this a try.  They're not the most fashionable pair of goggles you can imagine, but if this works, there's no reason an attractive version couldn't be made.

The paper states that flash rates of 4 or 8 Hz with "short dwell times" were found to be effective.  Driving LCD glasses is relatively easy: you just apply an AC waveform to activate (darken) the shutter(s), taking care to eliminate any DC bias which can damage the elements.  For something this simple, there's no need for an actual LCD driver, bit-banged IO on a tiny microcontroller will work just as well.  You can probably find smaller or cheaper solutions, but I have a stash of PIC12LF1571's around which will do nicely for now.  Powered from a coin cell or cylindrical LiMnO2 cell, the battery lifetime should be very good.

EDIT: I just found that these are already a thing!  But, at $123/pair, there's room for a hacker's version that should cost a small fraction of this.

So, the next step is to hack together some code that will flash the glasses at 4 or 8 Hz and around a 90% duty cycle (10% clear).  Then see how it works.  A ride in the back of the car will tell me very quickly if it works.

This project is being released under an MIT license, and the design files for the initial prototype PCB is available in GitHub.



Adobe Portable Document Format - 39.49 kB - 04/16/2018 at 03:52


  • Bit-banging LCDs

    Ted Yapo04/22/2018 at 14:12 0 comments

    The LCD elements in the 3D glasses I'm using for a prototype are normally transparent and become opaque when driven with an AC waveform.  To prevent damage to the LCDs, it's important to eliminate any DC component in the driving waveform; a DC bias across the the elements will eventually damage them.  The PIC12LF1571 doesn't feature dedicated LCD-driving hardware, but for something this simple, the required waveforms are easily generated in code.

    The LCDs will be driven by two pins.  When the LCD is clear, both pins will be low.  To darken the LCD, the pins will drive the elements in push-pull, with an identical number of positive pulses from each phase to ensure no overall DC bias.  A representative waveform is shown here:

    In this case, 5 positive pulses and 5 negative pulses are generated each on the clk_a and clk_b lines to darken the LCDs for 10 periods.  To clear the LCD for 1 period, both lines are brought low, then the cycle begins again, generating a 9.1% duty cycle.  In practice, the switching frequency will be higher than this, so that perhaps hundreds of cycles of AC will punctuate periods of transparency.  This is necessary to prevent flickering during the dark period.

    The actual frequency and voltage level required depend on characteristics of the LCDs themselves.  Since I don't have a datasheet for the prototype glasses, I'll have to determine appropriate values experimentally, but this shouldn't take long.

  • Power Supply and MCU

    Ted Yapo04/22/2018 at 13:41 0 comments

    So, on another project, I've been playing with a power supply for microcontrollers using a single AA or AAA battery.  The idea is to use a low-quiescent-current boost converter to convert the input voltage to 3V to run the MCU.  In that project, I've used a MCP1624, which will will start at a battery voltage 0.65V and once started, continue to run to even lower input levels.  Although there are converters with even lower quiescent currents, the MCP1624 seems well suited to the sunglasses application.

    The design for the current prototype is released under an MIT license, and the design files and gerbers are available on GitHub.

    For a quick prototype, I can use the PCB developed for the 1-cell-mcu project to drive the sunglasses.  The schematic shows how the supply interacts with the PIC12LF1571:

    In the original circuit, the converter charges a large capacitor to power the MCU through long periods of sleep.  The pull-up resistor R3, combined with the tri-state condition of the PIC GPIO pin on reset, creates a fail-safe mechanism to automatically re-start the converter should the MCU not wake before the capacitor fully discharges.  For the sunglasses, this mechanism won't be necessary, since the PIC will be actively driving the glasses whenever the power is on.

    For the sunglasses application, two GPIO pins on the PIC will be used as an LCD driver.  The details will be discussed in a subsequent project log.

    The first prototype PCB has been tested, and works as expected.  A large storage capacitor won't be necessary for the sunglasses, so this part can be eliminated, saving some cost.

    Rough estimates indicate that this type of circuit should power the sunglasses for several years on a single AAA battery.  Although this number is preliminary, it may mean that the sunglasses can be "always on," not requiring a power switch, which can decrease cost and increase reliability.

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Morning.Star wrote 04/16/2018 at 08:16 point

"So, of course, I bought a boat" XD

+1 just for that.

My understanding of motion sickness is that signals from your eyes dont match those from your inner ear and some people cannot deal with the conflicting signals. Your brain actually does lots of things with the information from your eyes besides figuring out what its looking at, taking in information from your entire field of vision. Horizons and relative motion are key in this. When walking, your nervous system is tuned into it, but travelling in a vehicle is an 'unnatural' motion like falling and triggers undesirable autonomic responses from fight-and-flight which your conscious mind tries to override.

That constant struggle between your neural networks is what upsets your brain and makes you ill.

That is an interesting way of getting round it, I think what it does is interfere with the horizon and motion tracking on a subconscious level, preventing them from giving conflicting signals. Motion is interpreted as short bursts rather than long slow movements, which doesnt appear to cause motion sickness.

I get a migraine and hurl if I try and read in a car, but if I look out of the windows I'm fine for hours. Its the vision thats important, it has to be moving with the car and only takes a few minutes to wipe me out...

Dont ask me to navigate or you'll be turning left at the next carrot chunk. XD

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Dr. Cockroach wrote 04/16/2018 at 08:27 point

Same with me, I get sick as a dog on the water and not much better in the air so I bought a airplane and flew for years. Get back on the ground feeling very upset but loving every minuet of it. Ted, you have my like as well :-)

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Ted Yapo wrote 04/16/2018 at 23:29 point

Piloting an airplane would probably bother me: I can swim a lot better than I can fly :-)

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Ted Yapo wrote 04/16/2018 at 23:24 point

I think the problem is a mismatch from the motion sensing of your inner ear and the visual stimulus.  This makes you sick as an evolutionary response: many neurotoxins make you hallucinate before they kill you, so purging when you get these symptoms probably made a lot of sense for early humans foraging for food.

There are some solutions out there that use accelerometers to create an artificial horizon in the visual field (like using google glass), but that's an order of magnitude more complex than this idea.

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Morning.Star wrote 04/18/2018 at 13:29 point

Also explains why a lot of people pop when confronted by something they cant handle mentally. Interesting thought...

I once had a go on a 'SpyroGyro' at a funfair. Strapped to a full 3D gimbal by my hands and feet, and spun in all directions for a few minutes. I loved it, so the bloke span it up laughing most people couldnt take it. But when I got off I couldnt walk in a straight line and eventually threw up ice-cream and burgers. That took a while though, quarter of an hour.

Allegedly the same as zero gravity with most people. We've had two feet for a very long time... ;-)

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