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Show HN: Alzheimer's Buddy: Use Flashing Light and Sound at 40Hz

alzheimersbuddy.com

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Re: Show HN: Alzheimer's Buddy: Use Flashing Light and Sound at 40Hz

#81
This is funny. Just this week, I've been thinking about simulating a Dreamachine[1] in software.

Isn't the obvious solution to your timing problem to distribute it as a video file instead? To be played on 120Hz-capable hardware, obviously.

[1] https://en.wikipedia.org/wiki/Dreamachine

Re: Show HN: Alzheimer's Buddy: Use Flashing Light and Sound at 40Hz

#82

Given the problems people are having with their monitors, and the inherent issues with timing on a 60hz screen and timing on a enormous mass of abstraction... Using a microcontroller with a DAC and a LED array seems particularly well suited for this, while still being firmly a beginner level project.

Does 50hz work? If so, just use an incandescent light bulb?

Re: Show HN: Alzheimer's Buddy: Use Flashing Light and Sound at 40Hz

#83

Cool concept and project. I don't know if browsers are capable of doing the flash reliably. I tried it out (non-epileptic and curious), and you can see that it's not a reliable 40Hz flash on either Chrome or Firefox. I haven't looked to see what technique you are using for the timing, but there's quite a bit of jitter. EDIT: it's using requestAnimationFrame. Rather than using that, have you tried using CSS keyframes?…

Whether it's RAF or CSS, this would only reliably work on a 120hz display (or anything else higher than 80hz and divisible by 40.)

Just higher than 80Hz should be enough via Nyquist's theorem, or no?

Re: Show HN: Alzheimer's Buddy: Use Flashing Light and Sound at 40Hz

#84

Given the problems people are having with their monitors, and the inherent issues with timing on a 60hz screen and timing on a enormous mass of abstraction... Using a microcontroller with a DAC and a LED array seems particularly well suited for this, while still being firmly a beginner level project.

Shouldn't really need a DAC, just use the PWM output. Any $5 microcontroller should be able to do this with some reliability. Heck, the PiPico has programmable IO which could do this without the processor. Or hey, a 555 timer with the right resistors and capacitors would do the same thing.
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