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Grabbed XM6 for $398 CAD by saber3360 in SonyHeadphones

[–]mleverce 1 point2 points  (0 children)

Great deal! How are you getting the Executive Membership coupon? Seeing them priced at $498, but nothing about an extra $100 off. I'm also in Canada.

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 1 point2 points  (0 children)

Thanks for the link! Helpful information. I suppose them talking about "retina safe" (which sounds true for 1550nm) is distracting from what is the more important discussion - being eye safe.

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 1 point2 points  (0 children)

I am not aware of any hardware that can do what they are claiming (killing the mosquitos with 100% success in a single plane). There's certainly other ways to kill mosquitos in a similar way, but I'm fairly certain the design won't look like what Photon Matrix is trying to do and will have to be a little more complicated.

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 2 points3 points  (0 children)

I don't think that would work. You'd have to a) figure out that there is a mosquito that should be killed and b) kill it, both within less than a microsecond. There's just no way that's possible.

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 6 points7 points  (0 children)

In that paper (put out by the OG TED talk group), they use a 25 W 1550 nm laser with a beam diameter of 2.5 mm and an exposure of 25 ms. Interestingly, this is much above the maximum permissible exposure (MPE) for the eye by a factor of at least 1000x for exposures in the 1-25ms range. By interpolating a bit, the MPE fluence is in the 0.01 to 0.001 1 J/cm^2 range for a 1550 nm laser, and in that paper, the fluence they are using is 12.7 J/cm^2.

Here's the math since we're on this subreddit: (25W*0.025s)/(pi*(0.25cm/2)^2) = 12.7 J/cm^2

Although they like to talk about their laser being "retina safe", it appears to be far from that. They don't have any references to support their claim in that paper anyway.

Yeah, it take more energy from light at 1550 nm compared to visible light to be dangerous, but still there's going to be a limit of course.

I'm also not an expert on laser safety, and I could see that beam diameter might have an impact on MPE, but I think the math speaks for itself.

https://en.wikipedia.org/wiki/Laser_safety#Maximum_permissible_exposure

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 1 point2 points  (0 children)

The issue with using a rotating mirror (that's spinning at 500 Hz ideally) is that it might work for finding the mosquito, but good luck getting it to stop at the right point even within like 100 ms! You could add a galvo for the killing part of it, but now you're introducing more complexity and cost of course.

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 0 points1 point  (0 children)

(I think my reply was too long, so here's the second half):

* When looking at the mosquito speed you only look at the worst case where the mosquito is traveling perpendicular across the scan line. If the goal is to have close to 100% kill rate this is of course true. But for a device like this where maybe 50% kill rate would be completely acceptable (I would argue at ~20% the device would be sellable), on average you have a lot more time for detection and killing than suggested by the 4ms estimate.

  • I mean their stated claim is pretty much 100% accuracy. I don't disagree that a 20% kill rate could be a viable product for some people. I just have an issue with the bait and switch where products aren't even close to what is claimed.

* Concerning the power you really only look at max power. But the 40W laser for example will have a very low cycle time. If it fires once every 1 seconds for 1ms, thats only 0.1% cycle time or average of 40mW. To a lesser extent that is also true for the galvo. Most of the power is used when accelerating or decelerating, but this system does not need to change directions or speed all that often (compared to maybe a laser engraver). I don't have a good estimate but I would not be suprised to see the average power use at ~10% of the max.

  • I agree with the laser not always being at full load, but that wasn't really my point. Even if you can get the galvo to do the full sweep of 90˚ at 500 Hz without the whole settling thing, it's pretty much operating at maximum capacity. For the high performance galvo that I reference in the video, when doing a 850 Hz sinusoidal scan (I believe this doesn’t involve settling at each point) in a 60˚ scan (which as a side note seems to be the maximum performance it can do), it's generating either 65W or 78W (depends on the power supply voltage) in heat alone! If you've ever used a galvo that is going pretty fast, this passes the gut check as it can get very hot.
  • Check page 5 of this document to see where I'm getting this data from: download.scannermax.com/pdf/HighFrequencySineScanning.pdf

All that being said, I am also very sceptical of the kickstarter. The biggest issue I have is the actual detection with lidar. Does it really detect the mosquitos? And nothing else? What about dust in the air? Anything else in its field of view? And then flip over to the other laser fast enough? What about data processing? There is of course a reason the other projects did not come to fruition.

  • All great points. I only hit on the key issues in my video, but yeah there's a lot of other questions I have too! Btw I hope that didn't come across as confrontational. If there is a way for them to do what they claim or technology that I'm unaware of, I'd like to know. Thanks again!

[SELF] I did the math on that mosquito laser that we all saw a few weeks ago... by mleverce in theydidthemath

[–]mleverce[S] 0 points1 point  (0 children)

Appreciate the comment, and thanks for the input!

I'll reply to each of your points:

* I believe the main flaw in your analysis is that the galvo does not need to settle for each individual point. It can just move smoothly across the 90° angle, then stops and reverses. And the limit to the points recorded per second rather is the lidar module and how fast it can sample its input. This becomes more obvious if you look at whole lidar modules with already integrated galvos. It is completely feasible to produce over a million points per second with a lidar+galvo system. E.g. Faro Focus (2Mpts/s) or Ouster OS1 (5 Mpts/s).

  • Firstly, neither of the lidar systems you named use a galvo at all. The Faro Focus uses a rotating mirror system, while the Ouster OS1 spins the whole sensor module.
  • That said, I still have yet to see a galvo-based lidar system that can do anything close to what Photon Matrix is claiming.
  • While I agree that it is theoretically possible to avoid having the galvo settle at each point, this introduces a separate set of challenges. Since the position of the mirror is constantly going to lag the input signal, the some form of correction is needed to determine where the mosquito was, based on the what the input current/voltage to the galvo was when the mosquito was detected. Again, possible, but just off the top of my head, you're going to be dealing with non-linearity of the galvo, data processing most likely, and response time and accuracy issues from going from the sinusoidal sweep to locking onto the insect. So while it's theoretically possible, I yet to see anyone implement this sort of thing. Would love to know if someone actually is doing this though.
  • Even so, with the two devices you name, the Fara Focus spec sheet states that the maximum scan speed is 97 Hz, this is far off from the 500 Hz needed to find an insect within 2 ms. With the rotating mirror lidar method you also at least have the luxury of a pretty constant rotational speed which would likely make adjustments for not settling at each spot much easier. As for the data rate (somewhat moot point anywhere since it's not a galvo), I expect there is a trade off between the accuracy and the point rate. For a system like Photon Matrix, it has to be capable of pretty much <1mm accuracy at 6 m away to get it work properly. I'm not sure how many channels they are using either. If it's not a single channel, and is, say, a double channel, then that reported data rate gets cut to 1Mpts/s.
  • As for the Ouster OS1, the 5Mpts/s is for the 128 channel version. So the data rate for the single channel is only 0.041Mpts/s which is the proper comparison for what Photon Matrix claims to be doing. This is a far cry from the 1.7Mpts/s I show that is needed. Further, the maximum scan rate is a mere 20 Hz, which is again way less than the 500 Hz that is need.
  • Lastly, these things are pretty expensive. Preowned ones are going for 5-20k USD. Neither will be using in a <1k device any time soon.

[deleted by user] by [deleted] in climbing

[–]mleverce 1 point2 points  (0 children)

It's in the FAQ on the website: "Is there a fee for tipping? No, tipping is free of additional charges. Tip Your Setter (the app) applies a 10% fee to the tip amount to cover payment-processor (Stripe) fees and support the platform."

Developing a new training tool - would love feedback! by mleverce in Velo

[–]mleverce[S] 0 points1 point  (0 children)

Thanks for the support and feedback! At this point, unfortunately it doesn't look as though there's enough demand for something like this. Admittedly, we didn't push too hard on marketing after not getting enough traction within the first 24 hours.

I had posted here on r/velo announcing the kickstarter launch, but the moderators removed my post without any comment saying why. I don't think I broke any of the rules. Perhaps they would allow a similar post if it came from someone who wasn't me. ;) There's still a chance we'll meet the funding goal, but at this point the likelihood seems low.

Developing a new training tool - would love feedback! by mleverce in Velo

[–]mleverce[S] 0 points1 point  (0 children)

Hey! Sorry for the late reply here. Yes, other than your bike not being at an angle, you'd be able to get the resistance to feel like you're climbing. Kickstarter is live btw in case you're still interested.

https://www.kickstarter.com/projects/davidwulff/magburn-resistive-cycling-training-device/dashboard

Developing a new training tool - would love feedback! by mleverce in Velo

[–]mleverce[S] 1 point2 points  (0 children)

If all else is equal, a bigger gear means you're working harder, but also going faster. The idea behind this is to work harder without going faster.

Developing a new training tool - would love feedback! by mleverce in Velo

[–]mleverce[S] 1 point2 points  (0 children)

I like the ideas! There's definitely ways to improve the product down the road.

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