Show HN: I’m Building a Nerf Dart Missile Defense System [video] | Hacker News Reader

Show HN: I’m Building a Nerf Dart Missile Defense System [video]

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175 pointsvpanyam34 comments

I’m building a robot that can track nerf darts and shoot them out of the air.

I’ve worked on other projects in robotics and object tracking (perception for self driving cars), but this has a whole different set of challenges.

Nerf rival rounds travel at over 100 feet per second and shooting them out of the air requires aiming systems that are precise to less than half the width of a human hair and timing precision of 600 times faster than the blink of an eye.

This is the first part of the series of me building the project (and my first video!) so I’d love to hear what you think!

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It's a really interesting video and I enjoyed it -- thank you. A nagging request would be the use of SI units throughout, but I suspect that is an en-us translation issue ;-). [For example, for others, 210 feet per second is about 64 m/s]

Something I might like to cheekily request -- at some point, the difference between v^2 = u^2 + 2as and what you observe will become really quite significant, and I suspect the Magnus effect on both the airsoft pellet will be quite significant. Could you do Schrilen photography and illustrate the air pressure changes at the same time relatively easily with your setup?

I really enjoyed it but I think you can do better.

You did a really awesome job on the script, like really, but you lack animations and footage while talking.

Cut more often to other footage while talking over it, I don't hate your face but illustrations of what you're talking about would help increase viewer attention.

Generally, spend more time on the post-production and editing and afd more animations to explain what you are talking about!

He has done a lot of work with animations and other things. I don't think you appreciate how much time it takes to do that.

I appreciate his content and the time it took to create it. Perhaps I could have done better at conveying that in my comment.

I want to help him retain viewers attention and the additional animations and graphics while talking will increase that.

If time constraints are an issue, I'd suggest to make the videos shorter but more animated.

The post production work is definitely challenging because it's the final part to finish the video and you wish you could skip it all, but it makes or breaks the content. The vision, ideas and script here is amazing but people learn in different ways and educational content like this is best presented in different formats all at once to suit the learning style of the viewer.

The graphics don't need to be amazing, even simple graphics will do the job.

I really like the way you talk through your process, and the way you approach problems. It's very entertaining, and I'm very excited to see more.

I'm hoping to start a new youtube channel myself. I've been surprised a few times by the way my experiments turn out, and I'm not sure I'm explaining well enough the differences between what I thought would happen, and what actually happened.

You did a great job!

Thank you so much!

Good luck starting a channel. I definitely learned a lot during the process of making this video. One thing I found helpful was to write out what I wanted to communicate and iterate on that before filming anything. Maybe that’ll help you get to explanations you’re happy with.

this is awesome. so awesome that it's the first time i've hit the "bell" icon to get notified of new videos.

That’s quite a compliment, thank you!

same thing here awesome job.

Nice [and difficult to implement] idea!

Some time ago I saw this video that attempts an explanation on "how Mark Rober's videos work" [1]. I thought it was pretty good and maybe could be useful for you if you are looking to grow an audience. Good luck!

1: https://www.youtube.com/watch?v=WYXEJ7rDSM0

This is great. My video tips:

1. Edit it down. You need to be brutal (it's painful) but you can start off with the less painful low hanging fruit. E.g. there's no need to mention health and safety at all. You don't need to justify using a PSU. You don't need to explain significant figures or accuracy vs precision in detail. Your audience is interested in technology. You can just say "it doesn't matter if the sights are off as long as the grouping is tight". The video could probably have been 1/2 the length. Easily 2/3.

2. You're a little monotonic. Sorry that's not a nice thing to say and tbh I don't know what you do about it. Tighter editing might help. Also maybe more improvisation of the script?

Anyway I subscribed. Good luck!

Very nice. Absolutely delightful in how undiluted it is. Thank you.

One small request would be to have a way to follow the updates without needing an YT account. An RSS feed (of your blog?), Twitter updates or a simple mailing list would be great.

Try this: https://www.youtube.com/feeds/videos.xml?channel_id=UCIvXdMN...

Excellent, thanks.

Great work. You have great production value for your first YouTube video. Sound, editing, camera, slow-mo. It looks and sounds great. I also think you have a very ambitious and interesting project. I definitely want to see more.

I do have some constructive criticism - but keep in mind that I've never made a successful YouTube channel so I may not know what I'm talking about. I feel there is a difference between the promise of the video (nerf dart missile system) and the payoff of the video (electronic firing mechanism for pellet gun). That mismatch leaves me unsatisfied as a viewer.

For context, when I started watching your video I immediately started scanning with the video scrubber to look for instances of nerf rounds being shot out of the air. I was disappointed not to find any. Conversely, if the video was titled "Shooting pellets from my laptop" or something like that then I would not have been disappointed.

I would suggest structuring each video to follow each specific part of your project. Every time you have a deliverable, give a presentation of that deliverable, the specific part. When you have all the parts, then it will be time for the grand "putting it all together" video where you're shooting nerf rounds out of the sky.

With this approach to video making the first video would be entirely focused on the electronic firing mechanism for the gun. Show the gun, shoot the gun manually, discuss the vertical grouping, disassemble the gun, connect your electronics, and then the "payoff" or climax of the video is you shooting the gun from your laptop. Anything that distracts from the plot, that is, taking the audience from pellet gun to electronically fired pellet gun, should be cut from the video, unless you absolutely need it for future context (e.g. measuring the vertical grouping).

I would think about the video as like writing. Points that distract from the central message should be pruned. One example - your aside on microcontrollers. I think it's a fair bet that the kind of person who would watch this video already has a good idea what a microcontroller is, but even if they didn't, they would be very likely to infer that it is essentially a small computer from context.

I see you start the digression on microcontrollers at 10:37 and complete it at 11:00 - that's 23 seconds where you are essentially going away from the central idea of the video. This is just one digression. How much time could you cut from the video if you eliminated all digressions and made a tight focused video specifically on the deliverable?

A video that is concise and concentrated on message and delivers what it promises to the audience will, in my estimation, retain and please viewers. High audience retention will help you with the YouTube algorithm getting your video recommended to others.

Final suggestion - start with what you've built. i.e. Start by shooting the gun from the laptop, just a couple shots, to show the viewer you are going to deliver what your video promises, then walk through the process to finish up where you started - with the complete demo of the computer controlled firing process.

I watched the video from start till end without rewinding - what is unusual - and I was disappointed only by lack of following parts. I wish, I could shot flies with drops of washing liquid in similar way.

Wow, thank you! I’m glad you enjoyed it :)

If you can ever build a mosquito defense system like that, the world will beat a path to your door.

An attempt has been made, at least.

https://www.youtube.com/watch?v=BKm8FolQ7jw

First off, thank you for taking the time to write this. I really appreciate the feedback.

I agree with some of your points and in fact I was originally going to post the video with “[part 1]” in the title, but I decided to leave it out and rename it when I post part 2. I figured this was fine since I say “this is the first part of a series” in the first 30 or 40 seconds of the video (and also included it in the HN post description).

I do agree with the idea of having a focused cohesive theme to a video, but I didn’t really find a natural spot to cut it that didn’t make the video boring or not provide the motivation/context of the end goal (eg “firing an electronic airsoft gun from a computer” isn’t conveying what I want to convey).

The goal of this series is to show the process in detail instead of just a high level overview. I’m hoping to post a high level overview video at the end that’s more appealing to people who don’t necessarily want to dig through all the details.

I think future videos will be a little more scoped because they don’t need to include an in depth project overview. Kinda a focused story within the context of a larger backdrop.

I do agree with the point about audience and I think that’s important in general. However, I think there are several things that seem simple and commonplace, but may actually be important to talk about briefly to make the content more accessible for people who don’t have context on a particular area I’m diving into.

Thanks again for the feedback and I’m glad you enjoyed the video!

Heres an elegant approach when it comes time to do the aiming system. First, switch to metal pellets. Second, use electromagnets just after the muzzle to curve the trajectory right as the flight path begins. Aim it by adjusting voltage exactly the same way old crt televisions aimed the electron beam. No moving parts, far far faster adjustments than your 200 ms restriction, as many bits of precision as you can fit on your DAC, and won't add vibrations that add into your error bars.

That's outstanding!

I particularly liked your talking about your approach to solving problems. (Hardest part first, build tests)

Looking forward to part two!

Good luck!

I highly recommend watching the video from Stuff Made Here where he builds a bow "aimbot" to hit targets mid-air. Very similar problem.

https://www.youtube.com/watch?v=1MkrNVic7pw

I think the speeds and sizes of the ammunition and target will make things different enough. also at a scale this small would wind/air movement be a major enough source of potential problems if you don't measure it ?

Yes, airsoft is heavily affected by the wind. Each shot lands in a different place from numerous additional factors, too. They are very different performance-wise compared to guns.

This is fantastic. Really love your calm, investigative tone. Look forward to part two.

Thank you so much!

This is great. IMHO, this first video is already up in the ranks with other channels like Stuff Made Here, Clough42, and Breaking Taps. Excited to follow this project's progress and whatever else you come up with :)

Great Video! I love how systematic you are with your testing. Instant subscribe!

This is really awesome, in all seriousness you could maybe sell this to Nerf

Thank you! I don’t have any particular outcomes in mind, but we’ll see what happens!

This is excellent. Your approach of solving the hardest problems first is great engineering. Looking forward to the rest of the series.

Thank you!

Why do you constrain yourself to a single pellet? It may be simpler to shoot ten pellets at a time than stabilizing the barrel.

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