Coil Gun Speed Meter

_DIY_bullet_speed_meter (Custom)

One of the best parts of building a coil gun is seeing just how fast you can get that slug to move through the air. [Daniel] built this speed meter to be able to see exactly that. It is comprised of two optical sensors, one at each end of a barrel. As the projectile passes them, its speed is calculated using an Atmega16. Since the distance between the sensors is pre determined, its only some simple math to figure out the speed of an object passing between them. The result is then displayed on a nice looking blue LCD.

If the blue accent lighting and acrylic stylings look familiar, that’s because we’ve seen [Daniel] before. He’s the one that built the portable coil pistol.

[via HackedGadgets]

28 thoughts on “Coil Gun Speed Meter

  1. Why are guns so important to HackDay? I know people will argue that it is a toy. Try to explain this idea to an officer through airport security. May be a toy, but has a strong subliminal purpose in the back… bad practice hackaday!!! stop showing these types of toys…

  2. My impression of hackaday was that it is not about safe toys, it’s about interesting hardware and software hacks. Many things on Hackaday, like the instruments that use fire or jet engines or high voltage Tesla coils are not toys. If you don’t like dangerous stuff, don’t read about the hack. Back on topic: I’m really pleased with hackers who include their schematics and eagle drawings. It’s awesome when people are willing to share their hard work with everyone. This is a cool idea, and could be useful for a variety of speed-checking applications with a change in layout.

  3. I agree with TNTC and agree that the site and the project is well documented, and I like that. Kudos for that. What I do have a problem with is when I see guns. Again, it gives the wrong impression and definitively carries a subliminal message, although for sure not intended by the author of this device. I simply have something against guns and those who use them for fun… Just ask the 11 year old boy who killed his sister last week while playing with the gun… (I have a 3 y/o boy and guns and similar violent games are a NO NO for as long as we can avoid it.) Good project, though… Just wrap it in another package and present it differently.

  4. @sansan:

    Coil guns are a legitimate hacking abd engineering challenge. They are _not_ practical enough to be of any use for people with undesirable motives.

    In fact, airguns and improvised firearms are far easier to make and provide much more efficiency and power.

    Also, what people do in their own backyard/room without causing damage to other people and their possessions is their own damn business.

    Finally, it’s quite useless to whine on a hacking site about projectile weapons. Hint: quite a lot of people here don’t mind flying projectiles at high speeds, provided that experiments are done responsibly.

  5. @mp

    Yes, I have an aberration/phobia to harm, hurt and kill people or animals… Shouldn’t we all? hunting and violence is out of my principles and values. To you @mp, just happy hunting and hope your kids don’t get hurt…


    Agree with you. I remember that the first application I saw about that was AEG-Telefunken using high power SCRs to mold aluminum using a similar principle. I was astonished how awesome that worked, especially because aluminum was bent through a magnetic force! Similar in concept.

  6. @sansan. I don’t think anyone is going to be carrying this through airport security. And it may have a pistol grip, but that doesn’t mean it’s a scary dangerous weapon — power drills and hair dryers have pistol grips as well. It’s just a convenient shape.

  7. @sansan

    go cry somewhere where people actually give a shit about the fact that you hate guns. firearms are just a tool, like a hammer or chainsaw. people get killed with hammers and chainsaws all the time but somehow i doubt you are crying out about how talking about woodworking is some kind of subversive subliminal message promoting violence.

  8. “Why are guns so important to HackDay? I know people will argue that it is a toy. Try to explain this idea to an officer through airport security.”

    You could have any improvised electronic device with exposed wires and they would not allow it, even if it doesn’t look like a gun. I don’t think airport security is a good check on whether something should be considered a weapon or not.

  9. Anyway, to stay a little bit on topic:

    I could easily replicate this project using an Arduino (yes I’m a n00b), some sensors and a lcd display to display the results, but it would be more interesting to make the meter work like a “Chrony” (
    That way you don’t have to attach the meter to the coilgun, airgun etc. Also, projectiles of any practical size can be analyzed.

    Anyone here knows how the Chrony works exactly? It seems to operate with infrared leds on the top in a diffusor and IR phototransistors on the bottom. When a projectile passes the detectors, the amount of IR light received by the phototransistors is reduced momentarily. These reductions are interpreted as pulses. Then the speed of the projectile can be easily calculated.

  10. @gunner: there is a difference between a hammer and a gun. Sure, you can kill someone with either one, but a gun’s only purpose is to kill.

    That said, cool project! I don’t mind seeing it here at all.

  11. “Why are guns so important to HackDay? I know people will argue that it is a toy. Try to explain this idea to an officer through airport security.”

    I think this is a topic that should be asked directly to Hack-A-Day through the contact links. The comment threads are for constructive responses to the hack at hand and not for political agendas whatever they may be.

  12. @sansan

    Contrary to what you may see on TV, firearms are not even in the top 10 causes of death – not even in the US.

    If you do more research you’ll find that people mostly die from the results of poor diet, lack of exercise, communicable diseases, work related accidents, road accidents and so on till we get down to #11 on the list, suicides which account for 56.5% of all gun deaths in the US, the remainder of gun deaths being mostly the drug trade followed by law enforcement and military action. But taking away guns won’t stop suicides or crime. The suicide rate for women in China, Japan & South Korea is 3x the rate in the US which has easy access to firearms and 7x the rate in Israel which has mandatory firearms training.

    What if you have a child? Well, they’re more likely to die from a swimming pool or car accident.

    What about terrorists? Well, you’re more likely to be killed by your own government than by terrorists.

    Things like coil guns & rail guns help understand technology that led to maglev trains and may one day help us transport the resources of the entire solar system for the benefit of everyone.

  13. “a gun’s only purpose is to kill”

    I disagree. A guns main purpose is to defend and protect. 80% of people shot by a handgun survive. So if it’s only purpose were to kill, don’t you think it would be more effective? You look at the statistics and see the thousands killed every year by firearms. Why do you ignore the statistics that show the MILLIONS SAVED by firearms every year.

    Great hack. Sorry to go off topic.

  14. @guner

    Hey, red-neck punk: I see the type of trash you are by having to use foul language and how you express yourself. If you haven’t noticed, we are already in the 21st century, where you don’t need to hunt to survive, or need to protect yourself from the confederates or the government. Read what Jeff-o said. In any case, I agree with Bigalexe and others. Cool hack.

  15. @sansan
    “you don’t need to protect yourself from the government”

    some, such as the german jews, soviet dissenters, chinese under mau and slaves in te s. usa might disagree.

  16. on the weapons debate, you guys can just stop.

    These are obviously not being used as weapons, nor being mass produced. This gentleman is taking an artistic approach to a hobby construction. yes, his final result hurls a projectile. I don’t think he’ll be out shooting people with it defense or not. Relax.

  17. Amen Caleb:

    the whole purpose of this exercise was to get information, tweak an idea and make it better. the ability alter something is both far more productive AND makes it way to dangerous, at the same time, it deserves respect.

  18. “Hey, red-neck punk: I see the type of trash you are by having to use foul language and how you express yourself.”
    Oh no, i said shit! does that offend your delicate sensibilities?
    “If you haven’t noticed, we are already in the 21st century, where you don’t need to hunt to survive, or need to protect yourself from the confederates or the government.” need? maybe not, but if/when the shit hits the fan its going to be the people who cant hunt that are gonna be hurting. also see what MP said. I would rather be prepared for any eventuality than caught with my pants down.

  19. Agree with Calebkraft…. and to the red-neck punk, don’t worry. If the time comes where we need to go and hunt again and protect from the soviets and the whole paranoia, I am sure that other more important problems will be concerning us than running around with a weapon… good night.

  20. sansan- firearms are tools. You say that you don’t need to hunt to survive. While this may be true, it is sad. Believe me when I say I am not a vegetarian/ PETA person etc., but being able to be self-sufficient will always rank high in my book (I know you don’t care. yada yada. ) In the event that you do eat meat: you are a pathetic human being if you can not appreciate the animals that you eat, and could not bring yourself to take one, while letting others do the dirty work. There is more to killing an animal than pulling the trigger. The biggest reason firearms cause as much damage to innocent people as they do, is lack of education and paranoia, and compared to everything else I would say it’s just paranoia that gets everyone all excited.

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