Propeller and machine gun timing

[Matt] was looking for a challenge. Inspired by the machine gun setups on World War I planes he wanted to make a gun that can shoot between the blades of a spinning propeller. The original guns used an interrupter gear that synchronized machine gun firing with the engine mechanically. [Matt] set out to do this using a microcontroller.

To make this work there are two important pieces of information; how fast is the propeller spinning right now, and how long does it take for the pellet to pass the blade? [Matt] used an oscilloscope and some infrared sensors to establish the firing delay at about 20-22ms. Another sensor shows the propeller is spinning at 500 RPMs, with some simple calculations showing that there is indeed a big enough window of time to fire between the blades. After testing with a visible LED and then building out the rest of the circuitry he accomplished his goal. He even added a test function that purposely hits the blades just to see how accurate the system was. We hope this shows up in a Red Baron RC replica, or other flying arsenal.

[via Hacked Gadgets]

Cheap(er) biometric gun safe

[Greg] sent in his biometric pistol safe lock. He keeps his guide light on details so not every Joe can crack the system (there is a thread to sift through if you really wanted to), but the idea runs fairly simple anyway. [Greg] took an old garage door opening fingerprint scanner and wired it into a half broken keypad based pistol safe. While he did have some issues finding a signal that only fired when the correct fingerprint is scanned, a little magic with a CMOS HEX inverter fixed that problem quick.

This does bring one question to our minds, are fingerprint scanners as easy to crack as fingerprint readers?

You’ll shoot your eye out, another coilgun

All we needed to read was 4x 3900uF capacitor bank to know we had yet another decently sized homemade coilgun on our hands. And for the math buffs, that equates out to 1.25kJ of potential energy (efficiency kills it down to 37j of kinetic, but large numbers are more fun) which is more than enough to break skin; of course we recommend you just shoot old electronics rather than friends. On the more technical side, sure its only a single stage for now and we’ve seen some slightly more impressive triple stage guns, but it may just be more beautiful than our previously featured coil pistol. You guys be the judge. Catch a complete video after the jump of the internals and build process, skip ahead to 2:40 for the destruction.

[via TheDailyWh.at]

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Live fire Half-life

We don’t know how we missed this when it first came out, but there is a hack out there that combines a .22 caliber pistol with the video game Half-life. Simple is best and that motto is in use here. A wall was built down range to use as a projection screen. Accelerometers mounted on the drywall report vibration data from the bullet strike which is used to triangulate its location. This targeting data is then sent to the game interface.

As you can see in the video after the break this works like a charm. The [Waterloo Labs] personnel that developed this are also responsible for that iPhone controlled car. The antics we witnessed in that project carry over to this one as they illustrate using the setup to play Half-life with a couple of shovels at 2:12 into the clip. [Read more...]

Nerf sentry turret

With exams behind him [Adam Greig] had time to make a Nerf sentry gun. It’s actually quite easy to pull everything together. He’s got a netbook running Motion, an open source motion sensing program for use with a webcam. When movement is detected an Arduino, connected via a USB cable, actuates a servo to pull the trigger of the gun. The turret itself has seen a battery upgrade that increases the firing speed. It’s fun to see hardware prototyping done with a few pencils and a fist full of cable ties. Check it out after the break.

This particular toy, the Nerf N-Strike Vulcan, has become quite a popular starting point for turrent projects. We’ve seen one that uses a motorized base, and another that was part of a final project at Cornell.

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Student Soaker, wireless water gun

As far as pranks go, [Austin Shaf's] wireless hidden water gun is a real treat. The video above goes over a brief explanation and shows the setup in action. The prankster holds onto a wireless AVR remote, and when the unsuspecting victim walks by, he activates a second AVR controlling a pump; spraying water everywhere.

While most of us are out of school by now, the project would still be a fun office or perhaps street prank. If you’re one for registering, schematics and source code can be found at AVRFreaks. Alternatively, check after the jump for a copy of both.

Related: Office Pranks, and Water Guns.

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Pressurized PVC water gun

Hackaday’s [Caleb Kraft] has branded today “kiddie d-day” after seeing this PVC water gun follow close on the heals of the LEGO sniper rifle. This is a great summer project if you don’t mind letting the kids use the quick connect on your air compressor. It’s really just a ‘T’ made of PVC with two valves for air and water management and a soda bottle on the third leg as a reservoir. In the short clip after the break you can see that you don’t get a lot of shooting time out of each charge compared to the DIY Super Soaker, but this build is also a lot less complicated.

[Read more...]