Crazy slingshot guy at it again with a 220 lb steel ball cannon


Good old [Jörg Sprave].

That guy just doesn’t quit building insane slingshots. If he’s not honing his machete slinging skills in preparation for the zombie apocalypse, he’s blowing out car windows with giant steel balls.

The huge cannon you see above is modeled off a small slingshot he made a while back, which fired 8mm steel bearings. In its larger form, the slingshot is said to be ten times the size of it’s smaller brother, firing 80mm steel balls with incredible force. In the video below, [Jörg] and his friends cart the slingshot out to a huge empty field where they run it through its paces on several different objects. Their first shot flies about 220 yards into a high tension tower, after which the boys aim their sights on an old car.

The power with which the slingshot fires is definitely impressive. With a few well-placed shots, the car is pretty much done for.

Now that we’ve seen [Jörg] fire off saw blades, machetes, and giant ball bearings, we can’t wait to see what comes next!

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Engine Hacks: Adding fuel injection to a riding lawnmower

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Are you tired of fiddling with the engines on your lawn equipment every spring, trying to get them to run again? [jhark] was and decided to do something about it by converting his riding lawnmower over to fuel injection. After stealing a fuel injector from his van and bolting it onto the mower’s carburetor, he sprinkled in a dash of Arduino magic. With a small amount of code tweaking he was ready to roll mow. You can find a schematic and his code if you follow the forum link to the second page.

For more fuel injection goodness, check out this project where [Steve] upgrades his Austin Healey to use the fuel injection system from a General Motors vehicle. This build log is pretty comprehensive and shows each element in the system, describes what it does, and shows where it should go. If you are a car nut, this is definitely one to check out.

Finally, if you are looking to really dig into the nuts and bolts of automotive fuel injection, take a look at the Megasquirt fuel injection computer system that allows you to finely tune things to your specific car and model.

Monitoring water levels with a Parallax Ping sensor


When you need a mechanism to detect the water level within a container or tank, you have several different options. Most people opt for a simple float or probe that sits in the water, while others use optics to sense when the water is reaching an undesired level.

This device built by [Danilo Abbasciano] uses a Parallax Ping sensor instead. If the sensor is placed at the top of a well, cistern, or other water container, it can accurately calculate the height and volume of the fluid inside. This is done by using the Ping’s readings in conjunction with a few values already known to the user, namely the dimensions of the container.

In his implementation, the readings are relayed to a simple LCD panel for easy viewing, and a small piezo speaker is used to sound an alarm when the water level reaches a predefined threshold. This sort of measuring device can be quite useful in situations where a contact-based sensor would be subject to chemicals and corrosion, or where contamination is a concern.

Speaker-mounted WAV player for street performances

This naked speaker is the basis for [MaoMakMaa's] newest project called the Wavedrone. He plans on using the autonomous and cable-less device during street performances. You can hear the effect of some stretched jazz cords being played on it in the video clip after the break. The sound is kind of an ethereal background noise that observers might not immediately realize is there.

You can see the 9V battery which serves as the power source clinging to the frame of the speaker. A 7805 linear regulator tames that battery and feeds the two IC’s on the circuit board seen to the right. The ATtiny85 is reading music from an SD card and playing it back in mono (obviously) with the help of an LM386 audio amplifier chip. The trimpots that go into the high pass and low pass filters in between the microcontroller and amplifier allow for a bit of sound manipulation, but we’re more impressed with the quality of the sound this is getting when properly trimmed.

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Chumby controlled mechanum wheel robot

[Madox] gutted an Insignia Infocast to use with this robot. Insignia is Best Buy’s house brand and they partnered with Chumby to make their Infocast line. If you can find a used or clearance model it’s a great way to get yourself and embedded Linux board for a project like this one.

The body and wheels are 3D printed, with design files available at [Madox's] Thingiverse page. The mechanum wheels work amazingly well, using seven bearings each for smooth operation. The body itself includes a holder for two groups of batteries. One of those battery packs powers the Chumby board while the other is used to power the four servo motors responsible for locomotion. To simplify the electronics [Madox] chose to use a USB servo drive which only set him back about $20.

We’re not sure what the USB dongle on top of the robot is used for. We’d guess it’s a WiFi adapter, since the machine sets up its own access point to act as a controller. But we thought Chumby boards had WiFi built-in. At any rate, check out the video after the break where you can see an Android phone driving the little bugger. There’s a flaw in the code that prevents side-to-side movement, it gets fixed after a video break at about 2:15 and everything is peachy after that.

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[Easton's] animatronic hand gets 3D printed upgrade

[Easton] as been working with [Jeremy Blum] to come up with the newest version of his animatronic hand. You may remember seeing [Easton's] first animatronic hand, with which he won his regional science fair and made a trip to nations. Since then he’s been working on improvements, and with access to [Jeremy's] Makerbot he harnessed the power of open source design to make his own printed hand, extending a different Thingiverse project.

He’s still using the original sensor glove as a controller. It sends commands to the Arduino controlling the arm via an Xbee module. From there, five servos inside a fiberglass forearm move each finger and the thumb. The video clip after the break gives [Easton] a chance to show off all of the new design features, and finishes with a demonstration of the hand grasping different objects. We had a chance to chat with him briefly. He’s got big goals for himself, aiming to design a prosthetic arm for under $1000. That’s not a career goal… he’d like to get it done this year.

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Got an iLight?

[KaRMaN] sent us a piece from his blog on what to do with a busted iPhone (google translate). As many iPhone owners have found out, it does not take that much of a fall to render your shiny hand-held command center into a pile of shattered glass. Replacement parts and insurance are available so life goes on, but what else can you do?

One thing you could do if your screen split apart like [KaRMaN]‘s is remove the white LED back light strip from the device and reuse it. Once he removed the LED he had to repair a couple of traces but that is no big deal. Then the strip is probed to see how the individual LED’s are situated, in this case is 6 in series. The strip is hooked up to a 12v power source and now you have a small, but bright light for some midnight hacking.