Tennis Ball Launcher Has Puppies Running The 100m Dash

June 14, 2014 by 17 Comments

Launching Tennis Balls with Ease

[Brian] from 24 Hour Engineer has a friend with arthritis who can’t easily play ball with his new puppy — so [Brian] stepped in and built him this awesome tennis ball launcher.

You see, most tennis ball launchers require a solid flick of the wrist, and since just plain old throwing it is out of the question too, [Brian] had to make him something powerful and easy to use. After sketching out some designs he came up with the basic concept that eventually became what is pictured above.

The frame is made of 2″ PVC pipe, which serves two purposes, support, and safety. The bungee cord launching system is actually contained within the pipe, keeping it out of the way, and free from catching on anything during firing. A pair of pulleys mounted at the cord opening ensure the cord doesn’t wear out.

What we really like is the trigger mechanism [Brian] made out of some carefully cut wood,  a steel corner brace and a few nuts and bolts. It’s a simple mechanism that provides leverage and an easy way to release the bungee cord.  Continue reading “Tennis Ball Launcher Has Puppies Running The 100m Dash” →

High Voltage Monitor Power Supply Conversion

Repurpose An Old CRT Computer Monitor As A High Voltage Science Project Power Supply

June 14, 2014 by 17 Comments

Finally somebody has found a good use for all those old CRT computer monitors finding their way to the landfills. [Steven Dufresne] from Rimstar.org steps us through a very simple conversion of a CRT computer monitor into a high-voltage power supply. Sure you can make a few small sparks but this conversion is also useful for many science projects. [Steve] uses the monitor power supply to demonstrate powering an ionocraft in his video, a classic science experiment using high voltage.

The conversion is just as simple as you would think. You need to safely discharge the TV tube, cut the cup off the high voltage anode cable and reroute it to a mounting bracket outside the monitor. The system needs to be earth grounded so [Steve] connects up a couple of ground cables. One ground cable for the project and one for a safety discharge rod. It’s really that simple and once wired up to a science project you have 25kV volts at your disposal by simply turning on the monitor. You don’t want to produce a lot of large sparks with this conversion because it will destroy the parts inside the monitor. The 240K Ohm 2 watt resistor [Steve] added will help keep those discharges to a minimum and protect the monitor from being destroyed.

Yes this is dangerous but when you’re working with high-voltage science experiments danger is something you deal with correctly. This isn’t the safest way to get high-voltage but if you have to hack something together for a project this will get you there and [Steve] is quite cautious including warning people of the dangers and how to safely discharge your experiment and the power supply after every use. This isn’t the first high-voltage power supply that [Steve] has constructed; we featured his home-built 30kV power supply in the past, which is a more conventional way to build a HV power supply using a doubler or tripler circuit. Join us after the break to watch the video.

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The Worst E-Reader Ever

June 14, 2014 by 29 Comments

oled

Over on the Projects site, [Jaromir] has created a tiny device with an OLED display, three buttons, and a USB port for storing text files, be it for saving a shopping list, a cheat sheet, or the most unusable e-reader ever made.

The front of the device is simply a 96×32 pixel OLED and three buttons for ‘up’, ‘down’, and ‘open/close’. The reverse side is where the magic happens with a PIC24 microcontroller that sets up a file system on the chip, allowing [Jaromir] to write 64kB of data on what is actually a Flash drive with a pitiful capacity. Text files are viewable on the OLED, with the video below showing the front page of Wikipedia being displayed in a glorious 16×4 text mode.

It’s not a very useful device by any means, but for some reason it’s garnered a lot of skulls and followers over on Hackaday Projects. In response to that, [Jaromir] is working on version two with a new PCB and a design for a 3D printed case. Not bad for what [Jaromir] himself describes as worse than just about any phone or tablet.

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The first Radar Arduino Shield

The First Arduino Radar Shield

June 14, 2014 by 16 Comments

The very first fully operational radar Arduino shield was recently demonstrated at Bay area Maker Faire. It was built by [Daniel] and [David], both undergrads at UC Davis.

Many have talked about doing this, some have even prototyped pieces of it, but these undergrad college students pulled it off. This is the result from Prof. ‘Leo’ Liu’s full-semester senior design course based on the MIT Coffee Can radar short course, which has been going on for 2 years now. Next year this course will have 30 students, showing the world the interest and market-for project based learning.

Check out the high res ranging demo, where a wider band chirp was used to amazing results. Video below.
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Home Made Miter Saw Is Not Completely Dangerous

June 14, 2014 by 43 Comments

Home Made Miter Saw

If the term ‘home made miter saw’ instantly instills frightening images of severed limbs into your head, you’re not alone. A quick internet search will yield some pretty hokey tool builds, we’ve even featured a few here on hackaday. This saw is different. [Pekka] made a pretty cool saw for cutting very accurate angles in wood.

This saw was purpose built with one goal in mind: cutting wood that will be glued together for use in segmented turning. Segmented turning is shaping a piece of wood stock that is composed of many different types of wood. This results in a very visually interesting product.

Home Made Miter SawMost of the saw is made from plywood. The hinge and supports for the arbor are beefy off-the-shelf pillow blocks. A 3-phase motor with speed control transmits power to the arbor via a belt. Belt tension is adjusted by sliding the motor further back along the motor mount base. [Pekka] took care so that the entire pivoting assembly was nearly balanced adding to the ease of use.Typical miter saws rotate the blade to achieve different angles of cuts. This design rotates the saw fence.

For safety there are a pair of polycarbonate blade guards and a micro switch on the handle that won’t let the saw start unless it is depressed. The micro switch has a secondary function also, when let go it applies an electronic brake to the motor so that the spinning blade does not touch the work piece when lifting the blade back up.

An ARM-Based DSP Modelling Synth

June 14, 2014 by 42 Comments

synth

The great analog synths of Moog, Oberheim, Sequential Circuits, and more modern version from Doepfer are renouned for their sound, the sheer majesty of a rack full of knobs and plugs, and of course the price. Analog synths are simply expensive to build, and given that aficionados even scoff at digitally controlled oscillators, require a lot of engineering to build. [Jan]’s DSP-G1 isn’t like those analog synths – it uses microcontrollers and DSP to generate its bleeps and boops. It is, however, extremely cheap and sounds close enough to the real thing that it could easily find a home between a few euroracks and CV keyboards.

plugThe heart of the DSP-G1 is a micro from NXP modeling an analog synthesizer with 15 digitally controlled oscillators with Sine, Triangle, Pulse and Saw outputs, a low frequency oscillator, two envelope filters, and a low pass filter, or about the same accouterments you would find in a MiniMoog or other vintage synth from the 70s. Since this is basically a synth on an NXP LPC-810, [Jan] has packaged it in something akin to a MIDI to 3.5mm cable adapter: Plug a MIDI keyboard into one end, an amp into the other, and you have a synth smaller than the MIDI Vampire, an already impossibly small music creation tool.

[Jan] has a few more versions of his little DSP device with varying amounts of knobs available on his indiegogo campaign. The DSP-Gplug is the star of the show, though, provided you already have a MIDI keyboard with a few knobs for the required CC messages. Videos and sound demos below.

Continue reading “An ARM-Based DSP Modelling Synth” →

Do You Have Any Idea How Fast Your Blender Was Going?

June 13, 2014 by 23 Comments

blenderSpeed Some people really love their smoothies. We mean really, really, love smoothies and everything about making them, especially the blenders. [Adam] is a big fan of blenders, and wanted to verify that his Vitamix blenders ran as fast as the manufacturer claimed. So he built not one, but two speed measuring setups. Scientific blender measurement method requires one to cross check their results to be sure, right?

Measuring the speed of a blender is all about the RPM. Appropriately, [Adam’s] first measurement tool was an LED based stroboscope. Stroboscopes have been around for hundreds of years, and are a great way to measure how fast an object is rotating. Just adjust the speed of a flashing light until the rotating object appears frozen. The number of blinks per second is then equal to the Rotations Per Second (RPS) of the object being measured.Multiply by 60 seconds, and you’ve got RPM. [Adam] used an Arduino as the brains behind his stroboscope. He wired a dial up on his breadboard, and used it to adjust the flash rate of an LED. Since this was a quick hack, [Adam] skipped the display and just used the Arduino’s USB output to display speed measurements on his laptop.

There are possibilities for error with stroboscopes. [Adam] discovered that if the stroboscope was flashing at a multiple of the blade’s rotation speed, the blades would appear frozen, and he’d get an erroneous RPM value. Thankfully, [Adam’s] Vitamix had asymmetric blades, which made the test a bit easier. He calculated his blades to be spinning at 380 RPS, or 23,000 RPM. Not satisfied with his results, [Adam] brought out Audacity, and ran a spectral analysis of the blender in operation. He found a peak at 378Hz, which was pretty darn close to his previous measurement. Since the blender has a 4 inch blade this all works out to a blade tip speed right around the claimed value of 270 MPH. We’re glad [Adam] found an answer to his blender questions, but our personal favorite blender hack still has to be the V8 blender created by the Top Gear crew.   [via HackerNews]