Giving An RC Tank A Fire Control Computer

tank

[Vincent] plays around with remote control tanks, and even though his current model is a WWII-era armor piece, he’d still like modern accoutrements such as a fire control computer and laser sighting for his main gun. His latest project did just that (French, Google translation) with the help of an Arduino, a few modifications to the receiver, and an IR rangefinder.

The stock RC tank includes servos to move the turret and the requisite electronics to fire an Airsoft gun. The precision of the mechanical movements inside the turret weren’t very precise, though, so [Vincent] had to gear down the servos to turn large movements into slight adjustments. After that, he installed an IR rangefinder and laser diode onto the barrel that allowed the gun to sight a target and read its distance.

After some experimentation with the rangefinder and laser, [Vincent] plotted data from firing a few BBs at a whole bunch of distances and targets. The graph came out fairly linear, and after plugging this into a graphing calculator, he was able to find an equation that took into account the distance and angle so the Arduino-powered fire control computer would hit its mark.

The accuracy of the gun is very impressive, all things considered. [Vincent] is able to accurately fire BBs downrange and hit an 8×12 cm target at five meters. You can check out that action below.

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Echolocation Pinpoints Where A Gunshot Came From

echolocating-gunshots

[Kripthor] suspected that hunters were getting too near his house. When thinking of a way to quantify this belief he set out to build a triangulation system based on the sound of gunshots. The theory behind it is acoustic location, which is a specialized type echolocation.

The most common example of echolocation is in Bats, who emit ultrasonic noise and listen for its return (echo) to judge the location of objects. [Kripthor] doesn’t need to generate the sound himself, he just needs to pick it up at different points. The time difference from the three samples can be used to triangulate coordinates as seen in the image above.

He first tried using a PC sound card to collect the samples. The stereo input only provides two channels so he tinkered around with a 555-based multiplexing circuit to sample from three. The circuit noise created was just too great so he transitioned to using an Arduino. The ADC samples from each microphone via an NPN transistor which is used as a simple amplifier.

This brings to mind a homebrew sonar hack from way back.

Automated Aquarium Fertilizer Doser

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If you are using live plants in your aquarium you must remember to fertilize them at regular intervals. Being a bit forgetful, [Deven] automated the process by building this auto-doser.

There are three different chemicals which are dispensed by the system. They are stored in the drink bottles seen above. Each has a plastic tube which runs up to the dosing motors mounted on the black box. [Deven] sourced the motors from eBay. They are designed for this type of application.

Inside the black box is the Arduino that handles timing and switches the motors. The control circuitry is protected using one MOSFET for each. To keep the fish safe the outflow is directed right into the aquarium pump so that the concentrated chemicals are quickly dispersed through the entire tank.

Now that he’s made it this far he might as well add the ability to feed the fish and control the lighting.

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Quick And Dirty Touch-sensitive Keyboard Project

quick-dirty-touch-sensitive-keyboard

You don’t have to have high-quality parts to play around with electronics and here’s a great example. [Vishal] used junk to play around with CapSense, the touch sensitive Arduino library. What he ended up with is this touch-based piano keyboard.

We’ve featured the CapSense library in the past, but even that example uses a very meticulously crafted test rig of foil tape, protoboard, and some resistors. If you still haven’t given it a try follow this example of using aluminum foil, electrical tape, and a cardboard box.

[Vishal] just sandwiched the end of jumper wire between two pieces of foil to make each ‘key’. We believe the other end of the wire is soldered to the bias resistors where they connect to a couple of pin headers. The headers were hot-glued in place through holes in the bottom of the box, making the entire rig simple to plug into the Arduino board driving it. After adding in a small speaker and flashing the code he’s finished. It certainly makes for a short afternoon project which you won’t feel bad about taking apart later since you didn’t sink a ton of time or resources into the build.

Benchmarking USB Transfer Speeds

boards

[Paul Stoffregen], creator of the Teensy series of microcontroller dev boards, noticed a lot of project driving huge LED arrays recently and decided to look into how fast microcontroller dev boards can receive data from a computer. More bits per second means more glowey LEDs, of course, so his benchmarking efforts are sure to be a hit with anyone planning some large-scale microcontroller projects.

The microcontrollers [Paul] tested included the Teensy 2.0, Teensy 3.0, the Leonardo and Due Arduinos, and the Fubarino Mini and Leaflabs Maple. These were tested in Linux ( Ubuntu 12.04 live CD ), OSX Lion, and Windows 7, all running on a 2012 MacBook Pro. When not considering the Teensy 2.0 and 3.0, the results of the tests were what you would expect: faster devices were able to receive more bytes per second.  When the Teensys were thrown into the mix, though, the results changed drastically. The Teensy 2.0, with the same microcontroller as the Arduino Leonardo, was able to outperform every board except for the Teensy 3.0.

[Paul] also took the effort to benchmark the different operating systems he used. Bottom line, if you’re transferring a lot of bytes at once, it really doesn’t matter which OS you’re using. For transferring small amounts of data, you may want to go with OS X. Windows is terrible for transferring single bytes; at one byte per transfer, Windows only manages 4kBps. With the same task, Linux and OS X manage about 53 and 860 (!) kBps, respectively.

So there you go. If you’re building a huge LED array, use a Teensy 3.0 with a MacBook. Of course [Paul] made all the code for his benchmarks open source, so feel free to replicate this experiment.

Arduino Particle Light Box Generates Animations From Sound

arduino-particle-display

Simple tools used well can produce fantastic results. The hardware which [Gilad] uses in this project is the definition of common. We’d bet you have most if not all of them on hand right now. But the end product is a light box which seems to dance and twirl with every sound in the room. You should go watch the demo video before reading the bill of materials so that the simplicity doesn’t spoil it for you.

A wooden craft box serves as the enclosure. Inside you’ll find an Arduino board, microphone, and an 8×8 RGB module. The front cover of the project box diffuses the light using a sheet of tracing paper on a frame of foam board. It’s the code that brings everything together. He wrote his own particle system library to generate interesting animations.

If you don’t have a project box on hand this might work with an extra-deep picture frame.
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Moostar — Fortune Telling Moose Knock-off Of Zoltar

zoltare-the-fortune-telling-moose

Meet Moostar, the fortune-telling Moose inspired by Zoltar. You remember Zoltar, the coin operated fortune-teller who made [Tom Hanks] a rich movie star? Maybe you didn’t see that flick, but [Sketchsk3tch] did and he pulled this show piece together for a company-wide conference with relative ease.

If you’re good at choosing parts for your projects it makes things a lot simpler. He started with a singing Christmas moose, a mini plasma ball to act as the crystal ball, and somehow came across a collector’s basketball case which was the perfect size for the enclosure.

The electronics also came together remarkably well. He uses a thermal printer to spit out the fortunes — which are actually security tips for employees since that’s the dcpartment he works in. The coin acceptor is a Sparkfun part and he tried two ready made solutions to make the moose talk. The first is seen below and uses pre-recorded messages played by an Arduino Wave shield. This was improved upon by using an EMIC2 text-to-speech module that really opens up the moose’s range of chatter.

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