An Arduino Power Inverter

June 21, 2013 by Brian Benchoff 32 Comments

If you’ve got a few solar panels lying around, or even if you want some 120/230 V AC power from a few 12 Volt batteries, you’ll need a power inverter. Sure, you can drop on down to any big box store and pick one of these up, or you can be like [Michael] and build your own (Danish, translation).

[Michael] found himself in the possession of a few halogen light transformers and decided to make use of them by building a DC to AC power inverter. The inverter is fairly simple – just the transformer, a few MOSFETS, and an ATMega0168 for software control that includes a ‘soft start’ feature that prevents power surges on startup.

The circuit is simple enough to etch at home, although a soldermask and a nice insulated enclosure would probably be ideal for this application.

Guitarduino Show And Tell

June 14, 2013 by Mike Szczys 13 Comments

guitarduino-show-and-tell

[Igor Stolarsky] plays in a band called 3’s & Sevens. We’d say he is the Guitarist but since he’s playing this hacked axe we probably should call him the band’s Guitarduinist. Scroll down and listen to the quick demo clip of what he can do with the hardware add-ons, then check out his video explanation of the hardware.

There are several added inputs attached to the guitar itself. The most obvious is the set of colored buttons which are a shield riding on the Arduino board itself. This attaches to his computer via a USB cable where it is controlling his MaxMSP patches. They’re out of the way and act as something of a sample looper which he can then play along with. But look at the guitar body under his strumming hand and you’ll also see a few grey patches. These, along with one long strip on the back of the neck, are pressure sensors which he actuates while playing. The result is a level of seamless integration we don’t remember seeing before. Now he just needs to move the prototype to a wireless system and he’ll be set.

If you don’t have the skills to shred like [Igor] perhaps an automatic chording device will give you a leg up.

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Loading Atari Games From An SD Card

June 12, 2013 by Brian Benchoff 16 Comments

Atari

They’re not a 2600, but the Atari 400, 800 and 1200 are awesome computers in their own right. With only BASIC built in to the ROM, they’re not especially useful or fun, as [Jeroen] found out when he acquired an 800 with a broken tape drive. There are options that allow you to load emulator files from a PC, but [Jeroen] wanted something more compact. He came up with a way to load games and apps off an SD card using a simple microcontroller.

The 400, 800, and 1200 each have a port that allows the computer to talk to printers, modems, disk drives, and load games. There are already a few circuits around that connect the SIO port to a computer so games can be loaded, but [Jeroen] wanted a more compact and portable solution for his 800.

What he came up with is actually pretty simple; just an Arduino, SD card, and an LCD display that allows him to browse the directory on the SD card and load it into the 800’s memory.

A lot of folks over on the Atariage forums are really impressed with [Jeroen]’s work, and would like to get their hands on one of these boards themselves. The project isn’t done just yet – [Jeroen] still needs to make a case for his device – but hopefully he’ll be spinning a few boards up in the coming months.

You can see a pair of videos of the device in action below.

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Giving An RC Tank A Fire Control Computer

June 11, 2013 by Brian Benchoff 29 Comments

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

June 9, 2013 by Mike Szczys 50 Comments

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

June 4, 2013 by Mike Szczys 14 Comments

aquarium-auto-doser

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

June 3, 2013 by Mike Szczys 8 Comments

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.