Controlling a spud gun with an Arduino

We’re a long way from the Aquanet-powered plastic pipe spud guns of our youth. [smirpab] over on the SpudFiles forum posted a work in progress of an amazing replica AS50 sniper rifle he’s building. This pneumatic cannon goes above and beyond any air-powered rifle we’ve seen with an Arduino that is able to switch between automatic, semi-automatic, and burst modes with an LCD display and a rate of fire control.

The mechanics of [smirpab]‘s build are fairly normal for this level of pneumatic gun; it shoots 6mm plastic pellets from a smooth bore barrel with using air compressed to about 10 bar (145 psi). The electronics is where this project really shines, with an Arduino controlling the mode of fire (auto, semi-auto, and a 3-round burst), and the number of rounds per second adjustable with a pot.

A very cool project, and looking at the CAD renders of what [smirpab] completed project will look like, we can’t wait to see this build finished. As always, this build comes with the standard Hackaday “you’ll put your eye out, kid” warning. You can check out a video of [smirpab]‘s piston after the break, along with a demo of the Arduino-powered control circuit going through all three firing modes.

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Programming the XMEGA with an ISP

Atmel’s XMEGA series of microcontrollers are neat little pieces of hardware; with a very fast clock, a ton of IO, USB, and up to 8 UART ports, these neat little chips serve as a nice bridge between AVRs and PICs and the very powerful ARM chips coming out on the market. Unfortunately, the XMEGAs don’t use the extremely common ISP programming header found on just about every AVR dev board making them a bear to program. [Szu] over in Poland came up with a very easy way to program these chips, all while using the programming hardware you already have on hand.

[Szu]‘s build uses a few resistors and diodes to break out a USBASP connection to the XMEGA’s PDI interface. On the software side of things, [Szu] wrote an update to the USBASP firmware to allow it to program PDI devices, and also has a patch for AVRdude to allow uploading firmware from the command line.

A very cool build, and one that allows for very, very powerful devices that build on the AVR code you’ve already written.

Very inexpensive RF module tutorial

Let’s say you need a way to make a project wireless, but don’t have the scratch for a ZigBee or its ilk. You could use IR, but that has a limited range and can only work within a line of sight of the receiver. [Camilo] sent in a project (Spanish, translation) to connect two devices via a wireless serial connection. As a small bonus, his wireless setup is cheap enough to create a wireless network of dozens of sensors.

[Camilo] used the TLP434A transmitter/receiver combination to get his wireless project off the ground. These small devices only cost about $5, but being so inexpensive means the hardware designer needs to whip up their own communications protocol.

For a microcontroller, [Camilo] chose a Freescale MC9S08QC, a pleasant refrain from the AVR or PIC we normally see. After making a small board for his transmitter, [Camilo] had a very small remote control, able to send button presses or other data to a remote receiver.

After the break, you can see a short demo video [Camilo] posted of his wireless transmitter turning on an LED attached to his receiver. Unfortunately, this video was filmed with a potato, but all the schematics and code is on his web site for your perusal.

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Real time GPS decoding with software defined radio

In case the Realtek RTL2832u-based USB TV tuner dongle isn’t useful enough, the folks behind a project to get a software defined GPS receiver off the ground successfully plotted GPS data in real-time with this very inexpensive radio.

Previously, we’ve seen these dongles grab data from GPS satellites - useful if you’re building a GPS-based clock – but this build required hours of data collection to plot your location on a map.

The folks working on the GNSS-SDR project used an RTL2832 USB TV tuner and a Garmin active GPS antenna to track up to four GPS satellites in real-time and plot a location accurate to about 200 meters.

The Google Earth plot for this post shows the data collected by the GNSS-SDR team; the antenna was fixed at the red arrow for the entirety of the test, and the  yellow lines represent a change in the calculated location every 10 seconds. Amazing work, and only goes to show what this remarkable piece of hardware is capable of.