Easily Turn Your Raspberry Pi Into An FM Transmitter

June 15, 2014 by Rick Osgood 41 Comments

Have you ever wanted to be your own radio DJ? [Kevin] has made it easier than ever with his Raspberry Pi FM Transmitter program. The program is written in C. [Kevin] has made source code is available along with a compiled binary.

PIFM allows you to load up any audio file and specify a frequency to transmit. The program will then use PWM to modulate the audio sample through the Pi’s GPIO4 pin. [Kevin] claims that the RasPi alone will only transmit around a 10 cm distance. He says that making a simple antenna out of a jumper wire can increase the distance to around 100 meters. All you have to do is hook up the wire to the GPIO4 pin to drastically increase the range.

The legality of such a transmitter will vary from place to place, so be sure to check out your local regulations before you go transmitting audio on regulated frequencies. If this kind of thing is interesting to you, you may want to investigate ham radio. It’s not all Morse code and old fogies. Some people claim it’s a hacker’s paradise.

[via Reddit]

A Tweeting Litter Box

June 6, 2014 by Nick Conn 44 Comments

SmartLitterBox

How can you not be interested in a project that uses load cells, Bluetooth, a Raspberry Pi, and Twitter. Even for those of our readers without a cat, [Scott’s] tweeting litter box is worth the read.

Each aspect of this project can be re-purposed for almost any application. The inexpensive load cells, which available from eBay and other retailers, is used to sense when a cat is inside the litter box. Typically sensors like the load cell (that contain a strain gauge) this use a Wheatstone bridge, which is very important for maximizing the sensitivity of resistive sensor. The output then goes to a HX711, which is an ADC specifically built for load cells. A simple alternative would be using an instrumentation amplifier and the built-in ADC of the Arduino. Now, the magic happens. The weight reading is transmitted via an HC-06 Bluetooth module to a Raspberry Pi. Using a simple Perl script, the excreted weight, duration, and the cat’s resulting body weight is then tweeted!

Very nice work! This is a well thought out project that we could see being expanded to recognize the difference between multiple cats (or any other animal that goes inside).

The Game Boy Pocket Raspi Mod Puts All Others To Shame

June 5, 2014 by Brian Benchoff 45 Comments

There are hundreds – perhaps thousands – of builds out there on the Internet that put a Raspberry Pi in an enclosure with buttons meant solely for running emulators for old games. This one is unlike any other. Yes, it’s still basically a RetroPi emulator, but this Game Boy Pocket casemod goes beyond any remotely comparable build.

The Game Boy Pocket is incredibly small, but after sanding down the bosses on the inside of the case, gluing the battery door shut, and installing a bit of plastic over the cartridge slot, [WarriorRocker] was able to fit a Raspi inside. The buttons use the same PCB as the stock Game Boy, connected to a Teensy 2.0 board that simulates a USB keyboard.

With the two largest components taken care of, [Warrior] turned his attention to the sound, video and power. The display is a 2.5″ composite LCD that actually fits quite nicely behind the screen bezel. Audio is taken care of by a $3 audio amplifier, a new, smaller speaker, and a side-mounted pot stolen from the original Game Boy guts. There’s no chance on running this with the same 2xAAA cells the original Game Boy Pocket had, so [Warrior] somehow found space for a 2600mAh Li-Poly battery, a step-up regulator, and a charge circuit.

The result is a full-color RetroPi build capable of running for three hours before needing a recharge. All the classic Game Boy games are loaded onto the SD card along with select titles for other systems. The result is one of the best portabalized Raspi builds we’ve ever seen. Video below.

Continue reading “The Game Boy Pocket Raspi Mod Puts All Others To Shame” →

Raspberry Pi Coin Dozer Won’t Make You Rich

June 3, 2014 by Will Sweatman 13 Comments

Raspi in a coin dozer case

[SoggyBunz] lucked up and scored an Ultimate Raspberry Pi Bundle from Element 14. His idea was to use a Raspberry Pi to make a retro-mechanical arcade Coin Dozer game, and decided to build his first prototype inside a vacant Macintosh Plus shell.

The game is based on a Raspberry Pi running a small Python script. The Raspi operates a small servo that moves a piece of acrylic back and forth in a somewhat random fashion. The coins are inserted into slots cut into the Macintosh shell and eventually pile up. The moving acrylic lever pushes your winnings out of the machine and deposits them on whatever it’s sitting on, unlike this coin dispensing machine.

[SoggyBunz] concedes that the build is a bit rough and a servo is not the best choice of an actuator. But he aims to build a much improved version, and we can only hope he puts it on Hackaday.io and tips us in! Stick around after the break for a video of the Pi Dozer in action.

Continue reading “Raspberry Pi Coin Dozer Won’t Make You Rich” →

Controlling RC Toys With The Raspi

June 3, 2014 by Brian Benchoff 18 Comments

signal

An interesting trick you can do with a a fast CPU and a GPIO pin mapped directly to memory is an FM transmitter. Just toggle a pin on and off fast enough, and you have a crude and kludgy transmitter. [Brandon] saw a few builds that turned a Raspberry Pi into an FM radio transmitter and realized a lot of toy remote control cars use a frequency in the same range a Pi can transmit at. It’s not much of a leap to realize the Pi can control these remote control cars using only a length of wire attached to a GPIO pin.

The original hack that turned a Pi GPIO pin into an FM transmitter mapped a GPIO pin to memory, cycled through that memory at about 100 MHz, and added a fractional divider to slightly adjust the frequency, turning it into an FM transmitter. Cheap RC cars usually listen for radio signals at 27 and 49 MHz. It doesn’t take much to realize commanding RC cars with a Pi is possible.

The only problem with this idea is that most RC cars use pulse modulation. For an RC transmitter to send the command for ‘forward’, a synchronization pulse is sent, then a series of pulses and pauses. The frequency doesn’t change at all, something the originally FM code doesn’t do. [Brandon] realized that if he just moved the frequency up to something the RC car wasn’t listening to, that would register as a zero.

All that was left was to figure out the command codes for his RC truck. For this, [Brandon] decided brute force would be the best option. Armed with a script and a webcam, he cycled through all possible combinations until the webcam detected a moving truck. Subtlety brilliant, if you ask us. Of course more complex commands required an oscilloscope, but now [Brandon] has a git full of all the code to control a cheap RC car with a Pi.

RetroPie Portable Build Uses No Fancy Tools!

June 3, 2014 by James Hobson 19 Comments

retro pie portable

RetroPie Portable builds are great fun, but lots of them make use of expensive tools like 3D printers and laser cutters, which tends to dismay — [Kaushlesh] proves you don’t need any of that!

To build his unit he’s using a Raspberry Pi, a USB controller, a 6 x 4″ project box, a cheap LCD screen, a hot glue gun, and various electrical components — you will still need some soldering skill to complete this project!

By modifying the case he assembled the control boards by taking apart the USB controller. Protoboard made for an easy way to mount his new buttons, with it simply hot glued in place. Quite a bit of soldering later and everything is connected. He notes you’d better make sure everything works as you go otherwise it will be hard to find out what’s wrong when it is assembled!

Future upgrades include a rechargeable li-ion pack and built in speakers (he’s currently using headphones). Take a look after the break!

Continue reading “RetroPie Portable Build Uses No Fancy Tools!” →

Original NES Guts Upgraded With RetroPie

June 1, 2014 by Rick Osgood 21 Comments

If you have an old broken NES lying around and have no idea what to do with it, you may want to check out [snoius’s] latest project. He replaced the guts of his old NES with a Raspberry Pi. [snoius] started out by removing most of the electronics from his original NES to make room for the Pi. He left the original control panel board so he would be able to use the original power button and power LED. The NES power switch is an on/off toggle switch. [snoius] decided to just route the 5V USB power input directly through this switch. The result is a hard power switch for the tiny computer. The original power LED is wired up to the Pi’s 3.3V GPIO header through a 330 ohm resistor. Now when the Pi has power, the LED lights up.

The next step was controllers. It looks like [snoius] is using some USB SNES controller clones. He wanted to use the original NES controller ports but obviously the NES did not utilize USB. [snoius] used a saw to cut the backs off of the controller ports, leaving a flat surface. He then used a utility knife to carve out a hole in the shape of a female USB port. He mounted some ports in place and then wired the inside up to some short USB cables with male ends. These were plugged into a USB hub that is hidden inside of the NES case.

The Pi is also hooked up to a short HDMI cable and a short power cable. The loose ends of the cables are mounted to a small block of wood. Notches are cut out of the wood to better fit the cable ends. The rear of the NES has two holes cut out where the original connectors used to be in order to accommodate the new connectors.

With all of the hardware taken care of, [snoius] still needed a way to actually play his games. That’s where RetroPie saved the day. RetroPie is a Linux distribution for the Raspberry Pi that is specifically created to make it easy to play old video games. It includes emulators for many old systems including NES, SNES, SEGA Genesis, Gameboy, etc. [snoius] installed RetroPie onto an 8GB SD card and copied over all of the ROMs he could find. The end result is what appears to be an original NES at a glance, but is in fact multiple retro gaming systems in one. It also contains hundreds of video games in on board memory instead of requiring a large library of physical cartridges.

[via reddit]