When the Regency TR-1 transistor radio came out onto the market in the 1950s, it was hailed as a modern marvel of microelectronics. With only four transistors and a handful of other components, the TR-1 was a wonder of modern engineering. [Sprite_tm] may have those old-timers beat, though. He built an FM transmitter with the lowest parts count of any transmitter ever.

Like most of [Sprite_tm]‘s builds, it’s an unimaginably clever piece of work. [Sprite] overclocked the internal RC oscillator of an ATtiny45 to 24 MHz. After realizing the PLL running at four times the frequency of the oscillator was right in the middle of the FM band, he set about designing a tiny FM transmitter.

[Sprite_tm] remembered his work on MONOTONE and made a short song for hit ATtiny. The firmware for the build takes the notes from his song and varies the 96 MHz PLL frequency a tiny bit, thereby serving as a tiny FM transmitter.

Does it work? Well, if you want to compare it to a Mister Microphone, the range is incredibly limited. That being said it works. It’s an FM transmitter built out of a microcontroller and a battery, and that’s very impressive. Check out [Sprite_tm]‘s demo after the break.

[form], a new user on the Hack a Day forums, was thinking, “what Christmas present i can send a friend, that would be really annoying?” We think he really hit it out of the park with this one. It’s a modified computer speaker that will play “explicit” audio until the power button is pressed 200 times and the light sensor is covered. When this present is unwrapped, the room will fill with sounds not suitable for children, the elderly, or those with heart conditions.

The build is based around an old powered computer speaker. Six Li-ion batteries from an old laptop provide the power, and a very simple circuit pulls sound off an SD card with the help of an ATtiny45.

The schematic for the build looks easy enough, and like a good builder, [form] included the source and HEX files. Sadly (or thankfully), there is no video of the gag gift in action; probably a good thing, because this seems like a great way to lose a friend.

[Eberhard] wanted his own reflow oven but didn’t really want to mess around with the internals that control the heating element. He put his microcontroller programming experience to work and came up with an add-on module that controls the oven by switching the mains power.

The image above shows a board in the midst of the reflow process. If you’re not familiar, solder paste usually comes with a recommended heat curve for properly melting the slurry. [Eberhard] managed to fit three of these temperature profiles into his firmware.

The ATtiny45 which makes up the controller samples oven temperature via the thermistor seen next to the board. A PID algorithm is used to calculate when to switch mains power on and off via a relay. One button and one LED make up the controller’s user interface for scrolling through the three preprogrammed temperature profiles.

It looks like it works great, see for yourself in the clip after the break.

[Fernando] sent in a tangential project update that uses an ATtiny45 to play Pong on his television. Last time we looked in on his work he had just finished getting the eight-pin chip to display a big number on the TV via the VGA port. This expands on the idea while he continues to wait for parts.

Right now the chip plays against itself, but he’s got one input pin left and we’d love to see a button added for a simple one-player game. We’re thinking the paddle would always be moving in one direction or the other, with a click of the button to reverse that direction. The part that he’s waiting for is a Bluetooth module, which we’d love to see used for 2-player games via a pair of Wiimotes (we’re just wishing at this point and don’t know if that would even be possible). The end goal for the hardware is a Bluetooth connected scoreboard for Android devices.

The code is written in Assembly, and we found it relatively easy to follow what [Fernando] is doing with the game logic. On the graphics side of things he gets away with a 120×96 resolution because Pong is supposed to look pixelated. We love the result, which you can see for yourself after the break.

Servo8bit is a library for AVR microcontrollers that allows you to drive servo motors without the need for a 16-bit timer. Obviously, this is quite useful for smaller chips that only have 8-bit timers and it is specifically targeted at the ATtiny45 and ATtiny85 microcontrollers. The library offers 256 steps of resolution, and can drive up to five servos at one time. Servo control pulses can be generated between 512 and 2560 microseconds and if you don’t mind increasing the time between these pulses [Liya] says it would be possible to increase the 5-servo limit.

The library is quite easy to use, but in its current state it would take just a bit of work to port to another device. It’s been written for an 8 Mhz clock signal with PortB used to drive the motors. Using find-and-replace to change the PORTB keywords to use a DEFINE variable should be easy enough, but we don’t know how hard it would be to change the clock frequency.

We wonder if it’s possible to make this a slave device, perhaps implementing a 1-wire protocol?

[Dan’s] office is awfully hot, but he needed some real temperature numbers that he could show the building management office to justify opening a maintenance ticket. He had seen some simple temperature probe examples online, and decided to build his own using a small AVR chip.

Based off a similar temperature monitoring example called EasyLogger, his temperature probe uses an LM34 temperature sensor, which is wired to an ATtiny45. The ATtiny communicates with his computer using the Ruby-USB library in conjunction with a bit of Ruby code he put together. Once the data is obtained, all of the temperature measurements are logged and graphed using RubyRRDTool.

As you can see by in the image above, his office is far hotter than it should be, so we’re pretty sure he’s happy to have actual measurements to back up his claims.

If you are looking to make a small temperature probe of your own, his code, schematics, and links to all of the tools he used in the project are available on his site.

Looking at the size of this bristlebot the first thing we wondered is where’s the battery? All we know is that it’s a rechargeable NiMH and it must be hiding under that tiny circuit board. But [Naghi Sotoudeh] didn’t just build a mindless device that jiggles its way across a table. This vibrating robot is controllable with an infrared remote control. It uses an ATtiny45 microcontroller to monitor an IR receiver for user input. An RC5 compatible television remote control lets you send commands, driving the tiny form factor in more ways than we thought possible. Check out the video after the break to see how well the two vibrating motors work at propelling the device. They’re driven using a PWM signal with makes for better control, but it doesn’t look like there’s any protection circuitry which raises concern for the longevity of the uC.

This build was featured in a larger post over at Hizook which details the history of vibrating robots. It’s not technically a bristlebot since it doesn’t ride on top of a brush, but the concept is the same. You could give your miniature fabrication skills a try in order to replicate this, or you can build a much larger version that is also steerable.

Feeling a bit left out because he didn’t have a PICAXE on hand, [Rob Miles] decided to port the Luna Mod code so that it would work on an AVR chip. He chose to build his around an ATtiny45, but also mentions that this is Arduino compatible.

This case layout is a bit different from the original Make version, but we like this look just a bit better. It might not satisfy your need for that hipster looking enclosure, but the repurposed macadamia nut box looks seems it was built for this purpose. Take a look as the video after the break to see the final product and hear it spewing newly composed cacophony. [Rob] is sharing the sketch as a dropbox file but we’ve also included our own hosted link after the break in case is stops working.

Source Code

Kids love games of exclusion. This usually manifests itself in games of ‘keep away,’ having someone ‘catch cooties,’ or the ever-popular ‘No Brian club.’ [Rob] wrote in to tell us about the digital cootie detector he built. The cootie detector operates on galvanic skin response. It’s actually very similar to an E-Meter, although instead of Thetans this device measures something that actually exists.

Galvanic skin response is a measure of the skin’s conductivity. Skin conductivity changes because sweat glands will be activated when someone is nervous. This is a measure of psychological arousal, making it a great detector for games of exclusion – a kid who doesn’t want cooties will ‘psych themself out’ and give themselves cooties.

The build is based around an ATtiny45 with just a few resistors and paperclips required for a complete build. The ‘Cootie Detection Algorithm’ starts off with a flashing light – a great way to make someone nervous. After the test is completed, a green light means they can enter the quarantined area, while a red light means they must be excluded. There’s also a “device tampered” result – alternating red and green lights – that will show up when a clever child tries to short the paperclip leads. Check out the demo below:

If you are planning on using more than a handful of BlinkMs in a project, you will likely find that their $15 price tag quickly adds up. Instructables user [jimthree] found himself in that position and opted to create his own homebrew version of a BlinkM instead. He calls his creations “Ghetto Pixels”, and while they might not look as professional as the real thing, they get the job done just the same.

He bought a batch of RGB LEDs online for under a dollar apiece, pairing them with ATTiny45s that he scored for about $1.50 each. [imthree] popped his uCs into a programmer, flashing them with an open-source BlinkM firmware clone called CYZ_RGB. He then prototyped his circuit on some breadboard, adding the appropriate resistors to the mix before testing out the LEDs. When he was confident everything was working correctly, he assembled Ghetto Pixels deadbug-style.

When everything was said and done, they came together in a pretty compact package comparable to that of the BlinkM. As you can see in the video below, they work great too!

[Furrtek] hooked up his Game Boy printer for use with a PC (translated). The two-part hack started with a cable to attach the device via USB. A Nokia interface cable was used as a base to translate the USB signals into serial, and an ATtiny45 microcontroller added to talk to the printer. He did a great job of free-forming the circuit alterations and fitting it back into the plastic USB plug housing.The next step was to write some software. Using VB6 he coded an application that loads in an image, scales it to fit, and allows you to adjust the contrast that the thermal printer produces. For testing purposes he’s reusing old receipts. See it in action after the break.

[gpsKlaus] built this little FM radio (translated) based on the AR1010 IC. That chip is controlled via I2C by an ATtiny45 microcontroller. His tuning implementation relies on presetting 16 stations in the firmware and selecting them with the white potentiometer.

The FM chip came on a breakout board from SparkFun. Not bad at around $15 as it includes the crystal, some caps and a few resistors, and you don’t have to try and solder to the fine pitched pads on that minuscule package. We’re a little unsure of the features included in the part as the datasheet is lacking in detail and the reference datasheet that SparkFun includes in the description is obviously for a much more full-featured chip. Still, this would be a fun thing to play around with if you’ve grown tired of blinking LEDs.

If you don’t want to let an integrated circuit do all the heavy lifting try this post for a guide on building your own radio tuner.

Here’s a USB oscilloscope project from a few years back. It’s easy to build on a single-sided PCB and very cheap because it uses just a handful of parts. At the center, an ATtiny45 microcontroller uses its ADC capabilities for the two traces and also handles the USB connectivity. The internal oscillator is used and trimmed up for accuracy by referencing the USB clock. On the PC side of things, a program written in C# displays the data coming over the serial bus. Quick, small, and useful; a schematic, board layout, firmware, and PC software sources are all available for download.

[Thanks Shri]

Giving us a chance to break out the TLAs, [Blair] sent in his latest hack where he embedded an RGB LED into his EeePC to display twitter, pidgin, and email notifications. It is based around the ATtiny45, and requires very few additional parts. He based the project on a foundation of work laid by [Dennis Schulze] on notifications and the work of [Dave Hillier] that used V-USB, a library for implementing USB on AVRs. The entire circuit was done freehand and crammed inside the netbook. He says that it is a lot easier to see notifications, even when the laptop is shut.

Related: Email notification via RGB LED

[xander] built this LED valentine for his loved one. It’s interesting because he used Pyralux, a flexible circuit board material from DuPont. He describes the consistency as “tough plastic tissue-paper”, but had no trouble using standard toner transfer etching. It has an ATtiny45 microcontroller that pulses the 16 LEDs at an approximation of his heart beat. To avoid soldering a bunch of surface mount resistors, he used two constant current shift registers.