Attiny25 Based Function Generator Causes A Wave

February 8, 2012 by Kevin Dady 11 Comments

Function generators are a handy bench tool to have around, and while you can usually cobble something together that works, it is much more handy to grab a device when you need it. Thats where this function generator sent to us by [Mohonri]comes in. Based around a ATTiny25 and a rail to rail op amp which is able to replicate frequencies from 1Hz to about 40KHz, in square, triangle, and sinewaves simultaneously.

The function generator also features independent amplitude control on each output. And it’s all on one palm-sized, single-sided PCB. The main part of the code is split into two parts: the main loop gets the inputs and constructs a waveform table in SRAM, and then an ISR reads that table and outputs it to one of the timers, which produces a PWM output, which is low-pass-filtered and then passes through a potentiometer (for amplitude control) and then to an op-amp before landing on a set of terminals.

Though its not 100% perfect, trading speed for a 6 bit resolution, it should be more than enough for most electronic projects. You can pick it up in kit form from the on-line shop, but schematics, software and PCB layouts are also available for download.

[Sprite_tm]’s Three-component FM Transmitter

January 26, 2012 by Brian Benchoff 54 Comments

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.

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A Simple, Self-contained 7-segment Display

January 24, 2012 by Mike Nathan 13 Comments

self-contained-7-seg

It’s no secret that seven-segment displays are an easy and useful way to relay data, so [Kelvyn Panici] decided to put together a minimalst, self-contained display for use around the house.

The display itself is a 16-digit model he picked up from DealExtreme for under $10. He wanted to find a microcontroller small enough to fit behind the display’s footprint, so he chose an ATtiny85 to control it. After mounting the mcu on a small piece of perfboard, he burned the Arduino bootloader and uploaded a small sketch to drive the display.

Things worked out quite well as you can see by the video below where he shows off a pre-perfboard prototype. [Kelvyn] currently does not have any immediate projects in the works that will utilize the display, though there are a plethora of possibilities. We think it would work great anywhere if it were fitted with a battery and some sort of wireless radio in order to make it completely self-contained.

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A Little Simon Clone Named [Nomis]

January 6, 2012 by Jeremy Cook 3 Comments

[Chris] has been hard at work building his own version of Simon called [Nomis]. Although [HAD] has featured an ATiny Simon clone before, the article does an excellent job explaining how the system works.

The ATTiny85 is used to control this game, which, for now is laid out on a simple breadboard. A PCB version of this game has been ordered from [Seeed], so be sure to check back to see the results of this forthcoming upgrade. It’s really cool that this kind of small scale manufacturing is available to the masses.

A parts list is provided as well as a code overview and schematic. To see it in action, check out the video after the break. There’s an explanation at the beginning, but skip to 1:55 if you’d rather just see the machine in action. The game can reportedly run until a 100 “move” limit is reached. This was arbitrary, but it should be enough for most people! Continue reading “A Little Simon Clone Named [Nomis]” →

Musical [Blinky] Candy Tin

December 5, 2011 by Brian Benchoff 8 Comments

Since it’s the holidays and pine trees are being cut down and installed in living rooms all around the world, [Jarv] though it would be a good idea to make a musical Christmas ornament. He needed to keep some of his geek cred, so [Jarv] decided to build a musical [Blinky] ghost from Pacman.

A few weeks ago, [Jarv] sent in his musical greeting card that uses a minimal amount of parts to play a short 8-bit tune. His project was based around an ATtiny85 and sounded pretty good. For his [Blinky] ornament, [Jarv] used a similar circuit along with some old-school Pacman songs that sound great.

[Jarv] found a [Blinky] candy tin and after dispensing with all that pressed sugar began work on his build. In keeping with his greeting card, everything is very minimal. Just a speaker, ATtiny85, and button make up the build. Pressing the button cycles through three songs from Ms. Pacman. The result sounds uncannily like a vintage arcade game, so be sure to check out the video after the break.

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Musical Greeting Card With Minimal Parts

November 22, 2011 by Brian Benchoff 26 Comments

We’re all familiar with those musical greeting cards. Give the Hallmark store $10, and you have a card with a microcontroller inside that plays one of several songs available. [Jarv] was playing around with translating MIDI tracks to square wave songs with an Arduino earlier, so he decided to see how cheaply he could reproduce these musical cards. The resulting build allows him to put any song he wants in his card and costs less than the Hallmark offering.

The circuit is extremely minimal – just an ATtiny 85, a battery holder, and two piezo speakers for two-voice harmony. After soldering up the battery and speakers, [Jarv] needed a way to get music on his chip. For this, he used MuseScore, a music notation program that allows [Jarv] to merge multiple voices together.

Once the sheet music was cleaned up, [Jarv] used his XML2H Python script that takes MIDI data and spits out frequencies and delays. In the end, [Jarv] spent less than $5 on his greeting card – almost cheap enough to start thinking about musical throwies to complement the batteries, LEDs and magnets on our window flashing.

Check out the video after the break to hear [Jarv]’s circuit play the theme from Toy Story.

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DIY Thermostat Keeps The Harsh Winter Cold At Bay

October 27, 2011 by Mike Nathan 13 Comments

diy_attiny_thermostat

[Phil’s] parents grow their own organic food, but the harsh Ukraine winters make storing it a difficult proposition. Since it can drop to -30°C on occasion, they asked him to find a way to keep their storeroom at around 5-7°C above zero. He decided to construct his own programmable thermostat to keep things in check, and has been documenting the process as he goes along.

The thermostat uses a DS18B20 temperature sensor to monitor the room, and the logic is handled by an ATtiny2313. When the temperature dips low enough, the ATtiny triggers the room’s heater via a standard 240v relay. He can check the current temperature via a small 7-segment display mounted on the control board, which also contains three microswitches for controlling the heater.

It looks like a pretty solid build so far, and while he hasn’t finished coding the thermostat just yet, [Phil] says that those details are forthcoming. He has published a schematic however, so you can get a jump start on building your own if you’re looking to warm things up this winter.

Continue reading to see a video overview of the thermostat’s design.

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