It’s pretty awesome to get see the number of projects presented at World Maker Faire. But we still love digging into the gritty details that only an in-depth build post can deliver. Here we get both. You can see the circuits pictured above in the Circuit Castle exhibit at WMF this weekend, and you can read about how the microcontroller network was built in [Jim’s] article.
As the title states, this is a network built for a dollhouse. Each slave device performs a different task; adding color, sound, motion, and interactivity using some sensors. The post discusses the i2c (or TWI to get around licensing issues as [Jim] mentions) communications used to talk to the ATtiny85 chips on the slave boards. Because the eight-pin package leaves few I/O pins to work with an ATtiny84 was also added. It brings 14-pins to the party, including multiple ADC inputs for reading sensors.
If this ends up being too much of a read for you jog to the “Update 9/17/13” to get the general overview of progress. Like any project on a timeline, not everything works quite as well as they would have liked it to. But it’s the journey that makes something like this so fun — a fully working project would signal an end to the enjoyment, right?
[via Workshop 88]
[Sebastian] is trying to improve the responsiveness of an electric keyboard. He was unsatisfied with the lack of adequate sensitivity to keystroke. The first step in his process was to measure how fast the quickest keystroke actually is. By setting up an LED and phototransistor and taking some measurements he found that sampling at 1 kHz would be more than adequate.
With initial testing complete he ordered some CNY70 transmissive/reflective light sensors that can be place below the keys. He measures the sensor with the ADC on an ATmega16 microcontroller. Running at 16 MHz he can sample each of the eight analog-to-digital converter channels at 1202 Hz. After doing a bunch of math he put together some lookup tables that are used to translate the ADC data into midi signals. We’ve embedded a video of one sensor controlling the midi program PianoTeq. [Sebastian] also sent us a schematic of one node in the sensor network (see it after the break).
When everything is said and done he plans to use eleven ATmega16 microcontrollers to address the 88 keys, with an additional microcontroller to act as the master using a two-wire interface for communications.
Update: [Sebastian] put up a webpage with a fairly verbose description. Reading it straight from the source really clears up a lot of questions.
Continue reading “Playing piano with optical sensors”