Update: Many Improvements To Optical-sensor-based Piano

June 5, 2012 by Mike Szczys 2 Comments

[Sebastian] wrote in to update us about the optical sensor project he started a couple of years ago. You’ll find his most recent update here, but there are four different post links after the break that document various parts of his progress.

You may not recall the original project, but he was looking to add resolution and sensitivity to the keystroke of an electric keyboard. With the sensors built, he started experimenting with using the force data to affect other parts of the sound. His post back in January shows this bending the pitch as the keys receive more force from the player.

In March he installed the sensor array in an old piano. The video he posted where he plays the piano, but we hear the sound generated from the sensor inputs. We’ve embedded it after the break.

Last week he published two posts. They cover a redesign of the sensor boards, and the panelization work he’s done to help bring down manufacturing costs. The base unit was redesigned to use an AT90USB microcontroller which consolidates the separate chips used in the previous version.

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Logging Bubble Frequency And Pressure In Your Fermenter

October 24, 2011 by Mike Szczys 21 Comments

In an attempt to add technology to his brewing process [hpux735] build a sensor rig that monitors bubbles and pressure during fermentation. What does this have to do with brewing great beer? We’re not sure and neither is [hpux735], but he’s got some preliminary readings to spark your imagination.

The bubble sensor itself was inspired by a SparkFun Tutorial where fermenting wine was monitored with a data logger. It uses an optical gate to detect the passage of air. But the goal here was to combine bubble frequency with internal pressure measurements to calculate how much CO2 is being vented. Perhaps it would be possible to get an idea of how close the batch is to completion based on those calculations. A hole was drilled into the fermenter side of an airlock to take these pressure readings.

This actually works quite well during secondary fermentation when the bubble frequency is quite slow. The hardware is able to discern a pressure difference before and after a bubble has passed the lock. Unfortunately the system breaks down during the vigorous bubbling that takes place soon after pitching yeast. See a few bubble-counting clips in the video after the break.

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Playing Piano With Optical Sensors

October 7, 2010 by Mike Szczys 16 Comments

[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.

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A Collection Of Quick Line-followers

August 13, 2010 by Mike Szczys 18 Comments

Here’s a nice collection of line-following robots (translated). They’re fast and they stay on track even through sharp turns. They center around a Baby Orangutan board which features an ATmega328 microcontroller and two motor driver channels. These drive the geared motors and use optical sensors to track a dark line on a light surface. There’s plenty of build and testing information (translated) if you’re interested in the gory details. Or just jump past the break to see the red on doing its thing.

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DIY Scratch Controller

March 11, 2010 by Mike Szczys 38 Comments

[youtube=http://www.youtube.com/watch?v=eHI2q-x0ke0]

There’s something viscerally pleasing about simple solutions. [Kip] came up with one in the form of a scratch controller. The spindle from an optical drive is used to hold a CD in place, which acts as the LP for scratching. The sensor from an optical mouse is mounted upside down below the CD and detects the rotation of the disc. From there it’s just a matter of setting up your software to get the reading from that mouse. He’s had some trouble finding disc surfaces that the mouse sensor will read reliably. We’d recommend trying some of those stick-on inkjet CD labels.

This is similar to a scratch controller we saw in 2008. That one was actually repurposing the IR encoding from inside of a mouse. We’re not sure which method would work better, but either controller will make a nice addition to a Flexi Knob setup.