Author Archives: batchloaf

€5 PPG – photoplethysmogram amplifier / Arduino circuit

The photoplethysmogram (PPG) is a signal that measures changes in blood volume in some part of the body (e.g. the fingertip) by shining light into the skin and detecting small changes in the level of light absorption that occur due … Continue reading

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Clap detector circuit / AirSpell typing system

This circuit combines a simple audio amplifier (based on an LM358 opamp) with an Arduino Nano to facilitate the detection of clapping sounds or blowing on the microphone. This is my breadboard circuit: I actually used a loudspeaker for my … Continue reading

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AirMouse – control mouse pointer in Linux using one switch or by blowing on microphone

Article under construction! To install xdotool: Bash script (save as “airmouse” and “chmod 755 airmouse” to make it executable): Arduino code:

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Some RGB fractal doodles

Click on the animation to view full size gif. This is the code I used to generate the animation: The version below is obtained by modifying the iterating function on line 59 of the program, as follows: Click on the … Continue reading

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How to display USB webcam as live video on desktop using mplayer

mplayer -tv driver=v4l2:gain=1:width=1280:height=720:device=/dev/video1:fps=10:outfmt=rgb16 tv://

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Ronan Byrne’s ultra low-cost brain-computer interface

Over the years, I’ve dabbled a bit in the creation of a so-called brain-computer interface (BCI). These systems take various forms, but the basic idea is to use technology to transfer information from the conscious mind of a human into … Continue reading

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H-bridge control example for Arduino Nano (ATmega328) – two phase-displaced square waves

This is the code: Example Output In the following oscilloscope screenshots, channel 1 (yellow) displays the signal from OC2 (pin D11) and channel 2 (blue) displays the signal from OC2B (pin D3). This is the output when OC2RB = 49, … Continue reading

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