Tachometer Uses Light, Arduinos

To measure how fast something spins, most of us will reach for a tachometer without thinking much about how it works. Tachometers are often found in cars to measure engine RPM, but handheld units can be used for measuring the speed of rotation for other things as well. While some have mechanical shafts that must make physical contact with whatever you’re trying to measure, [electronoobs] has created a contactless tachometer that uses infrared light to take RPM measurements instead.

The tool uses an infrared emitter/detector pair along with an op amp to sense revolution speed. The signal from the IR detector is passed through an op amp in order to improve the quality of the signal and then that is fed into an Arduino. The device also features an OLED screen and a fine-tuning potentiometer all within its own self-contained, 3D-printed case and is powered by a 9 V battery, and can measure up to 10,000 RPM.

The only downside to this design is that a piece of white tape needs to be applied to the subject in order to get the IR detector to work properly, but this is an acceptable tradeoff for not having to make physical contact with a high-speed rotating shaft. All of the schematics and G code are available on the project site too if you want to build your own, and if you’re curious as to what other tools Arduinos have been used in be sure to check out the Arduino-based precision jig.

Continue reading “Tachometer Uses Light, Arduinos”

Follow the Bouncing Ball of Entropy

When [::vtol::] wants to generate random numbers he doesn’t simply type rand() into his Arduino IDE, no, he builds a piece of art. It all starts with a knob, presumably connected to a potentiometer, which sets a frequency. An Arduino UNO takes the reading and generates a tone for an upward-facing speaker. A tiny ball bounces on that speaker where it occasionally collides with a piezoelectric element. The intervals between collisions become our sufficiently random number.

The generated number travels up the Rube Goldberg-esque machine to an LCD mounted at the top where a word, corresponding to our generated number, is displayed. As long as the button is held, a tone will continue to sound and words will be generated so poetry pours forth.

If this take on beat poetry doesn’t suit you, the construction of the Ball-O-Bol has an aesthetic quality that’s eye-catching, whereas projects like his Tape-Head Robot That Listens to the Floor and 8-Bit Digital Photo Gun showed the electronic guts front and center with their own appeal.

Continue reading “Follow the Bouncing Ball of Entropy”

Glitching Square Wave Clock Is Designed To Confuse

[Voja Antonic] has built a clock that tells the time in binary with square waves, and trolls the uninitiated in electronics.

The clock itself is very attractive. If you look closely you can see the circuitry backlit behind the dot LED matrix display. The whole thing is housed in a nicely folded steel case. RGB LEDs are used to good effect to highlight some additionally obfuscating circuit schematics. The workmanship is very top notch, and we would gladly host such an object on our desks.

The clock’s standard time telling mode is three sets of square waves showing the binary values for the hours, minutes, and seconds. Every now and then the clock will glitch out. The waves will distort. The colors will change. And every now and then, tantalizingly, the alpha-numeric time will show up for just a split second, before returning to those weird squiggles again.

We’ve seen a whole slew of binary clocks before. This one, for instance. But the waveform display makes us feel just that little bit more at home — it’s just like we’re sitting in front of our oscilloscope.

Logic Noise: The Switching Sequencer Has the Beat

Logic Noise is all about using logic circuits to make sounds. Preferably sound that will be enjoyable to hear and useful for making music. This week, we’ll be scratching the surface of one of my favorite chips to use and abuse for, well, nearly anything: the 4051 8-way analog switch. As the name suggests, you can hook up eight inputs and select one from among them to be connected up to the output. (Alternatively, you can send a single input to one of eight destinations, but we won’t be doing that here.)

Why is this cool? Well, imagine that you wanted to make our oscillator play eight notes. If you worked through our first installment, you built an abrasive-sounding but versatile oscillator. I had you tapping manually on eight different resistors or turning a potentiometer to eight different positions. This week, we’ll be letting the 4051 take over some of the controls, leaving us to do the more advanced knob twiddling.

Continue reading “Logic Noise: The Switching Sequencer Has the Beat”

Sine Waves, Squares Waves, and the Occasional FFT

I became aware of harmonics and the sound of different shaped waveforms early in my electronics career (mid 1970’s) as I was an avid fan of [Emerson Lake and Palmer], [Pink Floyd], [Yes], and the list goes on. I knew every note of [Karn Evil 9] and could hear the sweeping filters and the fundamental wave shapes underneath it.

bil1

I remember coming to the understanding that a square wave, which is a collection of fundamental and (odd) harmonics frequencies, could then be used to give an indication of frequency response. If the high frequencies were missing the sharp edges of the square wave would round off. The opposite was then true, if the low frequencies were missing the square wave couldn’t “hold” its value and the top plateau would start to sag.

Continue reading “Sine Waves, Squares Waves, and the Occasional FFT”