Bats use echolocation to see objects in front of them. They emit an ultrasonic pulse around 20 kHz (and up to 100 kHz) and then sense the pulses as they reflect off an object and back to the bat. It’s the same type of mechanism used by ultrasonic proximity sensors for object-avoidance. Humans (except perhaps the very young ones) can’t hear the ultrasonic pulses since the frequency is too high, but an inexpensive microphone in a simple bat detector could. As it turns out bat detectors are available off the shelf, but where’s the fun in that? So, like any good hacker, [WilkoL] decided to build his own.
[WilkoL’s] design is composed primarily of an electret microphone, microphone preamplifier, CD4040 binary counter, LM386 audio amplifier, and a speaker. Audio signals are analog and their amplitudes vary based on how close the sound is to the microphone. [WilkoL] wanted to pick up bat sounds as far away as possible, so he cranked up the gain of the microphone preamplifier by quite a bit, essentially railing the amplifiers. Since he mostly cares about the frequency of the sound and not the amplitude, he wasn’t concerned about saturating the transistor output.
The CD4040 then divides the signal by a factor of 16, generating an output signal within the audible frequency range of the human ear. A bat signal of 20 kHz divides down to 1.25 kHz and a bat signal of up to 100 kHz divides down to 6.25 kHz.
He was able to test his bat detector with an ultrasonic range finder and by the noise generated from jingling his keychain (apparently there are some pretty non-audible high-frequency components from jingling keys). He hasn’t yet been able to get a recording of his device picking up bats. It has detected bats on a number of occasions, but he was a bit too late to get it on video.
Anyway, we’re definitely looking forward to seeing the bat detector in action! Who knows, maybe he’ll find Batman.
Continue reading “Hack Together Your Own Bat Signal”
While this 3D printed synthesizer might just be okay, we’re going to say it’s better than that. Why? [oskitone] did something with a 555 timer.
The Okay synth from [oskitone] uses a completely 3D printed enclosure. Even the keys are printed. Underneath these keys is a small PCB loaded up with tact switches and small potentiometers. This board runs to another board loaded up with a 555 timer and a CD4040 frequency divider. This, in turn, goes into an LM386 amplifier. It’s more or less the simplest synth you can make.
If this synth looks familiar, you’re right. A few months ago, [oskitone] released the Hello F0 synth, a simple wooden box with 3D printed keys, a few switches, and a single 4046 PLL oscillator. It’s the simplest synth you can build, but it is something that can be extended into a real, proper synthesizer with different waveforms, LFOs, and envelope generators.
The sound of this chip is a very hard square wave with none of the subtleties of A,S,D, or R. Turn down the octave knob and it makes a great bass synth, or turn the octave knob to the middle for some great chiptune tones. All the 3D models for this synth are available on Thingiverse, so if you’d like to print your own, have at it.
You can check out the demo of the Okay synth below.
Continue reading “This Synth Is Okay”
Today we’ll take a journey into less noisy noise, and leave behind the comfortable digital world that we’ve been living in. The payoff? Smoother sounds, because today we start our trip into analog.
If you remember back to our first session when I was explaining how the basic oscillator loads and unloads a capacitor, triggering the output high or low when it crosses two different thresholds. At the time, we pointed out that there was a triangle waveform being generated, but that you’d have a hard time amplifying it without buffering. Today we buffer, and get that triangle wave out to our amplifiers.
But as long as we’re amplifying, we might as well overdrive the amps and head off to the land of distortion. We’ll do just that and build up a triangle-wave oscillator that can morph into a square wave, passing through a rounded-over kinda square wave along the way. The triangle sounds nice and mellow, and the square wave sounds bright and noisy. (You should be used to them by now…) And we get everything in between.
And while we’re at it, we might as well turn the triangle wave into a sawtooth for that nice buzzy-bass sound. Then we can turn the fat sawtooth into a much brighter sounding pulse wave, a near cousin of the square wave above.
What’s making all this work for us? Some dead-boring amplification with negative feedback, and the (mis-)use of a logic chip to get it. After the break I’ll introduce our Chip of the Day: the 4069UB.
If you somehow missed them, here are the first three installments of Logic Noise:
Continue reading “Logic Noise: Sawing Away With Analog Waveforms”
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”
Logic Noise is all about using analog circuits to make sounds. Preferably sound that will be enjoyable to hear and useful for making music. Now, the difference between music, sound, and noise is certainly in the ear of the behearer, but you must admit that last installment’s simple square wave lacked a little something. (Although the sync oscillator circuit extension was kinda cool.)
This week, we’ll take our single wimpy square-wave oscillator and beef it up by adding a bunch of sub-octaves to the mix. And we’ll do it using a chip that’ll be really useful for us in the future as well: the 4040 binary counter chip.
Counters (binary or decimal) are going to be fertile ground for more musical noise experiments. Why so? Because octaves are just doublings or halvings of frequencies, and because a lot of rhythmic patterns have factors of two underlying them. Just think about the most basic drum pattern you know: bass drum on the one, snare on one and three, and hi-hats on one, two, three, and four. Each different instrument fires off twice as frequently as the one before it.
But for now, enough blabber. We’ve got an oscillator to build.
Continue reading “Logic Noise: 8-bits Of Glorious Sounds”