It’s a little known secret that when the Hackaday writers gather in their secret underground bunker to work on our plans for world domination, we often take breaks to play our version of the corporate “Buzzword Bingo”, where paradigms are leveraged and meetings circle back to loop in offline stakeholders, or something like that. Our version, however, is “Comment Line Bingo”, and right in the middle of the card is the seemingly most common comment of all: “You should have used a 555,” or variations thereof.
So it was with vicious glee that we came across the Trollduino V1.0 by the deliciously named [Mild Lee Interested]. It’s the hardware answer to the common complaint, which we’ll grant is often justified. The beautiful part of this is that Trollduino occupies the same footprint as an Arduino Uno and is even pin-compatible with the microcontroller board, or at least sort of. The familiar line of components and connectors sprout from the left edge of the board, and headers for shields line the top and bottom edges too. “Sketches” are implemented in hardware, with jumpers and resistors and capacitors of various values plugged in to achieve all the marvelous configurations the indispensable timer chip can be used for. And extra points for the deliberately provocative use of Comic Sans in the silkscreen.
The vibration-detecting bit is a tiny ball bearing soldered to the spring from an old pen, which is tied between the trigger and ground pins of the 555. When the chip is powered with a 9 V battery, nearby vibrations will induce wiggle in the spring, causing the ball bearing to contact the brass rod and completing the circuit. When this happens, the internal flip flop’s output goes high, which turns on the LED. Then the flip flop must be reset with a momentary button. Check out the build video after the break.
Thanks to a couple of modules, the circuit is really pretty simple. There’s a PIR to detect the animals, a buzzer, and a 555-based pulse generator to play tones through the buzzer. This circuit can run 24/7 on a pair of 6V solar panels that charge up a battery. We particularly like the desk trash can enclosure, though we have to wonder how waterproof this system is. Check out the brief demo after the break.
Some cool-mist humidifiers work by flinging water at a vaporizer, but our favorite kind uses a piezoelectric transducer. These work by using high-frequency sound waves to pound the surface of the water with mechanical energy. That energy introduces standing waves that force the water to break apart into a fine mist on the surface of the piezo disk.
The driving circuit for this DIY mist maker uses a 555 to generate 113 KHz, a trimmer potentiometer to fine-tune it, and a MOSFET to amplify the signal. You don’t need much more than that and a handful of passives to recreate this cool junk box experiment, but the spec of the piezo disk is quite important. The circuit is designed for atomizing transducers, which have a resonant frequency of 113 KHz — much higher than your average junk box piezo. Check out the demo and build video after the break.
If you’re planning to get into circuit sculpture one of these days, it would probably be best to start with something small and simple, instead of trying to make a crazy light-up spaceship or something with a lot of curves on the first go. A small form factor doesn’t necessarily mean it can’t also be useful. Why not start by making a small automatic night light?
The circuit itself is quite simple, especially because it uses an Arduino. You could accomplish the same thing with a 555, but that’s going to complicate the circuit sculpture part of things a bit. As long as the ambient light level coming in from the light-dependent resistor is low enough, then the two LEDs will be lit.
We love the frosted acrylic panels that [akshar1101] connected together with what looks like right angle header pins. If you wanted to expose the electronics, localize the light diffusion with a little acrylic cover that slips over the LEDs. Check it out in the demo after the break.
For many of our readers, the classic 555 timer holds a special place in their heart, and cursed be the fool who dares to use an Arduino in its place. For the seriously devoted ones, or those who simply like a novelty decorative item, [acerlaguinto7] built just the right thing: a giant, actually functional, cardboard 555 timer IC.
Taking all the measurements of the original IC, [acerlaguinto7] scaled it up by factor 22 and started cutting out pieces of cardboard — also considering the orientation notch — and added the markings to emulate TI’s NE555P. Next he took a bunch of aluminum cans apart and shaped them into the pins, again staying as close as possible to the original. To top it all off, he put an actual NE555 inside the giant counterpart, and hooked it up to the soda can pins, turning it into a fully operational, oversized timer IC.
Bats are fascinating animals, and despite all the myth and creepiness surrounding them, they really remind one more of a drunk bird lost in the night sky than the blood-sucking creature they’re often made out to be. Of course, some really fall into that category, and unlike actual birds, bats don’t tend to grace us with their singsong — at least not in ways audible for us humans. But thanks to bat detectors, we can still pick up on it, and [Marcel] recently built a heterodyne bat detector himself.
The detector is made with a 555, an MCP6004 op amp, and a 4066 analog switch — along with a bunch of passives — and is neatly packed into a 3D-printed case with a potentiometer to set the volume and center frequency for the detection. The bat signal itself is picked up by a MEMS microphone with a frequency range [Marcel] found suitable for the task. His write-up also goes in all the mathematics details regarding heterodyning, and how each component plays into that. The resulting audio can be listened to through a headphone output, and after putting together an adapter, can also be recorded from his smartphone. A sample of how that sounds is added in his write-up, which you can also check out after the break.