Laser projector ditches galvanometer for spinning drum

Laser projectors like those popular in clubs or laser shows often use mirror galvanometers to reflect the laser and draw in 2D. Without galvos, and on a tight budget, [Vitaliy Mosesov] decided that instead of downgrading the quality, he would seek an entirely different solution: a spinning mirror drum.

He fires a laser at a rotating drum with twelve mirror faces, each at a different adjustable vertical angle. The laser will hit a higher or lower point on the projection surface depending on which mirror it’s reflecting off – this creates resolution in the Y direction.

Timing the pulsing of the laser so that it reflects off the mirror at a certain horizontal angle provides the X resolution.

As you can already tell, speed and timing is critical for this to work. So much so that [Vitaliy] decided he wanted to overclock his Arduino – from 16 MHz to 24.576 MHz. Since this changes the baud rate, an AVR ISP II was used for programming after the modification, and the ‘duino’s hardware serial initialization had to be hacked too.

For the laser itself, [Vitaliy] designed some nifty driver circuitry, which can respond quickly to the required >50 kHz modulation, supply high current, and filter out voltage transients on the power supply (semiconductor lasers have no protection from current spikes).

On the motor side of things, closed loop control is essential. A photo-interrupter was added to the drum for exact speed detection, as well as a differentiator to clean up the signal. Oh, and did we mention the motor is from a floppy disk drive?

We’ve actually seen builds like this before, including a dot-matrix version with multiple lasers and one made apparently out of Meccano and hot-glue that can project a Jolly Wrencher. But this build, with its multiple, adjustable mirrors, is a beauty.  Check it out in action below.

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Oil Barrel Smoker

What would you do with a pair of oil drums and a craving for delicious food? Like any sane person, redditor [Kilgore_nrw] made the logical choice and built a smoker.

To make the build easier, he picked up a double barrel stove kit which came with a door, hinges, legs and flue connectors. While fixing the legs and mounting the stove door — high enough for a bed of bricks in the fire barrel — went as planned, he had to improvise the installation of the smoke flue. It ended up being the exact same diameter as the flue connectors, but notching it enough to slide into place made a satisfactory seal.

Not liking the look of having the stack at the ‘front’ of the smoker, he mounted it above the flue at the rear and added two sandstone slabs in the smoking chamber to evenly distribute the heat. Finishing touches included heavy duty drawer slides for the cooking rack — ensuring easy access to deliciousness — and painstakingly grinding off the old paint to apply a new heat resistant coating. For any fans out there, the finished pictures are a sight to behold.

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Drum on a Chip–Not That Kind of Chip

Comedian Mitch Hedberg had a theory about Pringles potato chips. His theory is the company formed to make tennis balls. But instead of a truckload of rubber, someone accidentally sent them potatoes, so they made the best of it. Certainly the Pringles can is an iconic brand all by itself. The cans also have a lot of hacker history, since they are commonly used for WiFi cantennas (even though it might not be the best choice of cans). People also use them to build pinhole cameras, macro lenses, and a variety of cannon-like devices.

[Ian H] uses the short Pringles cans to build a drum kit. Clearly, the little cans aren’t going to make very much sound on their own, but with a piezo speaker element used in reverse, the cans become touch sensors that feed an Arduino and drive a MIDI device. You can see a video of the result, below.

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Modular Drum Machine Creates Random Rhythms

Don’t worry, the rhythms themselves aren’t random! That would hardly make for a useful drum machine. [kbob]’s creation does have the ability to randomly generate functional rhythms, though, and it’s all done on a breadboard.

The core of this tiny drum machine is two Teensy dev boards. One is an FM synth tuned to sound like drums, and the other is a random rhythm generator with several controls. The algorithms are from Mutable Instruments’ open source Eurorack modules. The entire thing fits on a breadboard with JIGMOD modules for the user interface. The machine runs on lithium batteries in the form of USB cell phone chargers. The battery holders were designed in Fusion 360 and 3D printed.

The function of the drum machine is pretty interesting as well. There are a set of triggers tied to the buttons on the machine. When a button is pressed, the drum machine plays that sound at the appropriate time, ensuring there are no offbeat beats. The potentiometers are polled once every millisecond and the program updates the output as required. There’s also a “grid” of rhythms that are controlled with two other knobs (one to map the X coordinate and the other for the Y) and a “chaos” button which adds an element of randomness to this mapping.

The modular nature of this project would make this a great instrument to add to one’s musical repertoire.It’s easily customizable, and could fit in with any of a number of other synthesizer instruments.

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DIY Bass Drum Microphone Uses Woofer Cone As Diaphragm

Anyone into audio recording knows that recording drums is a serious pain. Mic setup and positioning can make or break a recording session. One particular hurdle is getting a great sound out of the bass drum. To overcome this, [Mike] has built a microphone using an 8″ woofer in an attempt to capture the low-end frequencies of his bass drum. Using a speaker as a microphone isn’t a new idea and these large diaphragm bass drum mics have taken commercial form as the DW Moon Mic and the now-discontinued Yamaha SubKick.

The project is actually quite simple. The speaker’s positive terminal is connected to Pin 2 of a 3-pin XLR microphone connector. The speaker’s negative terminal is connected to the connector’s Pin 1. [Mike] made a bracket to connect the woofer to a mic stand, which in turn was cut down to position the woofer at bass drum height. The setup is then plugged into a mixer or pre-amp just like any other regular microphone.

[Mike] has since made some changes to his mic configuration. It was putting out way too hot of a signal to the preamp so he added an attenuation circuit between the speaker and XLR connector. Next, he came across an old 10″ tom shell and decided to transplant his speaker-microphone from the open-air metal rack to the aesthetically pleasing drum shell. Check out [Mike’s] project page for some before and after audio samples.

Making a Propane Tank Hank Drum


A [Hank Drum], as explained here, is a steel drum-type instrument made out of a propane tank. The name comes from the [Hang] or [Hang Drum] which is significantly more expensive than that $40 or so an empty propane tank costs. Of course, you’ll have to do some work to get it to play beautiful music, which can be seen in a time-lapse construction video after the break.

The details of how this instrument was made can be found here, including how to lay everything out and cut out eight relatively neat “tongues” for producing different tones. I used a Dremel tool, but this can also be done using saber saw for a curved top. This method is explained here with a template, but the results may not be as neat.

If you want to try this yourself, make sure to use an empty, unused propane tank. This is extremely important. For another entirely different homemade instrument, why not check out the [Whamola] that we made a year or so ago? Continue reading “Making a Propane Tank Hank Drum”

Japanese Drumming Sensei


If you’re looking to learn the art of playing Japanese drums, or Taiko, this hack, done as a school project by [Cornell] students, could be a really helpful aid. The project write-up is very impressive and includes a detailed explanation of their work, the source code, and a bill of materials if you’d like to try to duplicate this device.

The tutor device is able to tell between soft hits, hard hits, and rimshots using a piezoelectric sensor hooked up to an ATmega1284P microcontroller. This data can then be transmitted to the “follower” drum using an infrared transmitter. These beats can be used in several modes including: follow the leader, metronome, repeat after me, and drum battle mode.

Ok, maybe there’s no drum battle mode, but be sure to check out the demonstration of the Taiko teaching aid after the break.  There’s a lot of details about the build, but they start some calibration drumming around 4:00 if you’d just like to see it in action. Continue reading “Japanese Drumming Sensei”