PS/2 Synth Will Knock You Off Your Broom


Here’s a hack centered around something a lot of people have sitting around: a PS/2 keyboard. [serdef] turned a Harry Potter-edition PS/2 into a combination synth keyboard and drum machine and has a nice write-up about it on

For communication, he tore up a PS/2 to USB cable to get a female mini DIN connector and wired it to the Nano. He’s using a Dreamblaster S1 synth module to generate sounds, and that sits on a synth shield along with the Nano. The synth can be powered from either the USB or a 9-volt.

Keymapping is done with the Teensy PS/2 keyboard library. [serdef] reused a bunch of code from his bicycle drummer project which also employed the Dreamblaster S1. [serdef] is continually adding features to this project, like a pot for resonance control which lets him shape the waveform like an analog synth. He has posted some handy PS/2 integration code, his synth code, and a KiCad schematic. Demo videos are waiting for you across the link.  [Read more...]

Tempo Keeping Drummer Leaves Viking Ship, Now Inspires Pedallers

Bike Controlled Drum Machine

[Serdef] wrote in to tell us about a project he has recently created. It’s a drum beat generator that changes tempo depending on how fast you pedal your bike. This flies directly in the face of using music to keep your pedal timing consistent and up to speed.

The project started out with a tap-tempo drum rhythm pedal that [Serdef] had previously built. This device will generate a drum beat at a tempo corosponding with the time between 2 input signals. This type of device allows someone, say a guitarist, to quickly and easily specify the speed of the drumbeat that they are playing along with.

With the meat and potatoes of the project already figured out, the next part was to make the speed of the bike trigger the tempo of the drum beat. For the signal input, a magnet mounted on the wheel triggers a reed switch mounted on the bike fork once per wheel revolution. This is the same method of information gathering that a bicycle speedometer/odometer uses.

The business part of this project includes an Arduino that measures the speed of the wheel via the magnetic switch, adjusts the speed of the drum beat, and then sends the drum beat to a synthesizer via MIDI protocol. The synthesizer converts the MIDI signal into drum sounds amplified through a powered speaker that the rider can hear. The entire system is powered by a 9v battery and housed in a project box strapped to the bike’s handlebars.

All of the design files and Arduino code are available via [Serdef's] excellent write up on in case you’re interested in making one for yourself.

Analog Drum Machine

Drum Machine Schematic

This analog drum machine project synthesizes a kick and snare drum that are clocked to a beat. It pulls together a few analog circuits to do the timing and synthesis.

The beat timing is a product of a hysteretic oscillator used to create a ‘shark wave,’ which is a friendly term for the output of a relaxation oscillator. This waveform can be compared to a set point using a comparator to create a slow square wave that clocks the drum beat.

The kick drum is synthesized using another hysteretic oscillator, but at a higher frequency, creating a triangle-like waveform at 265 Hz that provides a bass sound. The snare, however, uses white noise provided by a BJT’s P-N junction, which is reverse biased and then amplified. You can spot this transistor because its collector is not connected.

The resulting snare and kick drum wave forms are gated by two transistors into the output. Controlling these gates allows the user to create a drum beat. After the break, check out a video walk-through and a demo of the build.

[Read more...]

Pair of MIDI dongles to inspire some weekend music hacking


This pair of dongles is a fun way to get your feet wet working with MIDI hardware. They’re called MIDIvampire-I and MIDIvampire-II. Just plug one end into your MIDI-ready instrument and the other into a pair of speakers and you’re off and running. Mark I is a polyphonic synth, and Mark II is a drum machine, but both use basically the same hardware which you may already have on hand.

The single chip on each board is an ATmega328 often found anchoring Arduino boards. The other silicon component is an S1112B30MC voltage regulator. The rest of the components are passives, with MIDI and headphone jacks for connectivity. They’re selling these if you want the easy way out, but we thought we’d bring them to your attention in case you needed a breadboarding project this weekend. The firmware, BOM, schematic, and board artwork are all available on the Wiki pages linked in the articles above. After the break you can see a couple of demo videos which walk through all of the features.

[Read more...]

MR-808 is a mechanical version of the most famous drum machine

Anyone who has listened to any music from the 80s has heard the percussive effects of the infamous TR-808 drum machine. To the modern ear, it sounds like an antique. Being the most popular drum machine of all time means it must have some redeeming qualities, right?

[Moritz Simon Geist] decided he wanted nothing to do with the wimpy computer-based emulations of a TR-808. Instead, he chose a more mechanical version that puts robots inside a gigantic 808 enclosure to play snares, high hats, cowbells, and drums in time with any MIDI drum track.

[Moritz] calls his build the MR-808 and puts a real-life bass drum, snares, hats, toms, claps, and a ride into a 3.3 x 1.7 meter ( 10.8 x 5.5 foot) case. The sound triggers are handled by Max/Msp communicating with a pair of Arduinos to handle the solenoids and light effects. You can read more about the hardware setup in [Moritz]‘ behind the scenes look.

After the break you can see the MR-808 in action, both alone and by providing the percussion for [Moritz]‘ band. A very cool build that now cries out for an Arduinofied bassist placed into an overgrown TB-303 enclosure.

[Read more...]

7400 drum machine is a delight

[74hc595] just finished his entry in the 7400 logic contest. It’s a drum machine built entirely from 7400-series logic chips. He hasn’t quite reached full completion of the project yet. The hardware works just fine, and he’s built a foam core face plate with many more controls than you see here but much of the circuit is still on a breadboard at this point and only two of the channels have been complete thus far.

Jump to the video clip after the break to get the details of how the system works and to hear it in action. This demonstration is one of the best we’ve seen for a synthesizer project as he actually talks about what each control does, and how that is accomplished with the hardware. We’re not going to go into detail about the circuitry he’s designed. As we said before, it uses 7400 logic but also sources a 555 timer to keep the beat. The page linked above has a PDF of the schematic available and you could really lose a lot of time studying how he did this. We might even try to build it in a simulator to see what we can learn.

[Read more...]

Adding MIDI to a very old drum machine

Long before drum machines played samples from an SD card or EPROM, drum sounds were analog – just filtered waveforms and noise. To the modern eye, these are very primitive machines, but for [Andrew], they’re the inspiration for this brilliant hack.

[Andrew] took a Roland CR-68 drum machine from 1978 and added MIDI input with the help of a PIC microcontroller. Not wanting to modify the look of the machine, [Andrew] programmed the PIC to watch the START/STOP button when the the unit is powered on. If the button is held down, the PIC enters it’s programming mode, where the sounds from the CR-68 can be mapped to an individual note on a MIDI controller. There’s no mention if the TRIGGER IN is queried by the PIC to modify the tempo of the preset patterns, but we assume that would be a relatively trivial implementation. Still, very impressive for a machine made 4 years before MIDI.

We love [Andrew]‘s work, and we’re happy for any future owner that he documented how to use his device (and cleverly taped that to the bottom of the drum machine). It’s very nice to see old drum machines being used for more than doorstops after their samples have been recorded. Check out the video of [Andrew]‘s walk through after the break.

[Read more...]


Get every new post delivered to your Inbox.

Join 91,306 other followers