ThunderWave Percussion Ribbon Controller


It's been quite a few years since The Peasant constructed his first Percussion Ribbon Controller and it was time to build something much more versatile and interesting. The goal was to create an instrument that would be both fun to play and able to do amazing things.

While thinking about a new electronic drum synthesizer design, my thoughts had drifted to a couple of long pieces of curved 2cm square aluminum stock sitting in the scrap metal pile. These had previously been salvaged from obsolete equipment and kept as they seemed to have a lot of potential for reuse. Deciding how to best use these metal bars led to a vision of an electronic drum kit consisting of a series of curved ribbon controllers surrounding the drummer, instead of the traditional round drum pads.

Below is a picture of one of the original bars, as well as a piece that had been cut from the second one:

The original vision for the project was of a descending series of curved ribbons magically suspended in space, each one below and in front of the previous one. However, practicality reared it's head and planning for a suitable stand for the ribbons began.

Another dive into the scrap pile provided a variety of suitable parts, with the main theme for the hardware being "shiny aluminum". Work began on cutting and drilling pieces to create the ribbon support.

Below is a picture of the hardware ready for final assembly for the first prototype. It should be noted that every single part that you see here is a salvaged item, no money whatsoever was spent on materials for the project up to this point.

And here is the stand assembled for the first time. This stand is designed for easy disassembly for transport, with the legs held on securely with just one thumbscrew each and the ribbons simply lifted out.

With the ribbon stand completed, work began on designing the actual ribbon mechanism and the supporting circuitry. The instrument would consist of three individual ribbon controllers each with their own electronics section. Outputs would include standard trigger and gate, a control voltage output based on where the ribbon was struck, and a quantizer to break up the length of the ribbon into an adjustable number of zones each providing a distinct control voltage.

An additional "force" trigger output would be included, in which the trigger level would be dependant on how hard the ribbon was struck. This would allow the ribbon to control volume level and other parameters dynamically. The force circuit would also include a pair of force dependant envelope generators for feeding directly into VCA's and other module's CV inputs.

The ribbon's position sensor would come from the resistive element taken from a multi-turn precision wirewound potentiometer. The strike force system would use force sensitive resistors to create the variable trigger. Below is a picture of a ribbon prototype in early development:

And here is one channel of the controller electronics on breadboard:

The final schematic for the project is shown below:

If you would like to read an explanation of how the circuit works, including some building hints, modifications, and upgrades, click the button below:

Once the electronic design was completed, an enclosure was needed for the project. Digging around in the scrap pile again resulted in a pile of shiny aluminum to match the rest of the instrument.

These were assembled into a three-section case with room for all the required circuitry, controls and connectors. At this point the first brand new parts were incorporated into the project, in the form of 13 rivet nuts.

Next, this enclosure was mounted neatly on the stand below the ribbons. The enclosure was also designed to be easily removable from the frame for transport. In this picture the first curved ribbon prototype is shown as well.

Front panel graphics were created for the project, then printed and laminated, ready to be attached.

Here are the three enclosure sections ready to be reassembled into the final unit.

Below is a picture of the assembled case. To each the side of the center panel, two vertical metal bars for mounting power and trigger LEDs were added.

Next is a rear view and an inside look at the enclosure, with and without pc boards installed:

Here are the two printed circuit boards populated and ready to wire in place:

Next are pictures of the enclosure with all of the wiring completed, the main pcb wired into place, and finally a view of the finished assembly. This part of the project used a greater number of new parts than the previous stages, including pc boards, most passive components, semiconductors (not including integrated circuits), potentiometers, and knobs. Of course, non-reusable items like solder, tie wraps, and labelling were also new materials. All wire, ics, sockets, hardware, and most of the connectors were reused salvaged items.

A power supply was next on the list to build. An old electrical box was chosen for the enclosure and all the other necessary parts were gathered up. The only new parts used here were the capacitors and the pcb. Here are all of the parts ready to assemble:

And here is the completed power supply:

The enclosure looks great powered up with the LEDs shining on the front panel. I decided that I preferred lighter colored knobs, so I changed them.

And now on to the ribbons themselves.

The actual ribbon design was developed over a period of months, using a lot of experimentation with different materials and configurations. Durability, output linearity, and consistancy were a few of the goals for the ribbons. They needed to be built using materials that were easily available, without requiring unusual or expensive tools to construct. And mostly they needed to be fun to play, without that "dead" feeling that a lot of percussion drum pads seem to have when you strike them.

The wirewound element taken from a multi-turn precision potentiometer was determined to be a good candidate for the position sensor. These are extremely linear and fairly robust, and although they can be a little expensive, they are readily available from a number of electronic suppliers. I also happened to have a few on hand that had been removed from equipment due to the wiper portion of the potentiometer becoming intermittant. As this project does not use the wiper mechanism, they would be fine to use here.

These elements were subjected to rigorous testing, consisting of being struck with drumsticks thousands of times and with great force, and as there were never any failures experienced, they appeared to be a suitable choice for the project. Cushioning the elements by mounting them on a layer of dense foam tape and adding silicone rubber along their sides provided them with some extra insurance against impact damage.

Having the ribbons respond to the level of force used to strike them was also considered essential for the project. As they are reasonably easy to use and are readily available, force sensitive resistors (FSRs) were chosen for this role.

Creating a ribbon contact mechanism was a challenge, and after evaluating a number of alternatives, it was found that a few layers of copper tape worked well, suspended above the ribbon element with foam rubber. A layer of thick and bouncy rubber tubing laid across the ribbon contact added a very nice "feel" to the ribbons while protecting them from the effects of being repeatably hammered with drum sticks.

Topping off the ribbon was a wrapping of thin flexible rubber sheeting, which finished off and sealed the design in a pleasing manner.

Three final ribbon prototypes were constructed and extensively tested, easily meeting all of the initial goals for the project.

Below is a picture of the completed ribbons. Salvaged parts were used for the ribbons as much as possible, but for non-reusable items such as tape, glue, FSRs, shrink tubing, foam, and rubber parts it was necessary to use new materials.

And here are some pictures of the fully completed project:

You can see in this picture how well the instrument breaks down for transport. Just five easy thumbscrews and it's done!

If you would like to start your own ThunderWave project, press the button below for a detailed guide to building the ribbons from start to finish, including a helpful video.

Below is a video demonstrating the features and abilities of the ThunderWave:

And here is a video of the ThunderWave in action, patched into The Peasant's SynthCase system:

The ThunderWave has turned out to be an amazing instrument that is genuinely fun to play. The expressiveness and versatility of it's design has far exceeded my expectations. And using salvaged parts as much as possible made it a very inexpensive build. Best of all, anyone who wants to can build their own!


Don't forget to check out The Peasant's SynthCase projects: SynthCase 1, SynthCase 2 and SynthCase 3!