OFMG Guitar

The OFMG - our new custom guitar project

We made our first custom guitar about a dozen years ago, but at the time things like 3D printing and low-cost, powerful multi-core microprocessors were not available and to make the guitar into a real product was not feasible. Things have changed a lot in the years since and we can now take advantage of the advances in technology to make something I couldn’t have even dreamed of all those years ago!

The OFMG (Open Frame Modular Guitar) is our take on a what the ideal Rock Band/Guitar Hero/Clone Hero guitar should be. The primary goals are:

• Make it reliable - using long-life components and making it easy to replace parts (especially switches). Strum switches can be replaced without any soldering.

• Make it fun - incorporate active LED lighting on every button to provide feedback and excitement.

• Make it customizable and expandable - with open source firmware anyone can modify features. The included expansion port allows for connecting all kinds of peripherals for future capabilities we haven’t even thought of yet. The guitar body is separate from the “core” of the guitar (the neck and strummer) so almost any style of body can be accommodated. Custom bodies can be 3D-printed, or made from wood.

Roadmap

Note that we are not putting exact dates on the milestones to allow plenty of time for testing and feedback before we move to the next step. We are currently finishing up the 1st step (mechanical tests).

1. Mechanical Test Units - not electrically functional, using 3D-printed PCBs to check mechanical fit and operation of parts. We use these to both test the mechanical fit of the parts, and to test the “feel” of playing. This is perhaps the most time-consuming step, but is critical since most of the major design decisions will be made at this step.

2. Engineering Prototypes - incorporates functional electronics, but may use some “breadboard” or off-the-shelf circuitry. Used for software/firmware development, and a few are sent to key testers for feedback.

3. Pre-production Prototypes - uses 1st run of production PCBs, but firmware/software may not be feature complete. These will be sent to beta testers for play testing and feedback.

4. Initial Production Run - uses revised PCBs (if necessary) and incorporates all the changes from previous versions. These will be sent to early adopters.

Latest Updates

[Sept 19, 2024] For the last couple weeks I’ve been concentrating on getting the neck design finalized. We’ve printed out a few prototypes, did some testing, made revisions, and now have a design that we can move forward with.

Below are some pictures of the neck assembly — the design is modular and the guitar can be built with either one or two sets of fret buttons (using just one set of frets makes the guitar more compact for those with limited space). The firmware can be programmed to operate either set of frets as “solo” buttons. (In some games the solo buttons allow you to play notes without strumming).

The neck structure is built on a set of aluminum rods with rigid PCBs attached via brackets. Covers are then installed over the assembly, and it’s then bolted on to the main core of the guitar.

Each button has a programmable LED underneath it which shines through a specially printed keycap. The switches are low-profile mechanical keyboard switches.