FISHERS (project pt.3)

 -PLANNING THE INTERFACE:

The first step in designing the faceplates and arranging the hardware layout, is taking careful measurements of the keyboard enclosure, and drawing it up in my design software. It is important that the working perimeters of the drawing are as close to accurate as possible, so that I know the added hardware will all fit properly.

For more than 10 years now, I have been using an ancient version of CorelDraw for drawing my faceplates and other parts that can be cut from my laser cutter. I also use it for making diagrams and manuals. It is criminally outdated, and I should really upgrade to something better, but at the same time I know how to use CorelDraw to get what I need quickly, so I just have to suffer with its bugs and quirks. 

The keyboard enclosure has a lot of space to work with for adding additional hardware and circuit boards, but there are a few plastic standoff posts that are used to screw the keyboard enclosure back together that I will have to work around so that the keyboard can be reassembled back the way it was designed. It would probably be fine if I had to cut out one or two of the standoffs, but I prefer to keep them when I can to retain the original stability of the keyboard once it is reassembled. I will be removing a lot of plastic from the front of the enclosure for the added interface, so it is good practice to keep as much of the original structure intact. 

Measuring large enclosures like this is never 100% accurate, but gives me a good idea of how much space I have to work with, and I always design things with a large margin for error so that if something needs to be shifted 3-5mm in any direction, I won't have to do a redesign. This usually works out, but not always. 

Once the boundaries are determined, I am then able to come up with a plan for how to divide the faceplate and circuit board dimensions. Over time, I have learned that it is always best to design the whole structure and plan for how the circuit boards will be mounted before coming up with the interface layout. It seems like an obvious step, but it is easy to get excited about the layout, and put off the structural details, and that can be a headache later. 

I decided to break up the interface into three sections since my laser cutter has a pretty small working are, and the faceplates can only be so wide. This works out well because then each faceplate panel can have its own circuit board. Having several smaller circuit boards is also better than having one large one. The cost of smaller circuit boards is less, and if there is a mistake on one board that needs to be redesigned, the section can be replaced easier than the whole thing. It is also better to be able to reposition circuit board in the enclosure if need be, and makes debugging simpler later on if and when the sections need to be disassembled individually to be changed or fixed.

In CorelDraw, I have a collection of hardware footprints that I have hand drawn from the dimensional drawings in the official datasheets of the parts themselves. Switches, potentiometers, LED's, standoffs and various other parts that I have on hand can easily be arranged in the workable area of the enclosure to design my interface. I start by creating a collection of all of the hardware I intend to use, and labeling each part with a parameter name. Then I spend a few days arranging the parts of each section in different ways so that they will all kind of match in alignment and spacing, but also be intuitive to use. 

It is good to decide what kind of knobs are going to be used prior to committing to a layout design, because there will not always be enough space for everything. Some parameters only really need a small knob, and using smaller knobs when I can leaves more space for larger knobs in other areas where I would want them. 

Choosing knobs can be tricky, because I never know what knobs I have on hand, and you never really know if they are going to fit the style until they actually arrive. I usually order knobs from Aliexpress because there are so many more varieties to choose from, and I really want my interface to be unique. The downside of this is that availability and consistency is always an unknown, and certain knob styles that I have used in the past can just disappear completely from the marketplace.

I tend to plan for only using two types of knobs per project now–one small style(10-12mm), and one medium style(14-18mm). This way I know whatever knobs I am able to source will fit within the graphics that I use for my interface design.

After coming up with a good plan for the layout of the hardware, I then draw in the graphics to the parameters to indicate their function, and try to make it clear what every knob and switch does without taking up too much space. This can be a challenge when a parameter has a long name and the part is in a cramped position. I find it's best to just keep everything simple but concise so that it all kind of matches a similar style. 

The graphic lines and gauge-scales around the potentiometer knobs are just there to give the instrument some flair and occasionally tie certain parameter sections together to make the parameters easier to understand. The line graphics I chose probably look pretty minimal, but I probably spent too much time on this step, making sure to try an create an overall balanced style that is easy to understand, but has some pop.

The interface will be broken up into the Sequencer section(left), the Voice section(middle), and the Joystick section(right). The Sequencer section has a lot of hardware, and will be a tight fit. I really want to be able to fit as much of the circuitry as I can on the hardware circuit board too, but I can figure that out when the time comes... The Voice section is a little bit more sparse for hardware, but the section is a little more cramped due to the enclosure standoff in the upper-right corner. I think it is good to have the Voice section centered, though. The Joystick section will also have the EG's, and has a little bit more room to work with. It's also a good place for volume and pitch controls. 

The joystick itself is not going to be mounted to a circuit board, so the section to the left of the joystick where the three depth controls and their corresponding LED's are located, will need their own small circuit board to be mounted to. Rather than just having the section's circuit board have an extension to the lower hardware, I decided to just create a small daughter-board that I can easily engrave and cut with my mini-CNC mill. This will reduce the overall dimensions, and the cost of the section's circuit board.

Daughter-board for 'Depth' knobs and LEDs

Since the Joystick section is over the area of the enclosure where the internal speaker used to be I will have top put a speaker somewhere else, and since there is a relatively large sloped area on the enclosure directly below the joystick section, the plan is to put a small 30x70mm rectangular speaker there. I can use my hot-wire plastic bender to bend the joystick faceplate over the edge of the sloped section, and cut mounting holes and a grill for the speaker to be attached. The smaller speaker might not sound as good in that space, but I think having a speaker at all is better than just having the keyboard be line-out only.

Capacitive touch module

The circuit board for the 8 capacitive touch keys fit well in a small section below the keys on the lower right side. It would have been more ideal to have on the left side closer to the sequencer, but there were screw-posts that would have had to be compromised to make space for the circuit board, and I didn't like the Idea of anything around the keys potentially being loose or unstable if an enclosure screw was removed. It might be better that there is more space between the touch keys and the sequencer anyway. It's more balanced that way.

Part 4 coming soon...