10" Home Lab Testing Rack

For a lot of project development and testing, I’m always using a combination of testing and verifying power via USB, 12VDC, MIDI inputs and outputs, and other general IO. Having equipment and cables strewn everywhere is far from ideal. Having all the various equipment contained in an easy-to-access rack makes things way tidier and reduces incorrect testing.

Most of the testing process runs from Python scripts running on a Raspberry Pi, which also handles database logging and validation. Enter, my build and improvements on the Lab Rax 10” Project. I printed all of the parts on Bambu P1S and A1 printers with a mix of PETG and PLA with a standard 0.4mm nozzle (and if you couldn’t tell by the Purple/Black edge rails, I was using up some half-empty rolls of PETG for some printed parts.

I knew that using a standard format to contain various testing equipment was the way to go, so rather than reinventing the wheel, I had a look at existing projects to base this on. A standard 19” rack would be far too big for a test bench, so a 10” rack is the perfect size to fit everything in, but not take up too much room. The Lab Rax 10” 5U rack by Michael Klements is a fantastic project for a fully 3D printable 10” rack, which provides the chassis for this project. However, in the project write-up, the side panel files are only available as 3D printed files. This is fine if you only have access to a 3D printer, but large, flat surfaces are an inefficient use of filament, and laser cutting is a much more preferable option. Klements references using laser cutting as an option for these, but no files are available, so I made my own. The slots are designed for 3mm material, so 3mm acrylic was the choice here, providing a light-weight, but high-strength option. The side panels are identical and solid; the top and bottom panels are the same size. However, I added a mount for a standard 120mm fan with venting cutouts. For the bottom panel, you can just use the Top Panel file and remove the fan cutout, or keep it if you want a bottom intake fan as well. For the assembly of the rack chassis itself, I’ll refer you to the Lab Rax project page. Apart from the 3D-printed parts, you’ll need M6 10-12mm screws, as well as some 4mm M6 heat-set inserts. These are actually quite difficult to source as 4mm is a fairly niche length for such a large screw size, and you’ll need quite a few of them. I sourced mine from Aliexpress here 

I’ve included all of the files I designed for this project, including the DXF files for the laser-cut panels, which were not available in the Lab Rax file set.

With the chassis built, it was time to design some 10” rack units for the basic parts of the system. First was mounting a Raspberry Pi with an easily accessible display. I chose the

3.5-inch Capacitive Touch Display for Raspberry Pi. It’s a nice IPS display with 5-point touch support and drivers ready to go for the Raspberry Pi. It can be mounted directly to the back of a Pi, but I wanted easier access to the Pi IO throughout the rack. At this point, I wanted to try different connector options and layouts for IO, such as Ethernet, USB, and extra display outputs. The standard D-Socket chassis connectors are ideal to provide a modular approach to this, so in a 2U height, I could fit the display, cutouts for some 12mm panel mount buttons, and 6x D-Socket connectors. These can be installed or left out as desired, but I always prefer to future-proof things with the ability to add more connectors after the fact. On this note, I also added a 20mm grid of M3 heat set inserts to give flexible mounting for both the Pi and other electronics, which may need to be added further on. A basic mounting plate for a Pi easily mounts the Pi to this grid. Because this panel uses a fairly precise, recessed cutout for the display, it worked out better to print the face-plate, shelf, and rear-mounting bracket as separate files and then screw them together. This gives better strength along the filament path direction, as well as printing accuracy.

Next up is some MIDI IO. Whilst you can do standard UART MIDI with a Pi, configuring the UARTs to the non-standard baud rate of 31250, whilst retaining standard GPIO features, provides some challenges, depending on what generation of Raspberry Pi you’re using. A much simpler way is to use a class-compliant USB MIDI interface, which is extremely easy to target with Python scripts. I used an iConnectivity Mio2 that I had lying around to give 2x MIDI In/Out ports, as well as a spare USB device port for multi-device USB routing. The Mio2 has a ¼” threaded socket underneath to make mounting to a rack surface nice and easy. I wanted the front panel of this to be exposed at the front to give easy viewing of the status LEDs and USB connections.
I couldn’t fit 4x D-socket panels in the width, so I used ¼” TRS D-socket connectors to give Type A  

Lastly, for the basic functional build, we need power. As discussed earlier, 12V DC is needed for external equipment (plus 12V fans are much more standard), as well as 5V DC for the Raspberry Pi and other USB equipment. Whilst I could use an internal power board with plug backs, this would add a lot of bulk and internal wiring, which further restricts airflow. Instead, I opted for a high-quality Meanwell industrial power supply. There are lots of options in this form factor, and they are nice and slim, which means I can mount it in a 1U slot instead of a 2U slot (although I’d recommend leaving the slot above free to allow for airflow around the supply).

I used the RD-65A unit, which provides 12V 3A as well as 5V 6A, which gives plenty of headroom for both the Pi and other 5V devices. Alternatively, if you only need 5V, the AM8723 will also fit. There are several power supply options in this small form factor, so you can pick and choose what voltages and current capacity best suits your project.

A standard IEC socket with built-in fusing and power switch feeds the supply. Please note, DO NOT attempt this yourself if you are not confident with the mains wiring. Anything to do with mains power should give you pause, and ideally, find a qualified person to do the wiring for you.

A downside of the RD-65A is that it doesn’t have a plastic cover over the screw terminals. Whilst access to the live conductors shouldn’t come up in general usage, it’s always better to be safe than sorry, and I also wanted to protect against a loose cable potentially falling and making contact with any high voltages. So part of the shelf includes a recessed shield around the wiring run, with inserts for M2.5 screws, which interfaces with a top panel covering all physical access to the mains contacts.