A Control Panel for Electronics Prototypes — oxblog

Every prototype needing human input starts with the same chore: wire loose<br>buttons, LEDs and a potentiometer before testing the interesting part. So I made<br>that recurring mess permanent.

This scrap-built, 3D-printed panel has four momentary buttons, two toggles, one<br>potentiometer and three LEDs. Ten controls and indicators connect to any<br>microcontroller through ordinary jumper wires. It is a reusable physical<br>interface I can bring to a prototype instead of rebuilding inside it.

The first version: entirely scrap-bin electronics in a printed shell.

What is connected

One side of every button and toggle connects to common ground; the other reaches<br>a front header. With a microcontroller’s pull-up enabled, closing a control<br>pulls its input low.

The potentiometer exposes ground, its wiper and its other end, letting the<br>prototype choose the voltage across the track and feed the wiper to an analogue<br>input.

Each LED’s anode takes power from VIN while a MOSFET switches its cathode to<br>ground. The microcontroller drives only the MOSFET gate rather than supplying<br>LED current through a potentially weak GPIO pin. Current limiting must still<br>suit the LEDs and VIN.

The female headers sit flush with the front face and accept ordinary jumper<br>wires.

Why a separate panel

These are simple circuits, but rebuilding them consumes breadboard space,<br>jumper wires and attention. Loose controls also make interaction testing<br>needlessly awkward, and every rebuild creates another chance to debug wiring<br>that has nothing to do with the prototype.

I found large switch consoles and boards for individual controls, but little in<br>the useful middle: fewer than a dozen mixed controls in a small,<br>microcontroller-agnostic package. This panel is bench infrastructure, not part<br>of the product under test.

The next version

What I plan to add:

Expose both ends of every button and toggle.

Add selectable pull-up/down behaviour and debounced outputs.

Regulate LED power for a wider VIN range.

Make the PCB structural, possibly replacing the case entirely. It is a<br>maker tool; the board does not need to hide.

Make it prettier and add a writable labelling area.

A magnetic base.

Mechanical-keyboard-style buttons.

Wireless control after the physical interface is right.

What I plan to leave out:

LCD, e-ink and other displays.

Joysticks.

Displays and joysticks would turn this into another development board. The aim<br>is to make common physical controls instant, not to add protocols, software and<br>application-specific behaviour.

Design Philosophy

I surveyed projects on the web, estimated the 90th-percentile count for each<br>ordinary control and took roughly half. I then adjusted the numbers for a<br>pleasant arrangement and removed specialty inputs. This was an informal guard<br>against feature creep, not a scientific measurement: enough for common<br>projects, without designing for every outlier.

Placement follows the hand. Frequently used buttons sit at the bottom, clear of<br>everything else. The taller, less-used toggles and potentiometer occupy the<br>middle, reducing accidental knocks. LEDs sit at the top, above the working hand,<br>where they remain visible.

The flat case has conic, continuously curved corners—a simple, pleasant shape<br>without the harsh curvature changes of ordinary rounded rectangles, like a<br>squircle. Flat sides allow compact storage or standing on an edge; flush<br>headers keep the front equally clean.