Phase 1 Desk Test Wiring
No-solder bench layout for the door unlocker prototype. The servo gets direct battery power; the XIAO only handles logic power and the PWM control signal through the breadboard.
Clean bench wiring map
Wires use fixed lanes so nothing needs to sit on top of the parts.
Buck mode: battery powers the servo and the XIAO through the buck after the output is set to 5.0V.
Do not plug USB-C into the XIAO while buck 5V is connected to 5V/VBUS.
Battery +
Ground
5V logic
PWM signal
High-current path
2S battery
7.4V nominal, 8.4V full
XT30 output
battery ground
XT30 pigtail
16AWG bare leads
red lead
black lead
Wago distribution
Two Wago 222-413 connectors
positive splitter
ground splitter
35kg servo
Direct battery power plus signal
red power
black/brown ground
orange/yellow signal
LM2596 buck
Adjust output to 5.0V first
IN+ from Wago
IN- from Wago
OUT+ 5V
OUT- ground
Breadboard
Logic rails only
5V rail
PWM row
GND rail
XIAO nRF52840
PWM controller
5V/VBUS
GND
PWM pin
USB-C from computer
!
PWM through the breadboard is fine. Do not route servo red/black power through the breadboard.
Next Build Phases
Phase 1 proves the wiring and software on the desk. Phase 1.5 adds a practical two-part removable mount, then the next phases move toward a cleaner enclosure, a more universal unlocker that supports different door hardware, and eventually a cheaper product-ready design.
Phase 1.5
Two-part removable mount
Before the full enclosure, build a simple 3D printed mounting system: a Command-strip back plate that stays on the door and a removable electronics/servo sled that slides onto it. The battery should be easy to disconnect or pull for charging, while the controller, wiring, Wagos, and servo stay firmly mounted.
ADoor back plate. Wide flat plate for large removable strips, sized to resist servo torque without peeling.
BFixed sled. Controller, buck, Wagos, wiring, and servo mount stay secured to the module so repeated battery swaps do not disturb alignment.
CBattery quick disconnect. Add an XT30-accessible pocket, clip, or short pigtail so the battery can be unplugged and removed without opening up the rest of the build.
DDovetail rails. Rails or a dovetail track keep the sled tight against the plate, with a clip or thumb screw to stop accidental release.
EAdjustment slots. Servo bracket and arm position should have small alignment slots before the door-mounted geometry is finalized.
Phase 2
Integrated printed housing
After the Phase 1.5 slide-on mount works, the next enclosure should merge the sled into a cleaner, mostly vertical housing. The goal is to stay thin off the door instead of stacking thickness: solar/status LED at the top, servo and arm near the handle, controller plus Wago/service bay below that, and the removable battery at the bottom. That vertical layout should also make servicing easier because parts are not buried behind each other depth-wise.
1Thin vertical stack. Lay parts out by height instead of depth: solar/status LED, then servo/arm, then controller plus Wago/service bay, then bottom battery. Nothing should be stacked depth-wise in a way that blocks service access.
2Slide-out battery bay. Battery should sit low, slot in, click or friction-fit, and pull out quickly from the side or bottom for charging or replacement.
3Solar panel mount. Housing should reserve a top/front face for the mini solar panel and route its charging leads internally.
4Back-plate compatibility. Keep the same slide-on mount pattern so the full enclosure can reuse the Phase 1.5 door plate.
5Serviceable wiring. Prefer connectors, sockets, Wagos, or small screw terminals so battery, servo, controller, and charger can be replaced.
6Shielding-ready layout. Leave room for foil, grounded shielding, ferrites, or cable routing changes around the controller and servo leads if EMI/RFI testing shows noise issues.
AI-generated concept image. The real Phase 2 enclosure will likely be much sleeker and thinner; this is only a visual direction for the housing, battery slot, solar area, and service layout.
Phase 3
Handle-attached mount
After the simple Command strip mount works, the next mechanical upgrade is a bracket that attaches around the fixed part of the handle assembly. That should make the unit easier to move between doors and reduce reliance on adhesive strength.
AAround-handle bracket. Clamp around the fixed rose/escutcheon area when the door hardware shape allows it.
BDoor-agnostic geometry. Keep the servo position adjustable so future handle styles can be supported.
CSolder only where it helps. Permanent solder joints can improve reliability, but modular connectors may be better for upgrades and field repair.
Phase 4
Universal door support
This phase turns the project from a lever pusher into a more flexible unlocker. The bracket should still attach around a fixed part of the handle assembly, but the actuator side should support more than one unlock motion. A small vision system can help the unit understand handle/lock geometry, guide placement, and eventually make better inside/outside presence decisions for auto-unlock.
AMultiple actuator modes. Push a lever down, rotate a thumbturn/turnpiece, press a privacy button, or drive a future handle-mounted module.
BMore universal geometry. Adjustable arms, offsets, and contact tips should fit more door hardware without custom parts for every door.
CDual-camera vision setup. Explore one forward-facing camera for handle/turnpiece/button geometry and one inward-facing room-side camera for inside approach context, so future versions can tell whether auto-unlock should happen when someone is actually near the door from inside.
DLower-cost BOM pass. Keep the prototype flexible, but start replacing expensive one-off parts with cheaper equivalents where reliability is not hurt.
Phase 5
Sellable product version
Phase 5 is where the design moves from a project to something that could be sold. The focus shifts toward repeatable assembly, cheaper custom parts, reliability testing, tamper-resistant interior hardware, water-resistant construction, battery/fire safety, interference shielding, and a clean install experience.
ACustom low-cost parts. Replace bulky prototype hardware with purpose-built brackets, actuator tips, and enclosure pieces.
BProduction electronics. Move toward a cleaner board, smaller wiring harness, better battery monitoring, and fewer hand-assembled connections.
CReady-to-install package. Include the mount, battery, charging path, setup flow, safety limits, and clear compatibility guidance.
DInterior tamper resistance. Cover wiring, add strain relief, hide casual-access fasteners, and enclose moving parts while keeping owner service access possible.
EWater and thermal safety. Add splash/humidity protection, drainage or sealing where needed, flame-retardant material choices, fusing, and protected battery charging.
FInterference shielding validation. Add EMI/RFI shielding, cleaner cable routing, filtered power paths, and real-world shielding validation so wireless control, sensors, and future accessories stay reliable in noisy apartments.
GVision setup hardening. If the Phase 4 dual-camera setup works, refine privacy controls, lens placement, lighting tolerance, offline calibration, and failure recovery so vision helps installation and presence context without becoming a constant recording feature.
Phase 6+
Cost, quality, design, and R&D
Later phases are about owning more of the system, lowering cost, increasing quality, and polishing the parts that matter most: industrial design, thinness, power use, mechanical reliability, app experience, manufacturing, advanced batteries, high-efficiency solar, removable door swing add-ons, integrated door concepts, and future access-control integrations.
AOwn the core modules. Custom actuator, power, battery, charging, and enclosure systems can reduce cost, improve quality, and make the product thinner.
BReliability lab work. Measure cycle life, battery drain, solar recovery, water ingress, thermal faults, stall behavior, adhesive/bracket load, and door-to-door compatibility.
CFuture integrations. Explore deeper platform support such as Matter, HomeKit-style control, UWB-assisted presence, and richer diagnostics.
DIndustrial design polish. Refine the look, reduce thickness, hide bulk, improve material finish, and make the mounted unit feel sleeker and more intentional.
EDoor swing add-on. Design and build our own easily removable companion add-on that pairs with the unlocker to automatically open and close common doors using an innovative, quick-install mechanism such as controlled magnetic assist, with force limits, obstacle detection, and manual override.
FIntegrated door platform. Explore a future installable door system with the unlocker and swing motion built in, using innovative hardware such as magnetic-hinge concepts to reduce noise, creaks, and visible bulk.
GAdvanced power stack. Evaluate solid-state battery options, higher-efficiency solar cells, better charge management, and energy-harvesting layouts once the product design is mature enough to justify custom power hardware.
HExterior doorbell face-recognition add-on. Explore a separate weather-resistant outside module with a doorbell button, camera, face recognition, privacy controls, and secure handoff to the interior unlocker.
Phase 2 CAD Fit Model
This is the first print-oriented pass: a parametric enclosure source plus a color-coded fit preview. The model lays parts out vertically so the shell stays thin and serviceable instead of hiding components behind each other depth-wise.
Shell envelope
First-pass tall housing with 3mm walls, rounded top/corners, service openings, and a separate back plate.
78 W x 37 D x 352 HFirst-pass tall housing with 3mm walls, rounded top/corners, service openings, and a separate back plate.
Solar placeholder
Reserved top panel space. Exact solar panel can change before printing.
50 W x 3 D x 80 HReserved top panel space. Exact solar panel can change before printing.
Servo bay
Holds the INJORA 35kg servo block, arm clearance, cable exit, and screw access.
62 W x 31 D x 62 HHolds the INJORA 35kg servo block, arm clearance, cable exit, and screw access.
XIAO controller
Includes a Seeed XIAO nRF52840 Sense footprint plus pre-soldered header/USB-C clearance.
17.8 W x 11 D x 21 HIncludes a Seeed XIAO nRF52840 Sense footprint plus pre-soldered header/USB-C clearance.
Wago pair
Modeled as two accessible 222-413 connector blocks in the service bay.
2 x 17 W x 20.5 D x 14.5 HModeled as two accessible 222-413 connector blocks in the service bay.
Current buck module
Bulky LM2596 prototype bay. This can shrink later with the low-quiescent regulator plan.
60 W x 12 D x 40 HBulky LM2596 prototype bay. This can shrink later with the low-quiescent regulator plan.
Battery cartridge
Vertical bottom-inserting pack, mostly inside the enclosure with only a small pull lip exposed.
43 W x 22 D x 75 HVertical bottom-inserting pack, mostly inside the enclosure with only a small pull lip exposed.