# Stapler Feedback Prototype

# Module 3 Activity 1 Research

### Discrete staple sensing with NeoPixel feedback

#### by Rajatpal & Jesse

Overview

# Project 3 Weekly Update

We reimagined the stapler-monitoring prototype to fit entirely inside a larger stapler body, using an ESP8266 Huzzah, a Hall effect sensor, and a NeoPixel LED to signal staple presence and trigger events. This section documents the research and build steps for Activity 1.

## Activity 1: Fabricating a Discreet Stapler Indicator

Our goal was to make a stapler that gives visual feedback when staples are present or when the stapler has been fired. A Hall effect sensor detects the magnet on the magazine pusher, a NeoPixel LED changes colour to reflect state, and the whole system is controlled by an ESP8266 Feather Huzzah with LiPo power for future mobility.

### What We Wanted to Build

A discreet, internally housed sensor that signals staple availability so users no longer have to guess whether the stapler is empty or jammed. The NeoPixel was intended to provide simple green/yellow feedback based on the Hall sensor trigger.

### Purpose

Deliver immediate visual confirmation of staple status, removing the need to open the stapler or rely on guesswork during fast-paced work.

### Preparing our Components

We moved to a larger stapler, slid additional cavities to house the magnet and sensor, and cut the Hall sensor from its PCB to extend it with soldered wires. The sensor now sits in a discreet metal cavity near the staple mechanism, while a second opening near the back hints at a future “LOADED” indicator. The NeoPixel was soldered to wires, ready to mount through a drilled aperture, and the ESP8266 with LiPo battery forms the controller/power combination.

### Documented Progress

Photos from the Activity 1 build show the sensor routing, NeoPixel placement, and wiring that ties the Hall effect sensor to the Feather controller.

ESP8266 Feather board that drives the Hall sensor and NeoPixel.

Preparing red and black leads with helping hands before soldering extensions.

Finished solder joint connecting the red extension wire to a black lead.

Stapler disassembled: carriage, plastic body with spring, and hardware laid out.

Top-down layout of stapler parts: track with spring, shell, loose spring, and steel rail.

Hall effect sensor breakout with the detached 3144 sensor ready for rewiring.

## Prototyping

Assembling our new prototype meant relocating the magnet and Hall sensor inside the stapler, threading wiring past the spring, and proving the interaction loop with the ESP8266 and NeoPixel.

We first placed the magnet on top of the magazine pusher (same as the earlier prototype), then carefully trial-fit the Hall sensor so it could read the magnet while keeping wiring clear of the spring. Multiple attempts were needed to tuck the leads neatly. We drilled a side hole for the NeoPixel LED (pre-soldered) and retested sensor + magnet with simple code to confirm placement.

With hardware assembled, we wrote code so the Hall trigger would toggle the NeoPixel between green and yellow—single-input logic that lets us reset the LED without reprogramming. A broken battery connector prevented a fully wireless demo, so tests remained USB-powered.

### Part 1: Assembly and Wiring (@WEEK2P3)

We broke down the stapler, extended sensor and LED leads, and tested wiring paths before reassembly.

Stapler opened into carriage, shell, and magazine strip for sensor placement.

Top-down layout of carriage, shell, and magazine strip pre-wiring.

Helping hands position stripped leads before soldering Hall sensor extensions.

Soldering Hall sensor extension wires with helping hands.

Close-up of the finished solder joint on Hall sensor extensions.

Hall sensor extension harness with heat-shrink and coil spring.

Hall sensor harness routed inside the shell with strain relief.

Carriage reassembled showing the magazine spring path.

Magazine rail wired out to the ESP8266 for bench testing.

Lead bundle exits the rail and connects to the ESP8266.

### Part 2: Integrated Test Fit (@WEEK3P3)

With wiring proven, we test-fit the harness through the stapler body, powered by the ESP8266, to verify sensor response and strain relief.

Heat-shrunk lead bundle exiting the rail during live test.

Rear cavity view with spring-wrapped harness seated.

Rear view of the stapler wired to the ESP8266 for testing.

Closed stapler tethered to the ESP8266 during validation.

Top-down view of the rail and spring with harness connected.

Front view of the closed stapler during bench testing.

## Final Prototype

Current Prototype

Unfortunately we broke our connector to our battery at the last minute so we were unable to achieve a true wireless setup from our computer.

At this stage, our prototype successfully demonstrates the core functionality of our concept. The sensor detects the magnet when the stapler is pressed, and the NeoPixel LED reliably changes colour in response when powered through Arduino. The sensor placement is far more discreet than before, keeping sensing components inside the stapler body. We now demo on Arduino because the Feather–NeoPixel pairing was too unstable.

NeoPixel lit blue while tethered to the ESP8266 on bench power.

Top-down interior wired to Arduino Uno for stable power/logic.

Highlighted Hall sensor and NeoPixel LED placement inside the stapler.

Green indicator lit while tethered to the Arduino.

### What’s Working

- The Hall sensor, once extended and soldered, accurately detects the magazine pusher magnet.
- The NeoPixel LED toggles correctly between two colours based on sensor activation.
- Sensor placement inside the metal cavity is hidden and reliable; wiring is cleaner than the first prototype.
- Core colour-based feedback logic is stable and reproducible on Arduino power.

### What’s Not Working

- Wireless setup is blocked by the damaged JST battery connector.
- Feather/NeoPixel proved unstable without solid grounding and an inline resistor.
- Single sensor limits us to binary “staple/no-staple” feedback—no level granularity yet.
- ESP32 and battery remain external, limiting portability; magazine pusher is weakened.
- Feather board produced unpredictable NeoPixel behaviour, so Arduino is used for demos.

### Troubleshooting Summary

Grounding inconsistencies on the ESP32 caused random NeoPixel colours; adding a data-line resistor and unified ground fixed this. The broken battery connector blocked wireless testing. Sensor placement required multiple fit/adjust/retest cycles to avoid the internal spring. Arduino delivered consistent results, so we rely on it for demonstrations.

Blue indicator test using a breadboard resistor inline.

### Next Steps / Fix Plan

- Repair/replace the JST battery connector to restore wireless operation.
- Solder a permanent inline resistor on the NeoPixel data line for stability.

### Future Prototype

After stabilizing Huzzah–NeoPixel compatibility and adding the battery, two major upgrades follow:

- Add a second Hall sensor at the back of the magazine for multi-state staple levels (bright green full, lighter green “full-ish,” yellow low).
- Design and 3D print housing to enclose ESP32 and battery inside the stapler for better ergonomics and safety.
- Refine internal wiring to avoid spring interference and improve durability.
- Begin a medical-grade version suited to surgical staplers and sterilization needs.

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