Handheld Force-Sensing Probe Development
Budget: $10 – $30 USD
# Prototype Brief — Handheld Force-Sensing Probe
## Summary
I need a working prototype of a small handheld instrument that measures the contact force applied through a thin rigid probing tip. When the tip is pressed against a surface, the device reads the applied force in real time and signals when a target force is reached. All sensing and electronics stay inside the handle; the tip itself is a slim passive pin.
This is a proof-of-concept prototype, not a finished product. Priority is a fast, cheap, working demonstration.
## How it works (concept)
- A thin, rigid probing tip is mounted on a shaft.
- The shaft is free to slide a tiny amount (roughly 0.1–0.3 mm) inside the handle against a light preload spring.
- Pressing the tip transfers axial force to a force sensor housed in the handle.
- The electronics read the force, show it live, and trigger feedback (light + vibration) when a configurable target force is reached.
- Force readings are also sent wirelessly (Bluetooth) to a phone/tablet or PC.
The key design rule: **the part that touches the surface stays thin and passive; all sensing lives in the handle.**
## Functional requirements
- Measure axial contact force through the tip, in roughly the 0.05–1.0 N range, with a configurable alert threshold set in firmware.
- Live force value available over Bluetooth (BLE).
- On-device feedback: an LED (e.g. green below threshold, red above) and a small vibration cue at the threshold.
- Handle is sealed enough to survive wipe-down cleaning with disinfectant (no full waterproofing / autoclave needed).
- Tip + shaft are removable stainless steel and contain no wiring.
## Form factor
- Handle roughly pen-sized (about 12–16 mm diameter), balanced so it feels like a normal handheld instrument.
- Tip stays slim (comparable to a fine probe pin).
- Total length and weight kept close to a standard handheld probe.
## Suggested starting components (open to substitution)
- Force sensor: small MEMS force sensor or micro compression/button load cell.
- Signal conditioning: HX711 or ADS1220 ADC.
- Controller with wireless: Seeed Xiao ESP32-C3 or nRF52840 (BLE).
- Power: small rechargeable LiPo (100–150 mAh) with onboard charging.
- Feedback: RGB LED + small coin vibration motor.
## Deliverables
1. Working prototype: probing tip + sliding shaft + force sensor + electronics inside a 3D-printed handle.
2. Firmware: reads force, converts to real units, drives the LED + vibration threshold, streams force over BLE.
3. Calibration: force reading validated against known weights, with the method documented.
4. Simple readout: a basic phone/PC display of the live force value (a minimal app or existing BLE viewer is fine).
5. Source files: firmware code, CAD files for the shaft/handle, wiring diagram, and a short build/calibration note.
## Skills needed (ideally one person)
- Embedded electronics + firmware (load cell / ADC / microcontroller, BLE).
- Mechanical design / CAD + 3D printing (the sliding-shaft mechanism and sealed handle).
- A mechatronics or hardware-prototyping generalist is the ideal fit.
## To include in your proposal
- Similar hardware prototypes you've built (with photos/links if possible).
- Whether you can handle both the electronics and the mechanical/CAD side, or only one.
- Rough cost and timeline to a working prototype.
- Any parts you'd recommend changing and why.
## Terms
- An NDA will be signed before detailed discussion.
- All designs, code, and IP created for this project are assigned to me.
## Summary
I need a working prototype of a small handheld instrument that measures the contact force applied through a thin rigid probing tip. When the tip is pressed against a surface, the device reads the applied force in real time and signals when a target force is reached. All sensing and electronics stay inside the handle; the tip itself is a slim passive pin.
This is a proof-of-concept prototype, not a finished product. Priority is a fast, cheap, working demonstration.
## How it works (concept)
- A thin, rigid probing tip is mounted on a shaft.
- The shaft is free to slide a tiny amount (roughly 0.1–0.3 mm) inside the handle against a light preload spring.
- Pressing the tip transfers axial force to a force sensor housed in the handle.
- The electronics read the force, show it live, and trigger feedback (light + vibration) when a configurable target force is reached.
- Force readings are also sent wirelessly (Bluetooth) to a phone/tablet or PC.
The key design rule: **the part that touches the surface stays thin and passive; all sensing lives in the handle.**
## Functional requirements
- Measure axial contact force through the tip, in roughly the 0.05–1.0 N range, with a configurable alert threshold set in firmware.
- Live force value available over Bluetooth (BLE).
- On-device feedback: an LED (e.g. green below threshold, red above) and a small vibration cue at the threshold.
- Handle is sealed enough to survive wipe-down cleaning with disinfectant (no full waterproofing / autoclave needed).
- Tip + shaft are removable stainless steel and contain no wiring.
## Form factor
- Handle roughly pen-sized (about 12–16 mm diameter), balanced so it feels like a normal handheld instrument.
- Tip stays slim (comparable to a fine probe pin).
- Total length and weight kept close to a standard handheld probe.
## Suggested starting components (open to substitution)
- Force sensor: small MEMS force sensor or micro compression/button load cell.
- Signal conditioning: HX711 or ADS1220 ADC.
- Controller with wireless: Seeed Xiao ESP32-C3 or nRF52840 (BLE).
- Power: small rechargeable LiPo (100–150 mAh) with onboard charging.
- Feedback: RGB LED + small coin vibration motor.
## Deliverables
1. Working prototype: probing tip + sliding shaft + force sensor + electronics inside a 3D-printed handle.
2. Firmware: reads force, converts to real units, drives the LED + vibration threshold, streams force over BLE.
3. Calibration: force reading validated against known weights, with the method documented.
4. Simple readout: a basic phone/PC display of the live force value (a minimal app or existing BLE viewer is fine).
5. Source files: firmware code, CAD files for the shaft/handle, wiring diagram, and a short build/calibration note.
## Skills needed (ideally one person)
- Embedded electronics + firmware (load cell / ADC / microcontroller, BLE).
- Mechanical design / CAD + 3D printing (the sliding-shaft mechanism and sealed handle).
- A mechatronics or hardware-prototyping generalist is the ideal fit.
## To include in your proposal
- Similar hardware prototypes you've built (with photos/links if possible).
- Whether you can handle both the electronics and the mechanical/CAD side, or only one.
- Rough cost and timeline to a working prototype.
- Any parts you'd recommend changing and why.
## Terms
- An NDA will be signed before detailed discussion.
- All designs, code, and IP created for this project are assigned to me.