Swing Box — IoT Gym Equipment Security
From spec to BOM to CAD — full hardware PM package for a connected gym equipment security enclosure.
0 Risks
Assessed in Risk Matrix
0-Day
Battery Life Target
0× Load Cells
Per Enclosure for Weight Detection
Tech Stack
The Challenge
Swing Fitness operated a shared-use gym equipment rental model — dumbbells and kettlebells deployed at commercial and residential sites. Without a connected security layer, equipment was frequently misplaced, removed without authorisation, or left at incorrect locations with no visibility for operators. The Swing Box needed to solve three problems simultaneously: detect exactly which weights were removed from the enclosure (load cell weight counting), alert operators if equipment left a defined geo-fence (GPS tracking), and allow authorised lock/unlock from a mobile app (solenoid actuation) — all while running on battery for at least 60 days to avoid frequent servicing, and surviving a gym environment (waterproofing, temperature extremes, mechanical latch durability under repeated use).
Product Requirements Document
PRODUCT SPECIFICATION
Swing Box — Connected Gym Equipment Security
Varun Cumbanungam · Product Manager · Renovatto (2023)
Doc ID
SWNG-SPEC-V1
Status
Approved
Owner
Varun C.
Date
2023
Version
1.0
Problem Statement
Shared gym equipment is frequently misplaced without authorisation. Swing Box must detect weight removal, trigger geo-fence alerts, enable lock/unlock via app, and run 60 days on battery.
Primary Users
Gym Operator
Fleet overview, geo-fence config, theft alerts
Site Manager
Lock/unlock via app, item count monitoring
Field Technician
Installation, calibration, battery replacement
End User
Transparent — unaware of device presence
Core Subsystems
- 4× TE Connectivity FX19 load cells (100 lbf each)
- 12V RS PRO latching solenoid (16×14×30mm)
- GPS geofencing — home location + BLE wake
- 60-day battery target — GPS polling + BLE wake
- Mobile app — lock/unlock, item count, alerts
Key Acceptance Criteria
- AC-1Weight removal detected within 2s of lift-off
- AC-2Geo-fence breach alert within 30s of crossing
- AC-3Lock/unlock command executed within 3s
- AC-4Battery ≥60 days standby with daily GPS poll
- AC-5IP rating test — no ingress failure
- AC-6Load cell false-positive rate <2% calibrated
Risk Assessment
- HIGH
GPS not working correctly indoors
Last-known location fallback + fault tolerance spec
- HIGH
Missing weights not detected — miscalibration
4-cell redundant arrangement + recalibration
- HIGH
Device not waterproof — gym conditions
Mechanical redesign to meet IP67
- MED
Battery life <60 days
Increase capacity or reduce GPS poll frequency
Product Artefacts Delivered
- Product Spec V1 — subsystem specs, ACs, constraints
- BOM — 80 load cells, 20 solenoids, 20-unit pilot
- CAD enclosure review — solenoid fit, IP seal
- Risk Assessment Matrix — 18 identified risks
CONFIDENTIAL · Swing Box Product Spec · Property of Renovatto
Product Spec · BOM · CAD Review · Risk Assessment (18 risks)
Full PRD and supporting artefacts available upon request
System Design & Specification
Ruggedized enclosure with weight-sensing load cells to detect item removal. Integrated GPS geofencing alerts operators if equipment moves beyond authorized boundaries. Remote electronic lock enables staff control via mobile app. Power system engineered for extended battery life (60+ days) to minimize maintenance frequency.
The product specification defined four functional subsystems. Weight detection: four compression load cells (TE Connectivity FX19 series, 100 lbf each) counted item removal by threshold — the risk matrix identified false positives from load cell miscalibration as a high-risk item, mitigated by a 4-cell redundant arrangement and periodic recalibration. Lock/unlock: a 12V latching solenoid (RS PRO, 16×14×30 mm) controlled by the MCU received lock and unlock commands from the mobile app over the cellular/BLE data pipeline; the mechanical latch design was flagged as a high-risk failure mode requiring redesign validation. GPS / geofencing: a GPS module logged home location and triggered breach alerts when the enclosure moved beyond the configured geo-fence radius; GPS chip reliability in dense indoor environments was noted as a risk requiring mitigation. Battery system: sized for 60-day standby with periodic GPS polling and BLE command wake — risk assessment flagged thermal runaway potential in varying climate conditions, requiring component operating-temperature validation. The electromechanical BOM covered 80 load cells, 20 solenoids, and micro limit switches for a 20-unit pilot deployment.
Risk Assessment (excerpt)
Selected risk entries from the Swing Box risk assessment matrix — severity × likelihood → impact.
// Swing Box — Risk Assessment Matrix (excerpt)
// Severity × Likelihood → Impact | Action required
// RISK-03 Home location (GPS) not working correctly
// Severity: Generally unacceptable | Likelihood: Not likely | Impact: HIGH
// Action: Check GPS chip for faults and errors
// RISK-07 Missing weights not detected correctly
// Severity: Generally unacceptable | Likelihood: Not likely | Impact: HIGH
// Action: Check load cell calibration
// RISK-13 Device not waterproof — failure when submerged
// Severity: Generally unacceptable | Likelihood: Probable | Impact: HIGH
// Action: Mechanical redesign to meet waterproofing standards
// RISK-14 Item removal counter incorrect (4 load cells)
// Severity: Generally unacceptable | Likelihood: Probable | Impact: HIGH
// Action: Verify if 4-load-cell arrangement is sufficient
// RISK-01 Battery life < 60 days
// Severity: Tolerable | Likelihood: Probable | Impact: MEDIUM
// Action: Increase battery size or reduce firmware functionality
// RISK-12 Battery heating under climate extremes
// Severity: Generally unacceptable | Likelihood: Not likely | Impact: HIGH
// Action: Verify component operating temperature rangeResults
Delivered the complete pre-engineering product package to Swing Fitness: system specification defining all functional requirements (weight detection, lock/unlock, GPS geofencing, LED status, app command flow), electromechanical BOM for a 20-unit pilot (TE Connectivity FX19 load cells, RS PRO solenoids), STEP enclosure CAD model, system block diagram, and an 18-risk assessment matrix with mitigation actions. The package constituted the full engineering handoff document — ready for an embedded hardware team to begin PCB design and firmware development without requiring further requirements elicitation.
Gallery & Demos
Swing Box Closed
Weatherproof steel enclosure designed for gyms to securely store dumbbells and kettlebells with electronic lock.
Swing Box Open
Interior showing weight sensors and lock mechanism — sensors track which items are removed.
CAD Engineering Model
3D technical design showing all components and dimensions ready for manufacturing.
Click any image or video to expand · ← → keys navigate
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