● CASE STUDY · IDENTIUM TECH SOLUTIONS
RFID Deadman Switch
A water pump that only runs while the right tags are present.
OVERVIEW
A two-factor deadman switch for machinery, built on the IF9A fixed reader's GPO relays. The pump runs only while an authorization tag sits at antenna 2 AND an operator's tag is visible at antenna 1. Walk away, or take the key tag, and the pump cuts out on its own.
THE CHALLENGE
Controlling real machinery inverts the usual failure logic: a missed tag read can't leave a pump running unattended. Every failure mode (app crash, window closed, reader bridge dying, tags going stale) had to resolve to OFF.
WHAT I BUILT
- 01
A presence state machine re-evaluated every 200ms: 'armed' means the auth EPC was seen at antenna 2 within a freshness window; 'operator present' means any tag at antenna 1. Both are required to hold the ignition relay closed.
- 02
Fail-safe teardown paths. On stop, window close or bridge crash, both GPO relays are forced OFF before anything else happens, so the pump can never be stranded on.
- 03
GPO 1 drives the ignition relay, GPO 2 a status LED, over the @identium/reader SDK and the C# ModuleBridge that powers the rest of the product line.
- 04
Every state transition gets appended to a JSONL audit log: who armed it, when it ran, why it stopped.
OUTCOME
RFID leaving the dashboard and switching real machinery. Small, physical, and the demo that makes the whole stack click for clients.