Our customer needed a reliable BLE 4-channel smart relay control board for gates, barriers and on-vehicle 12 V scenarios controlled from a phone. The requirement was not a Wi-Fi “smart plug” tied to the cloud; it was an industrial unit that pairs quickly at short range, is protected by a PIN, reports channel state and can optionally echo status to a panel over RS-485.
Existing options were either limited RF remotes or hobby IoT kits that failed field voltage, EMC and access-control expectations. Operators wanted four independent relays from a phone, live status and blocked unauthorised access.
In short: “Control four relays safely from the phone; add a PIN; show status; optionally echo to the panel.”
Revan Technology treated the need as one product family: PCB + embedded firmware + mobile app. A shared BLE command/status protocol kept board and app aligned and shortened integration.
The board combines a 12 V-ready power stage, four relay outputs, status LEDs and an optional RS-485 interface. Firmware covers PIN validation, session timeout, a safe state on disconnect and per-channel command/response frames. The mobile side handles pairing, PIN entry, live channel state and a short command history.
The goal was not “open a relay from a phone”, but a repeatable, safe, maintainable smart relay control product for the field.
The board uses a 12 V vehicle/panel supply path with buck or LDO stage, reverse-polarity and transient protection. Four relay channels are driven with proper coil drivers, flyback diodes and load-side clearance rules. BLE antenna placement accounts for metal-panel proximity. An optional RS-485 transceiver with common-ground practice and TVS protection interfaces the field bus.
An ESP32-class / BLE-capable SoC exposes custom services via NimBLE or an equivalent stack. Command frames carry channel id, action (on/off/pulse), sequence and a short integrity field; the board returns real GPIO/relay state. After connect, the PIN becomes a session token; expiry forces re-auth. On link loss, policy either clears channels or applies a defined safe profile.
A Flutter mobile app manages scanning, pairing, PIN entry and live four-channel status. Pulse (momentary) actions support gate/barrier timing parameters. On RS-485, a simple status echo (channel bitmask or Modbus-like registers) can be enabled so the panel can read the last known state without an active mobile session.
After commissioning, gate and barrier control moved from scattered RF remotes into one BLE 4-channel smart relay control board and mobile UI.
This project combines Revan Technology’s PCB, embedded software and mobile strengths in one product line. If you have a similar phone-controlled relay need, we can scope it together.
For customer privacy, company and product names are not shared in this article. Images are representative and used to illustrate the functional structure.
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