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TELEGRAHAM TESTED SENTINELAPEX SENTINEL PROJECT
Free software · Waitlist now open

Meet Apex Sentinel.

Apex can leave additional alarm conditions without a new notification while an earlier alarm is awaiting acknowledgment. Apex Sentinel independently monitors alarm states and can send its own notifications. The software is free; you supply the ESP32 hardware.

Illustration of Apex Sentinel monitoring alarms and sending notifications
Important: the black Sentinel box in the illustration is a visual mockup only. No finished black enclosure or preassembled Sentinel device is included or sold. You must purchase your own compatible ESP32 board. An ESP32 hardware option is linked below; software will be provided free when released.
View an ESP32 hardware option on Amazon ↗

Join the waitlist

Leave your email and I'll let you know when Apex Sentinel is ready to download. No purchase or payment required to join.

Your email will be used only for Apex Sentinel release updates. This form does not place a hardware order.

Supported hardware

The planned 1.9.0 release supports ESP32 development boards, M5Stack Core2, and the original LILYGO T-Display. You supply the hardware; Apex Sentinel software will be free when released.

A simple board. Independent alarms.

ESP32ESP32-S3ESP32-C3ESP32-C6

A compatible development board with at least 4 MB of flash, a data-capable USB cable, and a USB power supply, plus 2.4 GHz WiFi and a reachable Neptune Apex controller, are needed to get started.

Set up WiFi, Apex connections, and notifications in your browser. Add an optional buzzer or relay if you want a local audible alarm.

See an ESP32 hardware option ↗
More information, right at the tank

If you decide to move up to the Core2, these features improve your Apex Sentinel experience.

M5Stack Core2

Supported Core2 revisions: V1.0 and V1.1/V1.3. Select the Core2 build in the installer.

  • A screen at a glance. See whether everything is OK, active alarms, and monitored readings.
  • Touch controls. Acknowledge alarms, change screens, and adjust brightness on the device.
  • Sound and vibration. Enable the built-in speaker and vibration for local alerts.
  • Battery backup. Keep running when USB power is lost, with a power-cut alarm.

To detect tank power loss, plug the Core2’s USB supply into the same circuit as the tank. Remote power-cut notifications still need a working network; a UPS for your router and modem can keep that path available.

View M5Stack Core2 on Amazon ↗
Compact screen and two buttons

Original LILYGO T-Display

The original ESP32 model with a 1.14-inch, 240 × 135 color screen and 4 or 16 MB flash will have its own build.

  • A complete Sentinel. The screen adds alarm status, readings, network details, and setup QR codes.
  • Simple buttons. Acknowledge alarms, change screens, and dim the display.
  • Optional local sound. Add an external buzzer or relay if needed.

No built-in speaker or vibration, and no Core2-style USB power-cut detection. T-Display-S3 is a different model; this display build is for the original ESP32 board.

What your setup needs

A reachable Neptune Apex

Sentinel reads the Apex’s local status API and monitors up to four controllers. Watch readings, leak/float switches, outlet power, and output states. It does not change Apex settings or control equipment. Local API compatibility depends on your Apex firmware and network setup.

A browser for setup

Install by USB using Chrome or Edge on a computer. Configure WiFi, Apex connections, and alarms in the browser walkthrough. After setup, Sentinel runs on its board; a computer does not need to stay on for alarm monitoring.

Optional viewing away from home

The planned release includes a read-only live view. Tailscale remote access needs a separate always-on home device, such as Home Assistant, a Raspberry Pi, or a PC. Use a reserved device IP and your actual home subnet. Never port-forward Sentinel. Alerts work without Tailscale.

Choose Pushover, ntfy, Telegram, Discord, Slack, Gotify, a webhook, MQTT/Home Assistant, or a local buzzer/relay. Third-party services may require an account or have fees. Sentinel shows current readings, with no long-term graphs or history. Keep your existing aquarium protections and test the whole alert path.

Apex Sentinel setup: 1, 2, 3.

Here’s how you’ll get started when the software is released.

Install on your board

Connect it by USB, then open the browser-based installer in Chrome or Edge on a computer. The installer detects the chip; for a classic ESP32, choose generic ESP32, M5Stack Core2, or original T-Display. A first installation erases the board.

Connect WiFi and Apex

Restart the board, join its ApexSentinel-xxxx setup network, and follow the browser walkthrough to connect to your home WiFi and find your Apex.

Choose and test your alerts

Set your alarm conditions and notification channels. Send a test notification and safely test an alarm so you know the whole path works.