# How to make an ESP32, Arduino or Raspberry Pi ring your phone

Builders · https://lfg.gm/maker-projects-phone-alarm · Updated 2026-10-19

To make an ESP32, an Arduino with Wi-Fi or a Raspberry Pi ring your phone, have it send one HTTP POST to the private link of an anything alarm in LFG Alarm. LFG Alarm is a social alarm clock for iPhone and Android, and lfg.gm in a desktop browser. The board notices something (a door left open, water on the floor, a print finished) and the request rings your phone like an alarm, plus the phones of anyone you shared the alarm with. No library, no account on the device, no key: the link is the whole integration.

## Before you start

- **The LFG Alarm app on your phone**, signed in. Your board sends the request; the app is what rings.
- **A board on Wi-Fi**: an ESP32, an Arduino with Wi-Fi (such as an Uno R4 WiFi or a Nano 33 IoT), or a Raspberry Pi. It needs to reach the internet over HTTPS.
- **An anything alarm.** In the app, on **Alarms**, tap **🔮 Anything**, pick a **Cooldown**, keep it private or share it with friends, and tap **Arm it**. Copy the link from the link card. More on how the link works: [How to make any app, script or feed ring your phone](https://lfg.gm/webhook-alarm).

The link looks like `https://api.lfg.gm/horn/<token>`. Treat it like a password: anyone who has it can ring the alarm. Keep it out of public repositories (a `secrets.h` or an environment variable you do not commit), and tap **New URL** on the alarm's page if it leaks.

## The code

Each snippet sends an empty POST. LFG Alarm ignores the body, so there is nothing to format.

**ESP32 with MicroPython**

```python
import network, urequests, time

RING_URL = "https://api.lfg.gm/horn/your-token"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect("your-wifi", "your-wifi-password")
while not wlan.isconnected():
    time.sleep(0.5)

def ring():
    r = urequests.post(RING_URL)
    print(r.status_code)  # 200 rang, 429 in quiet time, 409 switched off
    r.close()
```

**ESP32 or Arduino with the Arduino core**

```cpp
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>

const char* RING_URL = "https://api.lfg.gm/horn/your-token";

void ring() {
  WiFiClientSecure client;
  client.setInsecure();  // skips certificate checks; fine for a ring
  HTTPClient http;
  http.begin(client, RING_URL);
  int code = http.POST("");
  Serial.println(code);
  http.end();
}
```

Call `WiFi.begin(...)` in `setup()` first. Other Wi-Fi boards use their own libraries (for example `WiFiS3.h` with `ArduinoHttpClient` on an Uno R4 WiFi); the request is the same empty POST over HTTPS.

**Raspberry Pi with Python**

```python
import requests
requests.post("https://api.lfg.gm/horn/your-token", timeout=10)
```

**Raspberry Pi with curl**, for a shell script or a cron job:

```bash
curl -s -X POST "$LFG_RING_URL"
```

Call `ring()` when your condition turns true, not on every loop. After a ring, the alarm stays quiet for its Cooldown (1 minute to 1 hour), so a sensor that flickers rings once, but keeping your own "already rang" flag means fewer wasted requests.

## Ideas that earn a ring

**Door left open.** Lena's back gate has a reed switch on an ESP32. If it stays open for ten minutes after 22:00, the board rings an alarm called "Gate open". A one hour Cooldown means one ring per night, not one per minute.

**Fridge, freezer or leak.** Theo's chest freezer in the garage has a temperature probe on a Pi. Above minus 10 degrees for half an hour, it rings him and his partner. A water sensor under the washing machine does the same for a leak, and rings the whole house.

**3D print finished.** Sam starts eight hour prints at night and wants to pull the part before it cools onto the bed. Two ways to do it with no code:

- **OctoPrint:** the **OctoPrint-Webhooks** plugin calls a URL on events such as **Print Done** and **Print Failed**. Paste the link, set the HTTP method to POST, and tick the events you want.
- **Klipper with Moonraker:** add a `[notifier]` section to `moonraker.conf`. Moonraker sends notifications through Apprise, whose `jsons://` address makes an HTTPS POST:

```ini
[notifier print_done]
url: jsons://api.lfg.gm/horn/your-token
events: complete, error
```

Restart Moonraker after editing. Check the current Moonraker and Apprise docs if your version differs.

**Plant dry.** Priya's greenhouse has a soil moisture sensor on an ESP32. A dry plant is rarely a 3am emergency, so she makes the alarm private and lets the board ring only between 08:00 and 20:00. For things that can wait, a ring is too much; use it for the ones that cannot.

**Your robot can wake you.** Jun's rover patrols the shed on a Pi. When its battery runs low or it gets stuck, it rings "Rover needs you". A robot that can ring a phone is also a fine alarm clock: his rings him at sunrise on build days.

## Running Home Assistant already?

If your sensors already report to Home Assistant, let it do the ringing with a `rest_command` instead of adding code to each board. See [Ring your phone from Home Assistant](https://lfg.gm/agents/home-assistant).

## How it rings

On Android an anything alarm rings full screen like an alarm. On iPhone it arrives as a time-sensitive alert with the alarm's sound, so the ringer should be on. Everyone who joined the alarm is rung at once. LFG Alarm is not a monitored safety service: keep real smoke and CO alarms, and emergency numbers.

## If it does not work

- **Status 200 but no ring:** check the app is signed in on your phone, and on iPhone that the ringer is on.
- **Status 429:** the alarm is in its Cooldown after a recent ring. Wait, or use a shorter Cooldown while testing.
- **Status 409:** the alarm is switched off. Turn it on in the app.
- **Status 404:** the token is wrong, or you made a **New URL** and the board still has the old one.
- **A negative status or a TLS error on an ESP32:** the board could not open the HTTPS connection. Check Wi-Fi, the clock (some TLS setups need the time set), and that you used `WiFiClientSecure`.
- **Nothing happens when you open the link in a browser:** that is a GET, which does nothing. Use POST, or **Test fire** in the app.

## Questions

### Does the board need my LFG Alarm sign-in?
No. Only the link. It never sees your account.

### Can one sensor ring several people?
Yes. Share the anything alarm with them as a friends alarm. Anything alarms are private or friends, never public.

### Can I tell which sensor rang?
Give each sensor its own anything alarm with a clear name and its own sound. Whatever you put in the request body is not shown.

## Learn more

- [How to make any app, script or feed ring your phone](https://lfg.gm/webhook-alarm)
- [Ring your phone from Home Assistant](https://lfg.gm/agents/home-assistant)
- [The fastest way to get your whole family's attention](https://lfg.gm/family-alert)
- [Anything alarms](https://lfg.gm/wiki/anything-alarms) and [friends and groups](https://lfg.gm/wiki/friends-and-groups)

## Sources and further reading

- [MicroPython: network basics on the ESP32](https://docs.micropython.org/en/latest/esp32/quickref.html#networking)
- [Arduino ESP32: HTTPClient](https://github.com/espressif/arduino-esp32/tree/master/libraries/HTTPClient)
- [Python Requests: quickstart](https://requests.readthedocs.io/en/latest/user/quickstart/)
- [OctoPrint plugin: Webhooks](https://plugins.octoprint.org/plugins/webhooks/)
- [Moonraker: configuration, notifier](https://moonraker.readthedocs.io/en/latest/configuration/)
- [Apprise: custom JSON notifications](https://github.com/caronc/apprise/wiki/Notify_Custom_JSON)

LFG Alarm is not affiliated with Espressif, Arduino, Raspberry Pi, OctoPrint, Klipper, Moonraker or Apprise.

## Keep exploring

- [Website change alerts: how to get an alarm when something happens online](https://lfg.gm/alert-when-something-happens-online.md): Point a website change monitor, an uptime monitor, Zapier, IFTTT, GitHub Actions or a cron script at an anything alarm’s link and it rings your phone.
- [How to make any app, script or feed ring your phone](https://lfg.gm/webhook-alarm.md): An anything alarm is a private link that rings you, and your friends, whenever something calls it.
- [How to make Zapier ring your phone](https://lfg.gm/zapier-phone-alarm.md): End a Zap with a Webhooks by Zapier POST to an anything alarm's link, add a filter, and only what matters rings you and your team.
- [How to make a Make scenario ring your phone](https://lfg.gm/make-phone-alarm.md): Add the HTTP Make a request module with POST to an anything alarm's link, filter the line before it, and only what matters rings.
- [How to make IFTTT ring your phone](https://lfg.gm/ifttt-phone-alarm.md): Point IFTTT's Webhooks Make a web request action at an anything alarm's link, and see how it compares with IFTTT's own phone call.
- [Phone alarms for founders and solo developers](https://lfg.gm/alerts-for-founders.md): Ring your phone when the site goes down, a deploy finishes, the first sale lands or signups spike, and wake the team together on launch day.

## About LFG Alarm

LFG Alarm is a social alarm clock for iPhone, iPad and Android. It rings for times and for moments (a post on X, a stream going live, a token price, a wallet buying, an event starting), and one shared link makes every phone that joined ring together. Rocco, the cat inside the app, keeps watch and wakes you up.

- Get it on Google Play: https://play.google.com/store/apps/details?id=gm.lfg.app
- Download on the App Store: https://apps.apple.com/app/id6821089085
- Use it from an AI agent: add the MCP server https://mcp.lfg.gm as a connector, then ask in plain words.
- Every page for agents: https://lfg.gm/llms.txt