Automate cold rooms and motor temperatures with Bluetooth sensors, InduQT and Claude

Updated Oct 31, 2026 · InduQT engineering team · Guide, not a customer case study

The short answer

Bluetooth sensors are the easiest sensors to fit: no wiring, a battery that lasts a year or more, and a price of US$20–50. They do not speak MQTT themselves, so a gateway listens to them and publishes their readings: free Theengs Gateway on the same Raspberry Pi as your broker, or a Shelly BLU Gateway. InduQT does not read Bluetooth directly; it reads what the gateway publishes, like any other MQTT sensor.

  • Cold room, panel or motor-housing temperature and humidity without running a cable
  • An alert when a cold room drifts warm, before the product is lost
  • Battery level, so a sensor never goes quiet unnoticed
CostUS$20–50 per sensor plus a gateway
Time30 minutes
SkillNo code
  1. What to buy
  2. Place the sensors
  3. Publish them over MQTT with Theengs Gateway
  4. Set up the MQTT broker (once per plant)
  5. Check the readings with Claude before you connect anything
  6. Wire it to InduQT
  7. What InduQT does with it

What to buy

RuuviTagabout €40

Battery Bluetooth sensor: temperature, humidity, pressure and acceleration. Rugged enough for machine housings. Maker: Ruuvi. Maker’s page

Shelly H&T Gen3 (Wi-Fi alternative, no gateway needed)about US$30

Temperature and humidity over Wi-Fi with MQTT built in. Maker: Shelly. Maker’s page

Theengs Gateway (software)free

Runs on the Raspberry Pi, decodes many brands of BLE sensor and publishes JSON to MQTT. Maker: Theengs (open source). Maker’s page

Shelly BLU Gateway Gen3 (hardware alternative)about US$25

Plug-in gateway for Shelly BLU sensors. Maker: Shelly. Maker’s page

Raspberry Pi 5 (4 GB) with power supply, case and 32 GB cardabout US$100 for the kit

Runs the MQTT broker and the InduQT bridge (skip it if you already built the gateway). Maker: Raspberry Pi. Maker’s page

Prices are typical street prices in US dollars when we wrote this, not quotes; buy from the maker or a local distributor. InduQT does not sell sensors and is not paid by any maker named here.

Safety. Battery sensors are safe to place almost anywhere, but in a hazardous (ATEX/IECEx) area only certified equipment is allowed, and that includes battery devices.

Place the sensors

  • Cold room: at the warmest point, usually near the door at product height, not in the evaporator’s air stream.
  • Motor or gearbox: on the housing with a cable tie or a magnet, away from the fan cover.
  • Electrical panel: inside, high up, where heat collects.
  • Keep each sensor within about 10–20 m of the gateway through walls; metal cold-room panels block Bluetooth, so put the gateway or a second one close to the door.

Publish them over MQTT with Theengs Gateway

Theengs Gateway runs on the Raspberry Pi’s built-in Bluetooth and publishes each sensor it hears to <publish topic>/<sensor id>, as JSON with decoded fields such as tempc, hum and batt.

Install and start Theengs Gateway
# On the same Raspberry Pi as Mosquitto (it has Bluetooth built in)
python3 -m venv ~/theengs && source ~/theengs/bin/activate
pip install TheengsGateway

python3 -m TheengsGateway -H localhost -P 1883 -u sensors -pw 'sensors-password' \
  -pt factory/coldroom-1 -st 'factory/coldroom-1/BTtoMQTT'

Each sensor arrives on factory/coldroom-1/BTtoMQTT/<sensor id>. The bridge treats coldroom-1 as the machine and puts the sensor id in front of each field (A4C138000001.tempc), so several tags in the same room never overwrite each other. Run end to end with Theengs-style messages on 2026-10-31; the field names depend on the sensor brand, so check them in the next step.

Run Theengs Gateway as a service the same way as the bridge (a systemd unit) so it starts after a reboot.

Set up the MQTT broker (once per plant)

The sensors publish their readings to a broker: a small program that receives MQTT messages and hands them to whoever subscribes. Mosquitto is free and runs on a Raspberry Pi, an old PC or a small industrial box on the plant network. You need one per plant, not one per machine. If you already have a broker (Node-RED, Home Assistant, an IoT gateway), use it and skip this step.

Install Mosquitto
# Raspberry Pi OS, Debian or Ubuntu
sudo apt update
sudo apt install -y mosquitto mosquitto-clients

# One user for the sensors and one read-only user for testing
sudo mosquitto_passwd -c /etc/mosquitto/passwd sensors
sudo mosquitto_passwd /etc/mosquitto/passwd viewer
Require a password
# /etc/mosquitto/conf.d/factory.conf
listener 1883
allow_anonymous false
password_file /etc/mosquitto/passwd
acl_file /etc/mosquitto/acl
Who can publish and who can only read
# /etc/mosquitto/acl
user sensors
topic readwrite factory/#

user viewer
topic read factory/#
Start it and watch messages arrive
# Mosquitto 2 wants these files readable only by its own user
sudo chown mosquitto: /etc/mosquitto/passwd /etc/mosquitto/acl
sudo chmod 0700 /etc/mosquitto/passwd /etc/mosquitto/acl

sudo systemctl restart mosquitto
sudo systemctl enable mosquitto

# Watch everything that arrives (Ctrl+C to stop)
mosquitto_sub -h localhost -u viewer -P 'viewer-password' -t 'factory/#' -v
Give the Raspberry Pi a fixed IP address (a DHCP reservation on the router) so the sensors can always find it. Every example below uses 192.168.1.20. Keep the broker on the plant network; it does not need to be reachable from the internet.

Check the readings with Claude before you connect anything

Before the data goes anywhere, make sure the sensor is telling the truth. Record two minutes of messages to a file and ask Claude (or ChatGPT) to check them. This catches the usual first-day problems (a clamp on the wrong cable, a probe reading the room instead of the pipe, a sensor that only reports when something changes) while you are still standing at the cold room.

Record two minutes of messages (Raspberry Pi, Mac or Linux)
# Record 2 minutes of messages to a file you can give Claude or ChatGPT
mosquitto_sub -h 192.168.1.20 -u viewer -P 'viewer-password' \
  -t 'factory/#' -v -W 120 | while read -r line; do
  echo "$(date -u +%Y-%m-%dT%H:%M:%SZ) $line"
done > sensor-sample.txt
The same on Windows
# Windows PowerShell, with Mosquitto installed from mosquitto.org
& "C:\Program Files\mosquitto\mosquitto_sub.exe" -h 192.168.1.20 -u viewer -P viewer-password `
  -t "factory/#" -v -W 120 | ForEach-Object { "$(Get-Date -Format o) $_" } | Out-File sensor-sample.txt
Prompt
Paste into Claude or ChatGPT with sensor-sample.txt attached
I've attached sensor-sample.txt: two minutes of MQTT messages from a sensor I just fitted to the cold room.
Each line is: time, topic, payload.

Please check it for me:
1. List each topic and every numeric field in it, with the min, max and typical value.
2. Tell me whether the values are physically plausible for the cold room. A chilled room should hold 0–5 °C and a freezer about −18 °C or colder; the temperature should rise when the door opens and recover within minutes. Tell me each sensor id, its temperature range, and how often it reported.
3. Point out gaps longer than 30 seconds, repeated identical values, or fields that are always 0.
4. Say which fields are worth sending to InduQT as signals and which I can ignore.
Answer in a short table, then a list of anything I should fix before I wire it up.

Claude Code or Claude desktop with a terminal can run the mosquitto_sub command for you: ask it to "subscribe to factory/# on 192.168.1.20 as viewer for two minutes and check the readings". Either way the readings stay on your laptop: nothing is stored in InduQT until you wire it up in the next step.

Using a cloud broker (HiveMQ Cloud, EMQX Serverless or your own server with TLS) instead of one on the plant network? Add the free InduQT connector to Claude (https://claude.ai/directory/connectors/induqt) and Claude can listen to the broker for a few seconds itself:

Prompt
Claude with the InduQT connector
Use InduQT to preview my MQTT broker before I connect it:
url mqtts://<your-cluster>.hivemq.cloud:8883, topic factory/#,
username viewer, password <viewer password>. Listen for 10 seconds.
Then tell me which topic level names the machine and which fields are numeric.

Wire it to InduQT

Once the readings look right, send them to InduQT. The simplest way is a small bridge on the same Raspberry Pi: it listens to your broker and forwards every number to InduQT over HTTPS. It works on every InduQT plan, including the free one (up to 3 machines), and nothing on the plant network has to be opened to the internet.

  1. In Claude with the InduQT connector, paste the prompt below. Claude creates the site, the machine and a key that can only send readings to that site. (No Claude? Do the same in the InduQT app: Add machine with the same externalId, then Settings → API keys → a key with the ingest scope, limited to the site.)
  2. Copy the key Claude shows you. It is shown once.
  3. Start the bridge on the Raspberry Pi with that key.
  4. Ask Claude for the latest values, and set the normal bands.
Prompt
1 · Claude creates the machine and the key
Set up InduQT for this sensor:
1. Create a site called "Plant 1" (skip if it already exists).
2. Create a machine named "coldroom-1" with externalId "coldroom-1" and family "chillers".
3. Create an ingest key for the site called "Raspberry Pi bridge" and show it to me once.
After I start the bridge, I'll ask you to check the latest values. The signals will be one tempc, hum and batt per sensor id.
2 · Start the bridge
python3 -m venv ~/induqt && source ~/induqt/bin/activate
pip install "paho-mqtt>=2.0" requests

export MQTT_HOST=localhost MQTT_USER=viewer MQTT_PASSWORD='viewer-password'
export MQTT_TOPICS='factory/#'
export INDUQT_API_KEY='iq_live_…'   # the site key Claude or the app created for you
python3 induqt_bridge.py
induqt_bridge.py (the whole bridge, about 120 lines)
induqt_bridge.py (the whole bridge, about 120 lines)
#!/usr/bin/env python3
"""
induqt_bridge.py — forward MQTT sensor messages to InduQT.

Subscribes to your local broker, turns each message into numbers, and posts them
to the InduQT ingest API in batches. Works on every InduQT plan, including the free one,
and your broker never has to be reachable from the internet.

  factory/<machine>/<anything>        ->  machine = <machine> (matched to the machine's externalId)
  factory/pump-3/vibration {"vib_rms_x_g": 0.12}  ->  signal vib_rms_x_g
  factory/comp-1/status/em:0 {"a_current": 12.4}  ->  signal em_0.a_current
      (two or more levels after the machine: the last level names the group, so
       two probes or two channels never overwrite each other)
  {"temperature": {"tC": 41.2}}       ->  signal temperature.tC
  factory/furnace-1/temp  21.7        ->  signal temp (a bare number takes the last level)

pip install "paho-mqtt>=2.0" requests
"""
import json
import os
import re
import threading
import time

import paho.mqtt.client as mqtt
import requests

MQTT_HOST = os.environ.get("MQTT_HOST", "localhost")
MQTT_PORT = int(os.environ.get("MQTT_PORT", "1883"))
MQTT_USER = os.environ.get("MQTT_USER")
MQTT_PASSWORD = os.environ.get("MQTT_PASSWORD")
TOPICS = [t.strip() for t in os.environ.get("MQTT_TOPICS", "factory/#").split(",") if t.strip()]
MACHINE_LEVEL = int(os.environ.get("MACHINE_LEVEL", "1"))  # factory/<machine>/... is level 1
SEND_EVERY = float(os.environ.get("SEND_EVERY", "10"))     # seconds between posts
IGNORE = set(os.environ.get("IGNORE_FIELDS", "id,ts,time,timestamp,unixtime,Time").split(","))
INGEST_URL = os.environ.get("INDUQT_URL", "https://api.induqt.ai/v1/ingest")
API_KEY = os.environ["INDUQT_API_KEY"]  # a site key from InduQT (Settings -> API keys)

BAD = re.compile(r"[^A-Za-z0-9_.\-]")
buffer, lock = [], threading.Lock()


def key(name):
    return BAD.sub("_", name)[:64]


def numbers(prefix, value, out):
    """Collect every number in a JSON value; true/false become 1/0."""
    if isinstance(value, bool):
        out[key(prefix)] = 1 if value else 0
    elif isinstance(value, (int, float)):
        out[key(prefix)] = value
    elif isinstance(value, str):
        text = value.strip().lower()
        if text in ("on", "true", "online"):
            out[key(prefix)] = 1
        elif text in ("off", "false", "offline"):
            out[key(prefix)] = 0
        else:
            try:
                out[key(prefix)] = float(text)
            except ValueError:
                pass
    elif isinstance(value, dict):
        for k, v in value.items():
            if k not in IGNORE:
                numbers(f"{prefix}.{k}" if prefix else k, v, out)


def on_connect(client, userdata, flags, reason_code, properties):
    print(f"MQTT connected ({reason_code}); subscribing to {TOPICS}")
    for t in TOPICS:
        client.subscribe(t, qos=1)


def on_message(client, userdata, msg):
    levels = msg.topic.split("/")
    if len(levels) <= MACHINE_LEVEL:
        return
    machine = levels[MACHINE_LEVEL]
    try:
        payload = json.loads(msg.payload.decode("utf-8", "replace"))
    except ValueError:
        payload = msg.payload.decode("utf-8", "replace")
    values = {}
    group = levels[-1] if len(levels) - MACHINE_LEVEL > 2 else ""
    if isinstance(payload, dict):
        numbers(group, payload, values)
    else:
        numbers(levels[-1], payload, values)
    if values:
        with lock:
            buffer.append({"machine": machine, "ts": int(time.time() * 1000), "values": values})


def sender():
    while True:
        time.sleep(SEND_EVERY)
        with lock:
            batch = buffer[:500]
        if not batch:
            continue
        try:
            r = requests.post(
                INGEST_URL,
                headers={"Authorization": f"Bearer {API_KEY}"},
                json={"readings": batch, "autoCreate": True},
                timeout=15,
            )
            if r.status_code < 300:
                with lock:
                    del buffer[: len(batch)]
                print(f"sent {len(batch)} readings: {r.json()}")
            elif r.status_code in (400, 401, 403):
                print(f"InduQT refused the batch ({r.status_code}): {r.text}")
                with lock:
                    del buffer[: len(batch)]  # fix the key or mapping; retrying will not help
            else:
                print(f"InduQT returned {r.status_code}; will retry")
        except requests.RequestException as e:
            print(f"network error, will retry: {e}")
        with lock:
            del buffer[:-5000]  # keep at most ~5,000 readings while offline


client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, client_id="induqt-bridge")
if MQTT_USER:
    client.username_pw_set(MQTT_USER, MQTT_PASSWORD)
client.on_connect = on_connect
client.on_message = on_message
threading.Thread(target=sender, daemon=True).start()
client.connect(MQTT_HOST, MQTT_PORT, keepalive=60)
client.loop_forever()
Keep it running after a reboot (systemd)
Keep it running after a reboot (systemd)
# /etc/systemd/system/induqt-bridge.service  — keeps the bridge running after a reboot
[Unit]
Description=MQTT to InduQT bridge
After=network-online.target mosquitto.service

[Service]
User=pi
EnvironmentFile=/home/pi/induqt-bridge.env
ExecStart=/home/pi/induqt/bin/python3 /home/pi/induqt_bridge.py
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

# then:
# sudo systemctl daemon-reload && sudo systemctl enable --now induqt-bridge
# journalctl -u induqt-bridge -f

The bridge treats the topic level after factory/ as the machine (it matches the machine's externalId and creates it if needed), turns every number in the message into a signal (nested fields become names like temperature.tC; when the topic has a group after the machine, such as Shelly's status/em:0, the group goes in front, as em_0.a_current, so two channels never overwrite each other; true/false and on/off become 1/0) and sends a batch every 10 seconds. It was run end to end on 2026-10-31 against Mosquitto 2 with Shelly Gen2, Theengs and plain-number messages. Prefer Node-RED? The same bridge as a Node-RED flow is on the gateway guide.

Prompt
3 · Check it arrived and set what normal looks like
Show me the latest values InduQT has for coldroom-1.
Then set these normal bands so InduQT knows what "normal" looks like: each <sensor id>.tempc between 0 and 5 °C (or your room’s setpoint band).

On the Plant Monitor plan InduQT can also subscribe to a broker directly. Point your sensors (or a Mosquitto bridge) at a cloud broker with TLS, then ask Claude to "create an MQTT connector for this broker, machine from topic level 1", or add it in the app under the site → Connect data → MQTT broker.

What InduQT does with it

  • Learns the room’s normal pattern (defrost cycles, door openings) so a normal defrost is not an alarm.
  • Warns when the room takes longer and longer to recover, an early sign of a refrigeration fault.
  • Flags a sensor that stops reporting or whose battery is low.

Frequently asked questions

Can InduQT read Bluetooth sensors directly?

No. A gateway turns Bluetooth into MQTT (Theengs Gateway, a Shelly BLU Gateway, or an ESP32 running OpenMQTTGateway), and InduQT reads the MQTT data through the bridge or a broker connector.

How far does Bluetooth reach?

Typically 10–30 m indoors, much less through metal walls. Add a second gateway rather than fighting range.

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