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ChillPoint — Handheld Thermochron Temperature Mgr

chillPoint — handheld Wi-Fi reader for iButton temperature loggers

geoffrey-wellsGeoffrey Wells
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Formally called senseReader, ChillPoint is a handheld device that allow full management of Thermochron Temperature Sensor iButtons from Maxim(now Analog Devices). The unit has an embedded web UI that is used to view temperature data, and set new data logging missions.

What's This Thing

iButton data loggers, DS1921 Thermochron and derivatives are those little stainless-steel coin-shaped chips that ride along in cold-chain shipments, lab freezers, vaccine coolers, and field experiments, quietly recording temperature (and humidity) for weeks at a time. They're rugged and cheap — but actually using them traditionally means a USB blue-dot adapter tethered to a Windows PC running the vendor's aging 1-Wire software.

ChillPoint throws all of that away. It's a handheld, battery-powered ESP32-C6 device with a 1-Wire probe on the front. Touch an iButton to the probe and the device reads it, parses every register, and stores the result on its own flash. There's no app to install: the device hosts its own Wi-Fi access point an web UI, so any phone, tablet, or laptop becomes the screen.

From the web UI you can:

  • Read an iButton — ROM ID, mission status, min/max, the full datalog buffer, histogram bins, and alarm events, charted in the browser.
  • Configure a new mission — sample rate, alarm thresholds, rollover, resolution.
  • Download the logged data as JSON, or
  • Batch-upload it to a remote "Data Host" HTTPS endpoint for archiving.

Why I built it

The vendor toolchain is the bottleneck. If you have a freezer full of loggers to read out in the field, dragging a laptop and a USB adapter around is miserable, and the desktop software is single-platform and dated. I wanted something I could hold in one hand, tap a chip against, and read on my phone — the way modern hardware should work. The ESP32-C6 has Wi-Fi 6, a generous 8 MB of flash, and enough RAM to host a real web app, which makes the "the device is the server" approach practical.  The hardware schematics and software will be open source.

How it works

Hardware

  • MCU: ESP32-C6 (8 MB flash, Wi-Fi 6 / BLE)
  • Probe: 1-Wire iButton reader
  • Power & timekeeping: RV-3028-C7 RTC and a MAX17048 fuel-gauge battery monitor share the I²C bus
  • HMI: a mode button plus a small bank of status LEDs (mode, config, pass/fail) and a PWM buzzer for audible read feedback
  • Storage: on-board LittleFS — each reading and each mission profile is a JSON file on flash

Current Status

The hardware development is almost finished.  A few more spins for layout issues, and the membrane switch graphics need updating.  There is a pre-launch page on CrowdSupply in case you are interested in the project: https://www.crowdsupply.com/g9six/chillpoint

  • What's a Thermochron?

    Geoffrey Wells • 07/02/2026 at 13:44 • 0 comments

    What Is a Thermochron iButton?

    One of the questions I get most often is, "What exactly is a Thermochron iButton?"

    If you've never seen one before, you're not alone. Despite being used around the world for temperature monitoring, they're still relatively unknown outside of industries that rely on them.

    A Thermochron iButton is essentially a self-contained temperature data logger packaged inside a rugged stainless-steel can about the size of a coin (roughly 17 mm in diameter). Inside that tiny enclosure is:

    • A precision digital temperature sensor
    • A real-time clock
    • Non-volatile memory for storing measurements
    • A long-life internal battery
    • A unique factory-programmed serial number
    • A 1-Wire communication interface

    Once programmed, the iButton wakes itself up at user-defined intervals—anywhere from once a minute to every few hours—records the temperature, stores the reading internally, and then goes back to sleep to conserve battery power. Depending on the model, it can store thousands of temperature samples and operate unattended for months or even years.

    Why are they so popular?

    The biggest advantages are their simplicity and durability.

    Unlike many modern data loggers, a Thermochron doesn't need Bluetooth, Wi-Fi, cellular service, or even a display. You simply configure it, place it where you want to monitor temperature, let it collect data, and retrieve the results later.

    Because they're sealed in stainless steel, they're resistant to dirt, moisture, vibration, and rough handling, making them ideal for demanding environments.

    Common applications

    You'll find Thermochrons being used for:

    • Cold-chain shipping
    • Vaccine and pharmaceutical storage
    • Food transportation
    • HVAC performance testing
    • Scientific research
    • Environmental monitoring
    • Museums and archives
    • Agriculture
    • Industrial process monitoring

    Anywhere someone needs to know what the temperature was over time, a Thermochron is a good candidate.

    Why I built ChillPoint

    Although the iButtons themselves are incredibly capable, the tools for configuring and reading them have traditionally required a Windows PC and a specialized USB adapter. That's fine in a lab, but it's not very convenient when you're in the field.

    The goal of ChillPoint is to make working with Thermochrons much easier by providing a completely handheld, battery-powered device that can configure iButtons, download their logged data, and review temperature records without needing a laptop.

    Please consider subscribing to my campaign: https://www.crowdsupply.com/g9six/chillpoint

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