# openQCM Wi2 · Electronics

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_openQCM Wi2 · sheet 04 · Electronics_

openQCM Wi2 exploits the potential and simplicity of the Teensy microcontroller — an Arduino-compatible board with a 32-bit ARM processor. A high-precision quartz crystal oscillator automatically tracks frequency changes.

## The signal path

Quartz crystal (in the sensor module, on two pogo pins) → Pierce oscillator (SN74LVC1GX04: keeps the crystal at resonance) → Square wave (one edge per oscillation) → Teensy counter (FreqCount: edges counted over a 1 s gate) → USB (frequency and temperature to the software)

## One count per second.

Every detail is designed to simplify the researcher’s experimental activity. Frequency is measured using the FreqCount library, which counts the number of pulses during a fixed time using the microprocessor’s hardware timer — a procedure that works very well at high frequencies, where many cycles are counted within the gate interval (typically 1 second).

![openQCM Wi2 compact USB-powered QCM](https://openqcm.com/wp-content/uploads/2018/04/Quartz_Crystal_Microbalance-openQCM_Wi2-Wireless-2-1024x612.jpg)

## Wireless-ready.

A compact, USB-powered driver designed for wireless-ready acquisition — high-precision oscillator tracking in a footprint small enough for any benchtop or field setup. Expansion headers on the board take a Wi-Fi module or a PCB of your own.

## The boards

- **Main board:** 2 layers, 59.9 × 36.8 mm, FR-4 TG150, 1.6 mm, 1 oz copper, ENIG
- **Oscillator:** SN74LVC1GX04, Pierce topology
- **Regulator:** LP2985, clean 3.3 V supply
- **Expansion:** Headers for a Wi-Fi module or custom PCB
- **Proximity board:** 31 × 29 mm, MCP9808 (±0.25 °C), two pogo pins, status LED, USB 3.0 connector to the main unit
- **Schematics:** Open source

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