Advanced Arduino Frequency Scanner

Author: Bocaletto Luca

This project upgrades the basic pulse‐counting scanner into a high‐resolution, wide‐range instrument using Arduino’s Timer1 Input Capture. You’ll get instant period readings, automatic smoothing, dynamic range up to several MHz, and a clean I²C LCD interface.

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1. Key Features

• Direct Period Measurement via Timer1 Input Capture on ICP1 (digital pin 8)
• Wide Dynamic Range (from a few Hz up to 2 MHz+ with prescaler options)
• Exponential Moving Average for stable readout
• I²C 16×2 LCD Display for real‐time feedback
• Optional Serial Logging for PC/SD‐card integration

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2. Components

• Arduino UNO (16 MHz)
• Schmitt‐trigger comparator (e.g. LM311/LM393) + BNC connector
• 16×2 I²C LCD (PCF8574 module)
• Pull-up resistor for comparator output (10 kΩ)
• Breadboard, jumpers, 5 V supply (USB or external)
• (Optional) SD-card module + Real‐Time Clock for timestamped logs

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3. Hardware Wiring

Signal In ──► [Comparator] ──► TTL Output ──► Arduino Pin 8 (ICP1)
                 │                     
                VCC (5 V)
                 │                     
                GND

Arduino A4 (SDA) ──► LCD SDA
Arduino A5 (SCL) ──► LCD SCL
Arduino 5 V ──► LCD VCC
Arduino GND ──► LCD GND

Tip: Add a small RC filter (10 kΩ + 100 pF) ahead of the comparator to clean jittery inputs.

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4. How It Works

1. Comparator shapes any analog or RF source into clean TTL pulses.
2. Timer1 runs at F_CPU/8 (2 MHz → 0.5 µs tick) and captures the timer value on each rising edge (ICP1 ISR).
3. Period Calculation: ISR computes Δticks between consecutive edges → period (µs) → frequency (Hz).
4. Smoothing: an exponential moving average (α = 0.1) filters out noise while preserving responsiveness.
5. Display: Shows both raw and smoothed frequency on the LCD.

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5. Calibration & Verification

• Low‐frequency test: verify down to <10 Hz by observing stable updates.
• High‐frequency test: feed a 1 MHz signal; confirm correct readout up to ~2 MHz.
• Smoothing α: adjust 0 < α < 1 to trade off noise vs. response time.
• Optional: add an auto‐prescaler selector to switch Timer1 prescalers for extreme ranges.

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6. Next‐Step Extensions

• Serial/SD Logging: timestamped CSV output for trend analysis.
• Automatic Range Switching: detect Δticks out of bounds and change prescaler on the fly.
• Graphical Touch Display: show history or simple FFT spectrum.
• Bluetooth/Wi-Fi Module: remote monitoring via smartphone or web dashboard.
• Peak-Hold & Min/Max: capture transient spikes or dips over a user‐set interval.