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Radio Frequency power detector "sniffer"

Added to IoTplaybook or last updated on: 12/03/2022
Radio Frequency power detector "sniffer"


The RF detector can be used as linear instrument monitor or as threshold/comparator alarm, it depends from DipSwitch1-1 setting: On=instrument, Off=comparator. The threshold level comes from 10K trimmer you may set as you like. In instrument mode both buzzer and top panel RGB LED change their level (sound & light) depending of the detected RF power level. DipSwitch1-2 setting: On=buzzer on, Off=buzzer off.

By the way of DipSwitch2-1 and DipSwitch2-2 you may change the colour of the top panel RGB LED: 00=off 01=red 10=green 11=blue.

Additionally it is an USB mini connector to recharge the battery from an USB power source, and a red colour LED to show when it is charging.

Things used in this project

Hardware components

Arduino Nano R3
Arduino Nano R3
× 1



Microchip ATtiny 1614 Processor
× 1

Inspired from John Bradnam's ATtiny 1614 Project I bought a couple of this microcontrollers to take a new way and enjoy a new adventure, I made MyTiny first testing circuit. Everything is working on my choice to power it at 3.3v. Up to today I tested and verified: digitalRead, digitalWrite, analogRead, analogWrite both PWM and DAC; I provided a serial monitor though pins RX/TX <-> FTDI serial interface and SoftwareSerial library; finally I connected an OLED 128x32 display by the way of SDA/SCL and Wire library. Cool!

ATtiny programming:

To program the ATtiny by the way of an Arduino NANO and IDE please read Bradnam's instructions at above link. Here some of it:

  • install jtag2updi sketch into Nano
  • connect a 10uF 25V electrolitic capacitor on Nano between RESET(+) and GND(-)
  • connect a 4.7K resistor and a wire from Nano pin 6 to ATTINY UPDI pin
  • connect GND from Nano to ATTINY
  • connect +5V from Nano to ATTINY
  • keep connected Nano and Arduino IDE
  • change programmer to "jtag2updi"
  • change board to "ATtiny1614..."
  • change other parameters as per attiny-setup.jpg screenshot (see below)
  • compile the sketch for ATTINY
  • Upload sketch to ATTINY (try...)

Screenshot of the parameters I used on my Arduino IDE
Screenshot of the parameters I used on my Arduino IDE

RF power detector overview
RF power detector overview

Components list:

  • LT5534 50-3000Mhz RF power detector IC
  • ATtiny 1614 3.3V MCU
  • LIR2450 3.6V rechargeable battery + PCB holder
  • MCP73831 Li.Po. controller charger IC
  • Active buzzer
  • 2x two dipswitch
  • 10k trimmer
  • RGB 4 pins led
  • Red led
  • SMA-M (144-430Mhz small antenna)
  • SMA-F panel connector, square + screws
  • On/off switch
  • 2x SMD 4.7uF capacitors
  • 2x SMD 1nF capacitors
  • 2x SMD 1.0uF capacitors
  • SMD 10k resistor
  • SMD 22k resistor
  • SMD 47 resistor
  • SMD 100pF capacitor
  • SMD 470 resistor
  • SMD SOT-23 662K 3.3V voltage regulator IC
  • 3 pins connector for UPDI (1=UPDI, 2=3.3V, 3=GND)
  • SMD USB-mini connector
  • Plastic or metal box 51x51mm internal size
  • 9x copper pass through rivets

Typical schematic diagrams:

Datasheet test circuit of RF detector 5534 IC
Datasheet test circuit of RF detector 5534 IC

Datasheet test circuit of Li.Po. charging 73831 IC
Datasheet test circuit of Li.Po. charging 73831 IC


  • Capacitors and resistors SMD size is C1206;
  • Components are small, and 5534 RF detector IC is VERY SMALL! To solder it I had to use an electronic magnifier!
  • The 22kohm is the charging current resistor. The formula is: 1000/22000=0.045A (45mA). In the typical application schematic diagram shown above the resistor is a 2kohm, it means the charging current will be 1000/2000=0.5A, too much for this small coin battery. I had to modify it of course;
  • Remember to connect a specific antenna for every RF frequency range you want to detect; in some cases a simple ring wire of any lenght can be enough as "antenna", specially when the RF signal is strong;
  • LT5534 datasheet says to not overload the RF input pin with signals > 10dbm (i.e. handheld 5W radio tx near the IC); if it is the case, I suggest to put an attenuator between the antenna and the box (i.e. 20dbm SMA-MF serial external attenuator - see the picture below); additionally, use full metal box, or cover the interiors of the plastic box with copper foil, or paint/spray and 80°C cook if necessary (read material datasheet) with conductive material the interiors of the box (i.e. graphite), to avoid RF signals passing through the box; the RF signals should pass through antenna only... Burning the IC is a real possibility: I did it one time.

RF 6 Ghz RF 20db SMA attenuator
RF 6 Ghz RF 20db SMA attenuator

Very handy construction, I like it
Very handy construction, I like it

An electronic magnifier is useful for SMD soldering
An electronic magnifier is useful for SMD soldering

Enjoy it!

Schematics - PCB rf-sniffer top

PCB rf-sniffer bottom

PCB rf-sniffer topsilk

Code - RF-sniffer code





"From an early age I learned to not use pointers"

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This article was originally published at It was added to IoTplaybook or last modified on 12/03/2022.