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
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!
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...)
- 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:
- 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.
Schematics - PCB rf-sniffer top
Code - RF-sniffer code
"From an early age I learned to not use pointers"
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