This project help you to build a Power and Swr Meter (for HF) using Arduino Uno R3 (or compatible) and cheap board SWR Bridge v.1.4 available on Amazon or Ali Express for about 5$. Despite the very low cost of this project, the POWER and SWR read on the device are very accurate, thanks to the volt watt conversion table written in the source code.
- Arduino Uno R3 (or Nano, all compatible device)
- Display LCD I2C 16 columns 2 rows
- SWR Bridge v1.4 (cheap board)
- 2 PL connectors
- 2 100K resistors (Between FWD -> GND and REV -> GND)
- Metal box
- VCC and GND of the I2C Display to Arduino standard Pins
- SDA of the I2C Display to Arduino A4 analog pin
- SCL of the I2C Display to Arduino A5 analog pin
- FWD of SWR Bridge to Arduino A6 analog pin (with a 100K resistor to GND)
- REV of SWR Bridge to Arduino A7 analog pin (with a 100K resistor to GND)
- Both PL connectors on IN and OUT of SWR Bridge v1.4
NOTE: The IN and OUT of the SWR Bridge v.1.4 are inverted!! This is a bug of the cheap board!!!
- 1 watt = 0.90 volt
- 2 watt = 1.16 volt
- 5 watt = 1.90 volt
- 6 watt = 2.00 volt
- 7 watt = 2.15 volt
- 10 watt = 2.40 volt
- 15 watt = 2.80 volt
- 20 watt = 3.35 volt
- 25 watt = 3.80 volt
- 30 watt = 4.23 volt
- 40 watt = 4.65 volt
This values are valid using a 100K resistor between FWD (and REV) and GND!
You can write your own table by measuring the volt values between FWD and GND with a voltmeter and read the corrisponfance power in watt on the external Power Meter.
The table is stored in rwatt[] array and rvolt[] array of the arduino code.
You can use a resistive divider for increment the scale
NOTE: Pay attention to the voltage on the 5 Volt pin of Arduino. In the source code file, there is a variable (VoltRef)... set it to real value: to me the value is 4.48 volt!! This value is important for the accurate translation of volt value in watt!