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Remote power management of a remote amateur repeater site

The Raspberry Pi 2W is a very inexpensive computer on a board. It has a dual core RP2350 microprocessor with 2.4GHz and Bluetooth 5.2, a 150MHz clock speed, 520kB of SRAM and 4MB of on board flash memory. It has a full speed USB 1.1 host/device controller and 26 GPIO pins.

With ideas from the “Geoffg.net” Watering system controller project featured in August 2023 Silicon Chip Magazine I have created a wifi server that allows remote monitoring of the voltage and current of both the loads and the solar charger at The Bluff site of VK5RMG. This repeater system is the centre of the South East Radio Group’s repeater network covering the Lower South East of South Australia and into SW Victoria.

Using an INA226 board readily available from many Internet shops to measure the readings from a shunt resistor we are able to monitor the load (a 2m voice repeater, a 70cm C4FM repeater, three UHF links to other sites, Echolink, and a packet radio system supporting APRS and a Marine tracking system) plus solar.

The critical part is the software and it depends on “MMBASIC for the Picomite” that provides for the establishment of a WIFI connection, a TCP server, TELNET service and USB.

Under normal operation the Rpi PICO is provided with power and of course the correct software. However in this project I use I2C to access the INA226 board that enables the shunt voltage to be read for current and the power leads to be read for up to 36V. It’s a natty little board and comes with its own shunt resistor for twenty amps. However our peak current is above 20A (about 25A) so I have made use of a commercial 0.001 ohm shunt resistor.

The example to the right shows a typical readout with false numbers as it was taken without the INA226 board connected.

Normally it refreshes every 2 minutes and the old data is for 6AM, 9AM, Noon, 3PM, 6PM and 9PM.