A Heltec V3 LoRa Dev Board Acts as a Clever Power Monitor for Boosted Generator Efficiency

Pseudonymous maker "SeansARobot," hereafter simply "Sean," has boosted the efficiency of a backup power generation system — by capturing and decoding radio signals sent out from a household smart meter, with a little help from OpenAI's ChatGPT large language model (LLM).

"I live in Houston and the grid is … janky," Sean explains. "Thunderstorm pops up — bye lights. Hurricane comes through — no power for a week. Whole home backup generators are pricey and I didn't want to spend the money on one. So, I made a whole home backup power solution with a portable inverter generator, interlock kit, and AC soft start. The 'problem' is that I don't know when the grid power returns when the generator is active. I have to go outside and check the meter to see if text has appeared. So, I often burn more fuel than I really need to because I don't know when the grid is active again."

Sean readily admits that there are several possible solutions to this problem, and points to simply using a non-invasive current clamp on the incoming power feed and an Espressif ESP32 or similar wireless microcontroller to fire off a signal when power is restored as being "the right solution." However: "the fun solution," Sean notes, "is detecting RF [radio-frequency] packets from the meter."

Armed with a Heltec LoRa 32 V3 board, built around an Espressif ESP32, Sean was able to capture the packets transmitted by the household smart meter — then asked OpenAI's ChatGPT large language model to figure out what protocol was in use by looking at an image of the meter itself. "My meter uses a 915 MHz FSK [Frequency-Shift Keying] protocol," the maker says. "I don't really care about what the packet says (although that's phase two), just that it is firing off packets."

An Arduino sketch running on the Heltec sends alerts over Wi-Fi when the meter is ticking over, with a simple watchdog timer — the meter sends out its packets every ten minutes when powered, so the Heltec only sends out a power-restored alert when it has been longer than ten minutes since the last packet was seen — keeping it from spamming the messages.

More information is available in Sean's Reddit post; the maker has promised to upload the code once it has been cleaned up. "[I just need to sanitize a few lines," Sean explains, "and remove some swear word comments." The next step: automating the switchover from the generator to mains power.