Circuit Upgrade

A project log for LoRa Dark Star

Low Quiescent Current + Solar Powered 1W LoRa

Capt. Flatus O'FlahertyCapt. Flatus O'Flaherty 12/08/2022 at 18:520 Comments

I want to add a low current draw timer with nano amp rating as I've noticed that the device just keeps on wanting to turn on and do something 10 or 12 times in succession before it finally drains the battery too much. An adjustable timer would be very useful as long as it does not consume more than a few Nano Amps when quiescent. There's an 'AND' type logic gate which only allows the ESP32 to be ressurrected from the dead if both the timer and the energy harvester chip allow it. NPN transistors apparently have much better quiescent current levels than mosfet, in the order of x60 better, so one of these was selected for the main switch. I tried activating this NPN directly from a pin from the ESP32, but it drained current some how and wrecked the battery. Tried putting it through a diode and eventually found that another NPN transistor activating a small relay worked just fine and the battery remained fully charged all day and night. I'd really like to get rid of the relay as it draws about 30 mA, so maybe a bit more experimentation is necessary. But it works fine for now.