So I have a solar panel with an mppt module attached to it. For the panel I have then at best I can get 0.8 amps at 18 volts or 14 watts. For a while I have been wondering what the panel outputs on a rainy day like today. If the panel produces enough power than I would love to try to produce some heat with it as a passive heating system. Will not be much but a small nudge to maybe offset the toddler leaving the door open once or twice.

Ideally I would like to monitor voltage and current with a low voltage cut-off. Figured it would probably come in two flavors: current sensor, and voltage sensor.

  • Sparkfun’s ACS723 looks promising but is $10. This board can sense current up to 5 amps.
  • According to ElectornicsHub most of these are just voltage dividers bringing the voltage into the range of the sensing network. If this is correct I would be taking at most 14 watts at 5 volts or 3 amps into the resistor network. Luckily someone on StockOverflow already answered the question. Although this begs the question what is the maximum draw on an Arduino analog read. Attempting to find the maximum amperage of an arduino input pin lead me down a rabbit hole regarding pull-up and pull-down resistors which answers the question of how voltage is sensed. Well an Uno should not exceed 20mA at 5 volts.
  • Looks like DroneBot Workshop had a similar desire to measure voltage and amperage using an Arduino. They go through a series of methods on how to measure but eventually settle on the INA219 from Adafruit. An INA219 uses I2C to interact with an MCU. Downside is it requires soldering. Electrical characteristics are great though: 26v at 3.2A with a resolution of 0.8mA. Not sure on the voltage resolution though.