Measuring power out from solar panel

[kbman99]

Is there any way that I could measure the power output of a solar panel using the ADC? The panel itself gets up to 10.5V so a voltage divider will be necessary, but how could I also go about measure the current which the solar panel is pushing in order to get the total power? Is there a way to measure current via the IO pins on the PyTrack?

In other words, how can I create a watt meter using the LoPy and Pytrack?

[robert-hh]

@kbman99 For current measuring you can use a hall effect module like the acs712. Take the one with a lowest amp range. It converts a potential free current into a DC signal, which you can measure with the ADC input.

Edit: many of the cheap modules sold on eBay etc. contain wrong labeled chips, like a ACS713-20 instead of a ACS 712-30. They work, but have deviating properties (e.g. 20A DC instead of 30A AC). And also, most of the modules are not built for proper isolation. The chip is built to that, but not the board. So NEVER USE THEM WITH AC mains or at other dangerous voltages at the current sensing side.

[kbman99]

@robert-hh Okay, definitely something to think about. I was wondering if using a super small resistor as a shunt to measure would work, then I remembered that the solar panel voltage of 10.5v wouldn't play too well with the LoPy. I suppose I could also use another larger resistor to come off the node which measures the shunt resistors voltage drop and then just calculate, based on the voltage of the larger resistors value, the actual voltage level measured.

I've also found this breakout board on sparkfun https://www.sparkfun.com/products/12040
Gonna look at the datasheet for the chip itself and see if it would work.

[timh]

@kbman99 probably even easier without having to worry about resistors and such is use an i2c device for measuring current and voltage like https://www.adafruit.com/product/904

I am using i2c to read 4-20ma and devices on Gpy using this https://www.ereshop.com/shop/index.php?main_page=product_info&cPath=143&products_id=805&zenid=03a1ed61b8191b814a00e8fe3c0a93c6

[robert-hh]

@kbman99 This INA169 device is also interesting, because you can set the sensitivity yourself with the appropriate shunt resistor. But the INA219 device @timh mentions is even more interesting, since it takes both voltage and current, and avoids the noisy ADC of the ESP32.