# Measure Volt, Amps, Watt and Kwh of an external 12V system

I saw online some cheap hardware ~10\$ that can measure Volt, Amps, Watt and Kwh and display the results on an LCD screen.

I could buy and plug these on my 12V solar panel system to monitor it. (5 of them)

But thinking about it, I wish to use my RPI to monitor these numbers. - Trigger some events on specific values.
And display all of it in a web interface or whatever. (That won't be a problem.)

My question is : What kind of hardware can I use to simply measure the Volt, Amps, Watt and Kwh and send the value to my RPI ? (in 5 different places in the circuit.)

• Get yourself a meter which supports UART or I2C. Jun 27, 2019 at 13:18

Get yourself a ADC with a range that suits you(plenty of hats) with enough inputs to measure voltages and currents. You can measure currents multiple ways, with current clamps(that doesn't require another hat) or use a current meter.

These hats mostly work with i2c, and come with python / c examples.

I expect you to know how to use the voltage and current to calculate the watts and from that kWh.

You can add some cool power quality measurement routines on your data as well. The pi is powerful enough.

• I wish ! Do you have a name or link about these hats ? Jun 27, 2019 at 14:49
• There are a lot of hats out there. I wouldn't know a hat by name that measures up to 20 V(or you could voltage divide). I had success with the `ADC PI` in the past. Jun 27, 2019 at 14:58

Answering my own question, so you can tell me if it's a good idea.

I already made a working system with an ADC (Analog to Digital Converter) that can convert the voltage to an LED with a potentiometer with some C code. - `PCF8591`

• Can i simply buy an `ACS712` and send 4 different analog signals to the `PCF8591` ? (It does have 4 analog inputs)

And then I should be able to use I2C to send to my Raspberry Pi.