Arduino Forum

Topics => Science and Measurement => Topic started by: martinocko9 on Jun 12, 2018, 04:02 pm

Title: arduino power monitor
Post by: martinocko9 on Jun 12, 2018, 04:02 pm
i want to measure 6 ac currents and 3 voltage phases.
i dont want to use modules that you screw wires on.
the problem is that i dont know how to measure current with current transformer.
maybe measure voltage drop on resistor but then problem is that voltage is ac.
Title: Re: arduino power monitor
Post by: wvmarle on Jun 12, 2018, 04:14 pm
i want to measure 6 ac currents and 3 voltage phases.
What you mean with this?

What voltage/current are you looking at?

Quote
the problem is that i dont know how to measure current with current transformer.
Well, if nothing else works, read the manual... I'm sure those things come with one.
Title: Re: arduino power monitor
Post by: Paul_KD7HB on Jun 12, 2018, 09:37 pm
i want to measure 6 ac currents and 3 voltage phases.
i dont want to use modules that you screw wires on.
the problem is that i dont know how to measure current with current transformer.
maybe measure voltage drop on resistor but then problem is that voltage is ac.
Before you do anything, determine the current ranges you are monitoring and the voltages you are monitoring. Once those values are determined, then you can research methods of monitoring.

Paul
Title: Re: arduino power monitor
Post by: hammy on Jul 08, 2018, 01:52 pm
This is harder than it looks - to get power you need to multiply current by voltage - but the phase of the two signals is important , so converting ac to its dc equivalent is a problem - unless your load is purely resistive.

There is also a safety issue - to me 3ph implies high voltage , so you need to use designed for the purpose voltage and current transducers. The best route is probably to buy a 3 ph electricity meter with a pulse output and use the pulse output to your Arduino. This will be cheap and safe .

The " don't want to use modules that you screw wires to" seems odd

I'm sure this query turned up
About a year ago ?
Title: Re: arduino power monitor
Post by: MarkT on Jul 09, 2018, 12:02 pm
You can get clamp-on current transformers, but to measure voltage accurately you need a voltage
step-down transformer which has to be connected at the primary side.

If you sample the readings frequently enough you can calculate power directly by averaging over time,
but with many sensors it may prove hard to read frequently enough without an external high speed ADC
Title: Re: arduino power monitor
Post by: hammy on Jul 13, 2018, 11:26 pm
You not only  have to sample , but sample often enough to be able to calculate the phase angle  or  recreate and multiply together the voltage and current signals - this is a big task , with all the bits required, I think it cheaper/safer/quicker to buy proper meters  or interface with an existing metering system.

The original post does not suggest a lot of experience with higher voltages ( sorry if this is not the case) ; so safety first
Title: Re: arduino power monitor
Post by: MarkT on Jul 17, 2018, 02:09 pm
Well sampling at 1kSPS for several channels isn't that hard for a standard Arduino, given the 10kSPS
out-of-the-box max analog sampling speed (which can be increased if wanted at expense of a little accuracy).
Title: Re: arduino power monitor
Post by: wvmarle on Jul 17, 2018, 02:38 pm
Just 1,000 samples or 0.1 seconds of sampling fill up all the RAM of a regular Arduino, leaving no space left to do any calculations on the data or for anything else.
Title: Re: arduino power monitor
Post by: Paul_KD7HB on Jul 17, 2018, 03:46 pm
Well sampling at 1kSPS for several channels isn't that hard for a standard Arduino, given the 10kSPS
out-of-the-box max analog sampling speed (which can be increased if wanted at expense of a little accuracy).
The theoretical voltage sine wave may be distorted by multiple odd harmonics on the power lines because of other equipment being powered on that line.

Paul
Title: Re: arduino power monitor
Post by: anwofis on Jul 18, 2018, 04:08 pm
Just look at this: openenergymonitor.org (https://openenergymonitor.org/forum-archive/node/58.html) For standard AC this should work. e.g. i use it for mains voltage monitoring (it seems accurate within 1-3 V)
Title: Re: arduino power monitor
Post by: hammy on Jul 19, 2018, 11:10 pm
https://www.electricmetersales.co.uk/p/three-phase-meters



Me again ... these guys do 3ph meters , used from £18.50