Syncing 2 Phases - Energy Monitor DIY Arduino

[Powerpoucher]

Hi all,

Doing some energy monitoring of some various equipment using ct clamps and an diy arduino based energy monitor. I have limited number of arduino inputs available so have been experimenting to boost the capacity of the monitor without using multi arduino. I have found no problem joining 2 or 3 clamps into one input if they are of the same phase but what would i need to do to sync the tiny voltage between clamps so that i could put all of my lights, which are split between the 3 phases into one input using 3 clamps.

I know the answer if there is one would be to use capacitors but it would be great if any1 could tell the values or configuration and what i would use to measure to make sure I've done it right it'd be much appreciated.

Thanks

Samuel

 

[NascentOxygen]

Hi Powerpoucher. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

The clamps are sensing the amplitude of the current?

You have 3 clamps, and would like to produce a signal equal in amplitude to the sum of the three individual signal amplitudes? Do you want this sum to be a single-phase AC signal, or a DC level? What is your line frequency?

In any case, I think it would have to be an op-amp circuit.

 

[Powerpoucher]

Hi Powerpoucher. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

The clamps are sensing the amplitude of the current?

You have 3 clamps, and would like to produce a signal equal in amplitude to the sum of the three individual signal amplitudes? Do you want this sum to be a single-phase AC signal, or a DC level? What is your line frequency?

In any case, I think it would have to be an op-amp circuit.

You are exacty correct and thank you for putting it in a more coherent form than I did. The line frequency is 50htz and it will need to be a single phase AC signal.

And thanks for the welcome :)

 

[berkeman]

I agree with NO -- use an opamp circuit that does peak detect on each phase, and add those 3 voltages before digitizing with your Arduino.

 

[jim hardy]

You didn't say what does the current wave look like. Phase shifting by capacitors will affect harmonic content of non-sine wave load currents

If this is more than just a hobby application , it might be worth using RMS to DC converters for the phase currents.
Electric company probably hands you a pretty decent sinewave voltage.

http://www.analog.com/static/imported-files/data_sheets/AD737.pdf

around eight bucks at Digikey

application notes here
http://www.analog.com/en/special-linear-functions/rms-to-dc-converters/ad737/products/product.html

Linear Technology has similar products

 

[NascentOxygen]

Doing some energy monitoring of some various equipment using ct clamps and an diy arduino based energy monitor.

Using the fairly simple arrangement I had in mind, it will not produce accurate results when the load predominantly comprises lights with dimmers and speed-controlled ceiling fans. These cause distortions in the current waveform, rendering it non-sinusoidal.

Are you likely to have such loads? (Jim, that true RMS processor sounds handy.)

I'm also interested to know why you prefer the sensor to give you a sinusoidal signal, in preference to a DC level.

 

[Windadct]

If your are looking at different phases and the output of the sensors is AC ( representative V or I ) this really will not work. As an example - if the phases are 180 out of phase - and they both have 100A - the sum will be 0 Amps...
If the output of the sensors is DC Voltage representing the current, then the DC voltages can be summed - possibly in series, depending on the output circuit in the sensor ( YOu may be able to rectify the signal yourself - creat DC ands then sum)- -- Summing with an op amp will work, but you still need to get the V input to the ADC input on the Arduino to 3.3 or 5 V MAX ( basic v divider will work)

However looking at all of this- you are introducing a lot of error...- so each step is not ideal and you are getting further and further from the truth. If you really want to measure energy / power - perhaps a power measuring IC - or try to convert each signal into power first... still I a sure more work than you are asking about.