# Syncing 2 phases

1. May 21, 2014

### 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

2. May 21, 2014

### Staff: Mentor

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

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.

Last edited by a moderator: May 6, 2017
3. May 21, 2014

### Powerpoucher

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 :)

Last edited by a moderator: May 6, 2017
4. May 21, 2014

### Staff: Mentor

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.

5. May 22, 2014

### 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.

around eight bucks at Digikey

application notes here

Linear Technology has similar products

6. May 23, 2014

### Staff: Mentor

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.

Last edited: May 23, 2014
7. May 23, 2014