Advice needed

Hi all,

I'm a newbie in energy monitoring and I'm trying to build a power monitor interfacing the max 78M6610+PSU to an arduino.

As voltage sensor I'll use a resistor bridge but I'm not sure about the current sensor. The current to be measured is single phase 220VAC and 5A max. My question is if a hall sensor acs7714 type will do the trick. CT's are really expensive as you know...

Please MOD move this thread to a proper location if not in the right one


Robert Wall's picture

Re: Advice needed

My first observation is the IC does not provide isolation, therefore if you intend to use a galvanic connection to the mains supply as you say you do, then THE WHOLE CIRCUIT MUST BE CONSIDERED LIVE. That means it must be either totally enclosed inside an earthed metal enclosure, or double insulated. You cannot work on it without observing the correct safety precautions. If you need to reprogram anything, it must be disconnected before you open up the box, and you cannot connect (say) a laptop to debug the software unless you have isolation in the data leads, or you risk damaging yourself or your computer, or both.

If you are that worried about saving money (and you might not be saving when you factor in the cost of a separate power supply for the data isolation circuitry) why not simply use a resistive shunt? It can drop 175 mV maximum, and the dissipation will be less than 1 W, so not excessive.

Personal safety is a very good reason why we recommend the use of transformers for measuring both voltage and current. You can get an insight into the precautions necessary when making a direct connection to the mains electricity supply in this:

scaf's picture

Re: Advice needed

Thanks for you answer.

I've just read one other solution and I will try to make some tests about it - embedded pcb CT(don't really know if it can be called like that).

Maybe a silly idea. I'll post results later

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