connecting wattmeter to arduino ?

[hussain.omail]

Hi guys,
I have 4 loads (lamps ,motors and etc) connected to an arduino
my question is how can i measure the power consumed by these loads
can I connect the wattmeter to the arduino ? or if u have any other ideas that will be great
thanx

 

[(*steve*)]

Are the loads powered from AC or DC and what is the voltage?

 

[hussain.omail]

the loads are all ac loads

 

[davenn]

the loads are all ac loads

you didn't answer the second part of Steve's question

what is the voltage ?

 

[hussain.omail]

All of them 220

 

[hussain.omail]

But they're connected to a relay to change the voltage I don't know it exactly

 

[(*steve*)]

Ok 220 VAC switched by a relay.

It is actually quite difficult to measure power (accurately) in this case. The current does not necessarily vary in proportion to the instantaneous voltage.

In addition to this, you have the problem of needing to interface your circuit to 220 VAC. You need to isolate the circuit from this high voltage for safety, but you need to know what you're doing.

Perhaps you can tell us why you need to do this. There may be an easier way of solving the problem.

 

[hussain.omail]

our project is to receive a message or a signal that say u need to lower the power consumption from 10KW to 8KW so I need to know the power from the loads to know which load to shut down >.... thanx

 

[Bluejets]

Add a small relay to each load, determine which loads/combinations add up to 8 kw, send a message(dead contact) to an arduino input if the additional relay is energised.
Hint, basically a logic circuit, this, or this and this etc.
Only 4 units, can't be too dificult.