So...I don't even know if this can be done, but what i have learned is that there is almost always a way.. What I want to do is create a amp and volt meter, for my boat. The way that the boat is set up is it has 2 -30 Amp lines at 120 volts. And right now they have analog and I want to create my own. I just don't know where to begin with this new project.
The Arduino can be damaged by greater than 5V or by negative voltage.
You can use a [u]voltage divider[/u] to knock down the voltage, and a diode or full-wave rectifier to take care of the negative voltage. It' also a good idea to add some [u]protection diodes[/u] with any voltmeter.
For measuring current, you pass the current through a small value resistor to generate a small voltage, then using [u]Ohm's Law[/u] to calculate the current.
It's probably going to be tricky to build a circuit that measures voltage and current at the same time because the current resistor is normally floating above ground, so you can't use a true ground.
You should also isolate the power supply from the voltage you're measuring. If you are powering the thing from 12V, that would be a DC-DC converter.
@DVDdoug:- I'm facing the same issue to measure AC power of a load:-
- I'm not able to find any small size Current Transformer/Transducer for this purpose could I use the same logic you gave for measuring AC power??
2)But also if use your logic for measuring current through the resistor than do I need to have a voltage divider circuit? and doing the calculation as AC power involves power factor which is not fixed?
Is there any other way to measure Power consumed in load as my load remotely?
An ac panel meter is much easier to use to get V & I.
You could tap into the panel meter to get V & I info to Auduino. This may not be easy for an amateur.
all you need is a nice 1/2 inch brass rod or plate or threaded rod or some such.
connect it in series with your power supply to create a shunt.
measure voltage accross the shunt.
or, you can be lazy and just buy one.
http://www.mpja.com/Mini-Panel-Meter-Dual-LED-Display-30-Volts-100-Amps-DC/productinfo/32063+ME
@dave-in-nj
I like the threaded shunt idea 
See I am trying to measure 120 volts AC, and i could just buy one, but whats the fun in that? LOL
boatingman39:
See I am trying to measure 120 volts AC, and i could just buy one, but whats the fun in that? LOL
http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
http://www.seeedstudio.com/depot/Noninvasive-AC-Current-Sensor-100A-max-p-547.html
when you said Boat... just thought you were on a generator with DC.
AC is much easier.
Gerry48:
An ac panel meter is much easier to use to get V & I.You could tap into the panel meter to get V & I info to Auduino. This may not be easy for an amateur.
Actually want to use this option for IOT hence it won't be possible to use panel meter just want to know the consumption of 'LOAD' of an AC Power.
Is there any other way to measure AC Power, AC Current & AC Voltage for a load basically for Internet Of Things.
I would be great full if any one provide me solution for this issue.
Ok, so I got the Volt side of this program down, which is great. But now what can i use to measure how much amps i am drawing. See on my boat i have a choice either to run 30 Amps or 60 Amps. I would like to have a precise measurement on how much amperage I'm drawing, so I don''t trip a breaker.
boatingman39:
Ok, so I got the Volt side of this program down, which is great. But now what can i use to measure how much amps i am drawing. See on my boat i have a choice either to run 30 Amps or 60 Amps. I would like to have a precise measurement on how much amperage I'm drawing, so I don''t trip a breaker.
software:
http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
hardware:
http://www.seeedstudio.com/depot/Noninvasive-AC-Current-Sensor-100A-max-p-547.html
Voltage as stated above, a voltage divider should work well.
For measuring current, ever looked at hall effect sensor? ive used these and they seem to work well. If you motor has PWM to control speed, you will nee a low pass filter on the output of the sensor.
this is a 100 amp version but other sizes exist.
KILL A Watt meters are great. It also give the power factor, watts, and VA.
ankurpatel4888:
Actually want to use this option for IOT hence it won't be possible to use panel meter just want to know the consumption of 'LOAD' of an AC Power.Is there any other way to measure AC Power, AC Current & AC Voltage for a load basically for Internet Of Things.
I would be great full if any one provide me solution for this issue.
Voltage Divider will be able to see how much amperage is being used?