# Measuring ac using arduino

Hi ,
I want to measure 20A ac using arduino but without using current sensors. Any idea how to go about it??

You want to measure current without a current sensor? That's impossible. But probably you have some special current sensors in mind that you want to avoid. You have to specify which current sensors you want to avoid. Even a shunt resistor is a current sensor...

maybe a shunt resistor.

Measuring AC power current directly with an arduino via a shunt resistor is a very risky safety issue. Your really should use some form of isolation sensor such as a CT transformer of hall effect current sensor.

Lefty

http://www.vwlowen.co.uk/arduino/current/current.htm
but I don't know whats the purpose of the instrumentation amplifier and can the circuit be used for ac?

aryan007:
Measuring Current with the Arduino
but I don't know whats the purpose of the instrumentation amplifier and can the circuit be used for ac?

Note the note on that project page:

Circuits carrying Alternating Current have added complexity because the term resistance applies only to DC circuits. All circuits, have inductance and capacitance which are dependent on the frequency of the alternating current and which, when combined with the resistance of the circuit, result in the circuit's total impedance. For this simple tutorial, we'll stick with resistance and assume a DC circuit in which inductance and capacitance have no influence over Ohm's law.

Again for safety purposes please reconsider your desire to measure AC power current without using a good isolated current sensor.

Lefty

i can step down 240V to 12V using a simple step-down transformer but is there a way I can use shunt resistor for measuring ac?

aryan007:
i can step down 240V to 12V using a simple step-down transformer but is there a way I can use shunt resistor for measuring ac?

Sure there is but I'm of the opinion that if you have to ask such questions you shouldn't be working with AC power circuits. It's not personal, it's a policy thing with me.

Lefty

Sure there is but I'm of the opinion that if you have to ask such questions you shouldn't be working with AC power circuits. It's not personal, it's a policy thing with me.

Then how do I go about measuring ac using shunt resistor?

aryan007:

Sure there is but I'm of the opinion that if you have to ask such questions you shouldn't be working with AC power circuits. It's not personal, it's a policy thing with me.

Then how do I go about measuring ac using shunt resistor?

sigh<

If you could elaborate more on the shunt resistor method of ac measurement it would be greatly appreciated. Sorry for my stubbornness!

have to agree with lefty
if you have to ask - you shouldn't do it!

aryan007:
Hi ,
I want to measure 20A ac using arduino but without using current sensors. Any idea how to go about it??

My advice is not to try. Buy a 30A or 50A Hall current sensor, they don't cost much and they give you the isolation that you probably need.

Thank you all for the help, came across LEM LA-25NP current transducer.
I have attached it's datasheet but how do I connect it to my arduino

LA25-NP.pdf (83.2 KB)

I think you would find this http://uk.farnell.com/allegro-microsystems/acs712elctr-30a-t/ic-hall-effect-current-sensor/dp/1651975 easier to interface to an Arduino.

This is the safe way of using the shunt resistor method of ac measurement.

This is the safe way of using the shunt resistor method of ac measurement.

[/quote]I think you would find this http://uk.farnell.com/allegro-microsystems/acs712elctr-30a-t/ic-hall-effect-current-sensor/dp/1651975 easier to interface to an Arduino.[/quote]
Thank you all for the help looking forward to my project now!