# AC Current Sensing using UNO

#### y2jsh

Joined Oct 30, 2019
13
I am using a Current transformer to measure current from a source. Irrespective of the current i get knowing that i cannot give more than 5V to the Uno, i want to sense the current. I do not know how to go about it. I've thought of an approach that includes amplifying the current to a suitable value, converting to voltage and then the ac voltage to dc (or any change of order whichever is suitable). I am a college student with very little to no experience on this. So if i approach is correct, what are the components i can use that are not sensor modules, just ICs. If my approach is lengthy and if anyone knows a better way to do it, it would be of great help. Thank you.

This is the CT i am using

#### AlbertHall

Joined Jun 4, 2014
10,014

#### AlbertHall

Joined Jun 4, 2014
10,014

#### bertus

Joined Apr 5, 2008
20,566
Hello,

The ACHS712X is a hall effect sensor with linear output.
At 0 A the sensor shows about ½ Vcc.

Bertus

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#### y2jsh

Joined Oct 30, 2019
13
Hello,

The ACHS712X is a hall effect sensor with linear output.
At 0 A the sensor shows about ½ Vcc.

Bertus
I am getting a current of 0.25mA is all. So i will need a current amplifier to scale it up to alevel the Uno can read it accurately at right?

#### John P

Joined Oct 14, 2008
1,808
You're following the AAC tradition of treating the details of your project like a priceless secret. You said "measure current" and now you explain that the current is only 0.25mA.

AC or DC?
Is the source at a dangerous voltage?
Can you deal with this by putting a resistor in series with the current and then measuring the voltage across it?
What range does the current fluctuate through?
At what frequency?
What precision/accuracy must the measurement have?

Plus anything else that's important to someone thinking about the circuit.

#### y2jsh

Joined Oct 30, 2019
13
You're following the AAC tradition of treating the details of your project like a priceless secret. You said "measure current" and now you explain that the current is only 0.25mA.

AC or DC?
Is the source at a dangerous voltage?
Can you deal with this by putting a resistor in series with the current and then measuring the voltage across it?
What range does the current fluctuate through?
At what frequency?
What precision/accuracy must the measurement have?

Plus anything else that's important to someone thinking about the circuit.
The topic reads AC current sensing :|
And I'm testing it out with just the supply we get at our homes. 230V @ 50Hz. It's a 5A to 1.25mA CT. The current reading i got was 0.25mA from a multimeter. I have to read it from a MCU for other applications. And it is part of a product that will be launched, so secrecy is a given

Joined Jan 15, 2015
5,499
I would also suggest using an Allegro Fully Integrated, Hall-Effect-Based Linear Current Sensor IC solution. The ACS 712 is being phased out but the ACS 723 line offers some nice improvements. The ACS 723 offers up plenty of current ranges for AC and DC current. It is also very easily interfaced to an Arduino or similar uC. For initial testing there are several distributors offering the ACS 723 already mounted on a breakout board. Here is an overview of the different type breakout boards and interfacing to Arduino as well as some Arduino sample code.

You can build a circuit around a CT (Current Transformer) but using a hall effect current transformer is the better way to go.

Ron

#### ronsimpson

Joined Oct 7, 2019
705
The current reading i got was 0.25mA
The data sheet for the Current Transformer is not good. In one place it said 2000:1 ratio. So if you are reading .25mA X 2000 = 0.5A. But in another spot I think it said 5A in 1.25mA out which is a ratio of 4000:1.

Normally I put a "burden" resistor across the transformer and measure the voltage but the data sheet is not clear as to resistor value.