Hello, I need help about measuring Ac Voltage. How can I measure AC voltage by using Arduino? Do I need any additional IC? Is it possible to measure small voltages? Do I need to transform AC to DC for measurement?
Thanks
- How can I measure AC voltage by using Arduino?: you need a sensor; you cannot directly conect AC to arduino (roughly speaking . . . .)
Do I need any additional IC?: Yes, or, at least some components (rectifier, capacitor . .)
Is it possible to measure small voltages?: How small?
Do I need to transform AC to DC for measurement?: Yes and no; what's the scenario?
Thanks: you're welcome.
Regards
vffgaston:
- How can I measure AC voltage by using Arduino?: you need a sensor; you cannot directly conect AC to arduino (roughly speaking . . . .)
Do I need any additional IC?: Yes, or, at least some components (rectifier, capacitor . .)
Is it possible to measure small voltages?: How small?
Do I need to transform AC to DC for measurement?: Yes and no; what's the scenario?
Thanks: you're welcome.
Regards
Ok I am trying to make a smart outlet that measures the power usage of the device that plugged to it. So in order to measure power I will measure the current drained by the device. Then according to formula (W=V*I), that current will be multiplied with 220V.
In order to measure the current, I will put a small resistor (about 0.22Ohm) between input voltage and output then i will measure voltage on that resistor. I am planning to use Arduino Nano.
Thanks
OK. So what you need is measuring AC current.
I will put a small resistor (about 0.22Ohm) between input voltage and output
I don't recommend you doing so. This would connect the arduino to the mains (to one of the two poles); I don't remember how english (US) do it -earthing mains, I mean-, but, whatever they/you do it, it's (very) dangerous.
It looks like you want to experiment a bit (checking Ohm's law and so on): this is healty. You can use a current transformer: this device "generates" a current that is proportional to the one you want to measure and isolates you from the other -mains- circuit (google "current transformer"). It only works with AC current and generates AC current too.
You're rigth: if you connect this (AC current) to a resistor, you will have AC voltage proportional to the current you want to measure.
We are again at the beginning: you cannot (roughly speaking) conect this AC voltage to the arduino. The best would be to rectify this AC voltage and measure the rectified DC voltage (that would be proportional to the AC voltage that is proportional to the AC current you want to measure).
Of course you have some options to directly measure the AC current: "http://www.amazon.es/Vivian-Current-Sensor-Arduino-ACS712T/dp/B0156FWC0O/ref=sr_1_10?ie=UTF8&qid=1444315042&sr=8-10&keywords=arduino+hall+sensor"
Regards
To avoid electrocution, use a current transformer instead of a resistor.
vffgaston:
It looks like you want to experiment a bit (checking Ohm's law and so on): this is healty. You can use a current transformer: this device "generates" a current that is proportional to the one you want to measure and isolates you from the other -mains- circuit (google "current transformer"). It only works with AC current and generates AC current too.Regards
So, is that what I should do:
I will use current transformer for reducing current then use a diode bridge to transform into DC. Then measure the DC voltage with Arduino.
I considered using transformer but couldnt decide to a suitable one. Can you suggest me a proper one.
Should I use a resistor for transformed current? (In order to have a measurable voltage)
Thanks
raschemmel:
Low Current sensor
Thank you so much
raschemmel:
Low Current sensor
Note that if you use a current transformer, as suggested by rashemmel, then you need to connect an external "burden resistor" as mentioned in the datasheet.
Failure to do this will result in the current transformer giving out a dangerous voltage, as the transformer tries to drive a current through an open circuit.
There is some useful information about using a current transformer with an Arduino, here.
This sensor does not have a load resistor built in, so in most cases it will be necessary to place a resistor across the output to convert the coil’s induced current to a very small measurable voltage.
I will use current transformer for reducing current then use a diode bridge to transform into DC. Then measure the DC voltage with Arduino.
This would give you a double wave rectifier ("Google").
The rectified double wave current passed through a resistor gives you a voltage shaped this way (double wave). This is DC, but not "constant" DC; if you connect this to arduino directly it would be farragous measuring it , for you would have to sample the signal to then calculate the RMS value . . . a theoretical exercise far from your knolewdge (and mine one; I don't know even if this is feasible at commercial frequencies -50/60 Hz- with an arduino).
The simplest solution is to filter the AC double wave voltage signal by means of a RC filter; for an small -reccomended- resistor connected to the bridge (you can, even, shorcircuit it. this is a theroretical consideration: you need a resistor) like the one you told in your first post, a RC filter with a 10 kOhm / 1 uF will give reasonable response time and a sufficient precise measure (and yes, you can connect it to the arduino).
Regards
Wouldn't he need to bias it at 2.5 V with a divide by 2 voltage divider ? (two 10 k ohm resistors)