Hi,
I am new to Arduino and electronics.I have Arduino Mega 2560 and I want to create a small college project.
So I have an electrical circuit made of resistors,capacitors,LED's,etc.And in that circuit there is a current and a voltage.
I need to measure the value of the voltage and the current and send the data to Arduino.
Can you please tell me what tools/equipment do I need and how can I connect all of them.
Thank you!
Connect arduino ground to project ground.
If the voltage being measured is under 5v (3.3v if you had a Due or 3.3v pro mini, instead of the mega which is 5v), you can measure the voltage directly with the ADC.
If the voltage being measured is higher, you'll need to use a pair of resistors as a voltage divider to get the voltage below the operating voltage of the Arduino.
For current, put a low-value resistor in series with the load, and measure the voltage drop across the resistor. You may want to use the ADC in differential mode for this.
Hi,thank you for the repply.
So if I have a 4V signal I can connect the ADC (analog to digital converter) dirrectly to an analog pin on my arduino board?
And also can you please make a montage,such as :
electrical circuit->ADC->resistors->Arduino
So if I have a 4V signal I can connect the ADC (analog to digital converter) dirrectly to an analog pin on my arduino board?
Yes. The analog input can be up to Vcc (usually 5V).
At more than 5V (technically, more than Vcc) you can damage the Arduino.
The 10-bit ADC will read full-scale (1023) when the input is equal to the reference. The default reference is Vcc. There is optional 1.1V internal reference, or you can connect an external refernce (of 5V or less).
With the default 5V reference, 4V will read (4/5) x 1023 = 818 (approximately). Of course, you can use the fixed proportional relationship between the ADC count and 5V in your software to get voltage.
Measuring current is somewhat tricky. Do you know how to do it with a multimeter? Do you have a schematic for the circuit you are measuring? There might be a way to measure the voltage across one or more resistors, and have your Arduino sketch calculate the current from that. (If you are an Electrical Engineering student, I assume you know how to apply Ohm's Law and Kirchhoff's Law... If you are majoring in something else, you may need some help with that.)
Otherwise, you'll have to put a known small-value resistor in series, "float" the Arduino's ground, and measure the voltage across that resistor to calculate the current.
Of course, that added resistor will add to the total resistance and change the actual current flowing in the circuit... That's why the added resistor should be "small" (have a low resistance value). And since the voltage drop that added low-value resistor will he low, you may want to use the 1.1V reference.
Can you please explain to me,or give me a schematic on how to measure the value of the current/voltage using a multimetter?
Thanks.
I think we can safely assume he/she is not a EE major.
I am sure you have used YouTube.
Lots of small tutorials there.
https://m.youtube.com/results?q=current%20measurement&sm=1
pegwatcher:
I think we can safely assume he/she is not a EE major.
Don't count on it. I witnessed an EE grad, first day on the job, first assignment was to measure the voltage of a battery with a DVM. Put only one probe to one side of the battery and had to be told to connect the other one to the other side. I kid you not.
I haven't expressed myself correctly.I know how to use a multimeter,the main problem is the next one:
I have the circuit,I connect the multimeter to it,I measure the current value,but how do I send the data to Arduino.
idea#1:
electrical circuit ->multimeter->ADC->some resistors to limit the current & the voltage ->arduino.
Is that ok?Far as I read is that the arduino has an inbuilt ADC,if that's true I don't have to use and external one.
Thanks.
In your example, what is the multimeter doing for you? Most have an LCD screen and no output that a user can access. You can get a meter with a serial output, example:
Then all you need is RS232 to TTL adapter
http://www.nkcelectronics.com/rs232-to-ttl-converter-board-33v232335.html
or
http://www.nkcelectronics.com/RS232-to-TTL-converter-board-DTE-with-Male-DB9-33V-to-5V_p_369.html
Arduino does have an ADC, you can apply 0 to 5V to the inputs with Vcc = 5V.
What is the voltage you want to measure?
Hi CrossRoads,
In my example my multimeter should measure the current from a circuit connected to a 230V or higher power supply and send the data to the arduino.
I have what I need for this project,the problem is how in the world I'm gonna hook them up,that's it.I need a scheme or something like that.
230V AC or DC?
Usual way to measure something like that is to put a shunt resistor in series, and measure the voltage across the resistor.
If one leg of the resistor goes to Gnd and the voltage is only positive, that's easy.
Another way is to use a sensor that goes around the wire and outputs a voltage you can measure.
http://www.digikey.com/product-search/en/transformers/current-sense-transformers/786724?k=current%20sensor
Another way is to use a sensor that uses current flow to induce a change in a wire placed next to the current carrying wire. I drawing a blank as to what those are called tho.
A part like this
I don't know who makes one as finished module/probe/etc tho.
Or I can make something that measures the voltage in the circuit and apply Ohm's law and get the value of the current.
Can you please tell me if this logic is correct:
Electrical Circuit->Voltmeter->ADC->Resistors->Arduino
Thanks.
Electrical Circuit->Resistor1 - Resistor - Gnd
^ Arduino ^ connects here & here.
Or
Electrical Circuit->Shunt - Gnd
^ Arduino ^ connects here & here.
Shunt is really resistance, so High voltage, low resistance means the shunt doesn't impact the circuit much.
Then Ohms Law as you said
V=IR, I = V/R. Arduino can measure V (as a reading from 0 to 1023, about 4.88mV per bit increment), you know R, do the math.
Thank you CrossRoads!
230V current in an AC circuit? I'd use a hall effect current sensor. You get complete isolation and the output is scaled to 0-5V. The output should be at 2.5V with zero current, then it goes above or below depending on direction.
geniulmalefic:
Can you please explain to me,or give me a schematic on how to measure the value of the current/voltage using a multimetter?
Thanks.
below is a good place to start.
You can use instrument transformers if you are measuring high voltage and high currents..
I think we can safely assume he/she is not a EE major.
I think we can also safely assume they don't like to do their own homework.
I have the circuit,I connect the multimeter to it,I measure the current value,but how do I send the data to Arduino.
Draw the schematic of your circuit and post a photo of it. You're a college student so I assume you know how to draw a schematic.
FYI, the multimeter is test equipment . It's not part of your arduino interface. The meter + Ohm's Law should tell you everything you need to know. The voltage can be measured with a voltage divider and the current with a CT (current transformer)
CT