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1  Topics / Education and Teaching / question regarding arduino eagle files on: July 15, 2014, 04:06:40 pm
Hello,
i didn't know where to put this question. hope this is the right place.
i looked at the arduino smd files and i attache zoom in on the atmega328 package.
the layer t-stop has some overlap between the pads. this means that all the pads will be short no?
or i don't understand exactly what this t-stop layer does.
can somebody please help me with this?
thanks,
Etay
2  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: November 12, 2013, 04:27:43 pm
Hi UnoDueTre,
you are right.
i connected pin 3 to grond and reduced the peak of the sine wave to 100 mV but still same output of around 300mV
maybe something is wrong in the simulaiton. i'll try to connect the chip on breadboard see what happen :-)
Etay
3  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: November 09, 2013, 10:56:47 am
Hey UnoDueTre,
do you have some experience in rms do dc?
i just simulated the circuit you proposed with multisim software (attached picture of the circuit)
the output is very law and nos as expected.
do you know what seems to be the problem?
regarding your question, yes i know its negative. i think of using inverter to get it positive
thanks,
Etay
4  Using Arduino / Installation & Troubleshooting / Re: arduino doesn't appear on Device Manager on: November 08, 2013, 03:35:21 pm
Very strange indeed!!
I tried to connect it to different computer I have and also there nothing happened on the device manager.
The orange led blinked several times and then stays Off. ( same behavior when I connect the my old Uno)
I thought maybe the data pins inside the USB port on the board are not with contact with the cable...
What else can be?
Pretty annoying because it's brand new board )-:
5  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: November 08, 2013, 02:01:16 pm
Hello UnoDueTre,
I saw this chip.
Now I have AD737 from analog digital. Do you some experience with it?
6  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: November 08, 2013, 01:35:51 pm
Hi MarkT,
I agree with you. So now arise the question how to calculate the rms value??
7  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: November 08, 2013, 12:16:07 pm
Hello again,
i measured using scope the voltage on the shunt resistor and i was puzzled because the current is not sine wave!
you can see in the picture the wave form on the scope.
the problem with this wave form is that taking the peak and divide by sqrt of two wont give me the real rms value...
what do you think?
it seems i need to use some kind of rms to dc chip no?
thanks,
Etay
8  Using Arduino / Installation & Troubleshooting / Re: arduino doesn't appear on Device Manager on: November 08, 2013, 04:16:22 am
Yes it's new and original. I bought it on amazon.
Actually when I connected it for the first time it appeared on the device manager and I even loaded the blink code on it but then for sone reason when I tried to upload other sketch the it said that Com3 is used by other program so I tried to disconnect the board from the usb but when I reconnected it nothing happened, meaning it doesn't appear even on the device manager.
Maybe something went wrong on the board?
9  Using Arduino / Installation & Troubleshooting / Re: arduino doesn't appear on Device Manager on: November 08, 2013, 02:07:45 am
Hey  MasterPi,
Here are the full ( I hope..) data:
When I connect the new arduino to the computer nothing happened. No sound and nothing on the device manager. But the board does get power, the green ON led is on
But when I connect my old one everything works fine.
What do you think?
Best wishes,
Etay
10  Using Arduino / Installation & Troubleshooting / arduino doesn't appear on Device Manager on: November 07, 2013, 01:33:32 pm
Hello,
i just got my new R3 uno board but when i connect it the computer doesn't seems to recognize it...
this is strange because with the same cable when i connect my old r3 uno board everything works just fine.
any idea?
thanks,
Etay
11  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: October 12, 2013, 01:02:55 pm
O.k thanks.
I have some op amp at my work.
Ill try to do as you said and will post here my result
Thank you very much,
Ety
12  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: October 11, 2013, 03:28:04 pm
The time constant is 1.5k*10u=15ms no?
You. Used the same circuit also for current sensing from 50 hz grid?
Shouldn't I aim exactly for 20ms I'm integration time?
Thanks very much for your help,
Etay
13  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: October 11, 2013, 11:09:07 am
O.k
Your circuit looks like integrator and rectifier is that right?
The capacitor and the 1.5k are the time constant of the integrator and  the 1.5k and 62k is the amplification
14  Using Arduino / Project Guidance / Re: measuring current with Current transformer on: October 11, 2013, 09:44:51 am
Hey Jremington,
Thanks for the advice. Actually I though this might the problem...
When using your propose circuit I'll get rectified signal so still I'll need to calculate RMS value  so the loop will look the same no?
Thanks,
Eray
15  Using Arduino / Project Guidance / measuring current with Current transformer on: October 10, 2013, 03:53:26 pm
Hello,
i'm trying to build energy cosmuption monitor for my home. here we have 220V@50Hz
i red about CT and bought some from sparkfun.
basically i read the voltage across some load resistor and from that i can calculate the secendory current (I=V/RLoad)
from the turn ratio (2000) i can deduce the primery current.
here is my code:
Code:
  int SensorValue = 0;
  int WireTurns = 2000;  // the ratio between I primery and I secondary
  int Num_of_Samp = 500;
  int DelayMicros = 20000/Num_of_Samp; // 1/50Hz is 20ms period
  float Rload = 2000.0/(float)WireTurns;
  float volt = 0;
  float RMS = 0;
  float I=0;

void setup() {
  Serial.begin(115200);
}

void loop() {
  RMS = 0; 
    for (int ii=0;ii<Num_of_Samp;ii++){
        SensorValue = analogRead(A0);
        volt = 0.00489*SensorValue; //  5/1023 = 4.88mV
        volt = volt-2.5;
        volt = volt*volt;
        RMS = RMS + volt;
        delayMicroseconds(DelayMicros);     
    }
    RMS = RMS/(float)Num_of_Samp;
    RMS = sqrt(RMS); 
    I = RMS/Rload;

    Serial.print("Max Voltage:");
    Serial.print((RMS*1.44)+2.5);
    Serial.print(" RMS current:");
    Serial.print(I);
    Serial.print(" Power cons.:");
    Serial.println(I*220);
}

i read the voltage 500 times, calculate the square value and finaly after the loop ends i take the mean and then the square.
here is my problem:
i get different RMs current reading when using different resistors.
when using 5K ohm i get 0.16A and when using 2k ohm i get 0.22 A
anybody here tried doing something like this?
thanks,
Etay
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