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1  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
2  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
3  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 )-:
4  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?
5  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??
6  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
7  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?
8  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
9  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
10  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
11  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
12  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
13  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
14  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
15  Using Arduino / Microcontrollers / Re: load sketch to stand alone atmega328p-pu chip on: April 18, 2013, 02:06:44 pm
When testing the FTDI board no sketch is involved, you are not talking to any Arduino.  You are creating a loopback so whatever goes out the Tx pin should be picked back up on the Rx pin.  Just use the Arduino IDE and select the Serial port and then open the Serial Monitor.  Type some characters and press the Send button.  If the same characters show back up in the window below the entry line then your FTDI board is working fine.

The baud rate of the chip will be whatever the bootloader is configured to run at.  For Optiboot it should be 115200 baud.  This is what the Uno board selection is using.  The IDE will adjust the baud rate of the FTDI based on which Board you select.  So if you selected the wrong board type, say Duemilanove then the IDE will try to use 57600 baud on the FTDI board, and will not match up to the chip bootloader running at 115200 baud.  So board selection is important and needs to match up to the bootloader type.



O.k I got it, thanks.
If I used Nicks gammon bootloader do you know the baud rate ?
Etay
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