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 Post subject: Libelium 4-20mA shield with current sensor
PostPosted: Sat Jun 08, 2019 11:52 am 

Joined: Sat Jun 08, 2019 11:40 am
Posts: 7
Hi

I am using Seneca's T201DCH300-LP with the Libelium 4-20mA shield.
I connected 12V DC Gearbox37 (connects with 12V li-ion battery)through the current sensor, the Arduino shield reads only 4mA when i connect +ve of current sensor to +ve Vout and -ve of current sensor to +channel 4.

When i measure the current of motor through multimeter, it measures 0.098A, however it cant be measured with the current sensor. May I ask what is the problem?


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Mon Jun 10, 2019 9:02 am 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11289
Hi,

Could you please share with us an image or a schema of the connections?

Which code are you using to read with the 4-20mA board?

Regards


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Tue Jun 11, 2019 7:21 am 

Joined: Sat Jun 08, 2019 11:40 am
Posts: 7
This is the connections of the current sensor
https://www.seneca.it/en/linee-di-prodo ... dch300-lp/
I connect the followings:
- the -ve port of current sensor to +ve of channel 4 on libelium shield and
- the +ve port of current sensor to +ve of Vout on libelium shield

the Positive of 12V DC motor through the Seneca's current sensor and to +ve 12V battery
The negative of 12V DC motor to ground of battery


// Include this library for using current loop functions.
#include <currentLoop.h>

#define CHANNEL CHANNEL4

void setup()
{

// Switch ON the 24V DC-DC converter
sensorBoard.ON();

// Inits the Serial for viewing data in the serial monitor
Serial.begin(115200);
delay(100);
Serial.println("Arduino 4-20mA board switched ON...");
}

Read with the example code from the library of libelium board as followings:
void loop()
{
// Get the sensor value in int format (0-1023)
int value = sensorBoard.readChannel(CHANNEL);
Serial.print("Int value read from channel 4 : ");
Serial.println(value);

// Get the sensor value as a voltage in Volts
float voltage = sensorBoard.readVoltage(CHANNEL);
Serial.print("Voltage value rad from channel 4 : ");
Serial.print(voltage);
Serial.println("V");

// Get the sensor value as a curren in mA
float current = sensorBoard.readCurrent(CHANNEL);
Serial.print("Current value read from channel 4 : ");
Serial.print(current);
Serial.println("mA");


Serial.println("***************************************");
Serial.print("\n");

delay(2000);
}


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Tue Jun 11, 2019 1:21 pm 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11289
H,

Do you have the same behaviour with or without the jumper of the channel 4?

Regards


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Wed Jun 12, 2019 3:42 am 

Joined: Sat Jun 08, 2019 11:40 am
Posts: 7
i didnt try with the jumper at channel 4.
What is the purpose of jumper of channel 4 and what does it connect to?

And the result shown on Arduino serial monitor shows value between 4 to 20mA and does not convert to the actual current value?


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Wed Jun 12, 2019 12:14 pm 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11289
Hi,

Your sensor should work without the jumper of channel 4 due to is a sensor type 4.

The output of the code will be always between 4 and 20mA, then the user should make the conversion to the desired unit depending on the sensor attached to the board.

Do you see any change in the output when you are sensing something or when is empty?

Regards


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Fri Jun 14, 2019 2:43 am 

Joined: Sat Jun 08, 2019 11:40 am
Posts: 7
Hi there,

I got it to work by sensing a stepper motor NEMA 17 instead of 12V DC motor.
I think 0.098A from the 12V DC motor is too small for Seneca sensor to observe the change.
The current of running NEMA 17 is 4.06mA and 4.00mA when the stepper motor is off.


If I can consult you on some theory on stepper motor? May I know if the current value of stepper motor will increase if I add resistance (trying to stop) on the stepper motor?


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Mon Jun 17, 2019 7:01 am 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11289
Hi,

Which output do you get when the 12V DC motor is ON?

Regarding your question, yes the current should increase if you add resistance to the stepper motor.

Regards


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Tue Jun 18, 2019 5:56 pm 

Joined: Sat Jun 08, 2019 11:40 am
Posts: 7
I get 4.00mA when I turn on my 12V DC motor. Is fine for the issue of DC motor, cause i realised i need to retrieve current from AC 3 phase motor.
The resistance i am meaning external force in reverse direction of the AC 3 phase motor or stepper motor


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 Post subject: Re: Libelium 4-20mA shield with current sensor
PostPosted: Thu Jun 20, 2019 9:01 am 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11289
Yes, as we said if you apply external force in reverse direction the current should increase.

Regards


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