View source for Lesson 30--Microduino-made DC V-A Meter

Using Microduino to Make a DC V-A Meter--C# PC Display  
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==Purpose==
The tutorial uses Microduino to make a DC V-A meter. The PC-side upper computer Winform can display the voltage and current values being measured. From the tutorial, you can have a further understanding of operational amplifier as well C# program example, and also get prepare for flexible application of Microduino and the real circuit buildup.    
==Equipment==
*'''[[Microduino-Core]]'''
Microduino-Core is the 8-bit single-chip development core board with Atmel ATmega328P as the core, which is an open and Arduino Uno compatible controller. 

*'''[[Microduino-USBTTL]]'''
Microduino-USBTTL is the program download module, capable of connecting with Microduino-Core or Microduino-Core+ and making the modules communicate with the computer. It uses MicUSB as the download interface, which is also the smallest part of Microduino.  Microduino is just as small as a quarter. Besides, the download cable is just like the USB cable of most smart phones, easy to use.  
  
*Other Hardware Equipment
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|Related hardware||Number||Function 
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|LM358||One||A common dual operational amplifier, it is convenient for you to achieve mathematical operation circuit.  
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|ICL7660||One||Negative pressure-generated chip, used for operational amplifier power supply.  
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|AD620||One||Instrument amplifier, used for current detection.  
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|1/4W Ω resistor||Several||Check the schematic.  
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|0.01 Ω resistor(5W) ||One||Cascaded in the circuit being measured.   
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|1 Ω resistor(10W)||One||Cascaded with 0.01 Ω resistor and then connected to dry battery for testing current.  
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|10uF 16V aluminum electrolytic capacitor||Three||For negative pressure generation circuit.   
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|Dry battery ||Several||For testing.  

|USB cable ||One||For connecting Microduino modules and PC.  
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|Breadboard ||One ||All components gather here.  
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|Jumper ||One box ||Served as the connector.    
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===AD620 Instrument Amplifier===
AD620 instrument amplifier is the product of AD company in America. Users can set the gain of any request from 1 to 1,000 with only an external resistor. Here we adopt a 2K Ω external resistor, meaning the gain G=1+（49.4/2）=25.7. 
The core of AD620 instrument amplifier is the three-stage operational amplifier circuit, which has higher CMRR(Common Mode Rejection Ratio) and a good temperature stability as well as small noise factor and high accuracy.   


==Schematic==
[[File: IV_Control_protelSch.jpg|600px|center|thumb]]
The circuit can test the current within 19.45A and the voltage within 50V theoretically.   
*Computing method of current: 25.7(Gain)*0.01(Resistance)*I(Current)<5V and here we get ”I<19.45A”. (Note: The cross-sectional area of the current connector should be no less than 2.5 mm².)
*Computing method of voltage: The output voltage of LM358 cannot be higher than 5V(Power supply). Since the input voltage is reduced to 0.1 time of the original voltage, the theoretical test voltage is 50V.  

==Program==

<source lang="cpp">
int myValueA0_V=0;//for  measure  voltage
int myValueA5_I=0;//for  measure  current
void setup()
{
  Serial.begin(9600);
}
void loop()
{
  myValueA0_V=analogRead(A0);
  delay(10);
  Serial.print(myValueA0_V*5.0/1023,3);
  Serial.print('\n');//C#  program need this character to split 
  myValueA5_I=analogRead(A5);
  delay(10);
  Serial.print(myValueA5_I*5.0/1023,3);
  delay(300);//send data delay     fit for  c# program time_tick
}
</source>

==Debugging==
*Make sure the connection is all right. 
*Copy the program to Arduino IDE.  
*Compile the program and choose the right board and the related serial port. 
*Click Upload. 
*Open the file IV_control\bin\Debug under the folder of IV_control.exe after uploading Arduino program, you can see the form interface. (The C# program is supported by".NET framework 4.0" . ) 
*Let's begin testing. Just watch the value change of the current and voltage in the form interface.  

[[File:IV_Control_comOutput.jpg|600px|center|thumb]]
*Images of C# source program, Microduino and the protel schematic is available for download.    
Csharp program and picture: '''[[File:Csharp program and pictures.rar]]'''

==Result==
Watch current and voltage values and compare them with the theoretical value. 
==Video==
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