Voltmeter click
Voltmeter click is a mikroBUS™ add-on board for measuring voltage in an
external electric circuit.
The board is designed to measure Direct Current only, and has a measurement
range from 0 to 24V (it’s possible to measure both positive and negative
charges).
The design of the board is based on an OpAmp set up as a differential amplifier
with a buffered input.
Two onboard screw terminals (probe+ and probe-) are bringing in the current,
which then flows through a row of four resistors. A voltage – proportional to the
input charge – is generated across the last two resistors. From there it is sent
to the differential amplifier that further intensifies the difference between the
two inputs (+/-).
The resulting charge is exactly 33 times lower than the actual measured
voltage. It is converted by an onboard 12-bit ADC before being outputted
through the mikroBUS™ SPI interface (the firmware in the target board MCU
should be set up to multiply the ADC value to get the actual voltage). It is also
possible to output the analog value directly through the mikroBUS™ AN pin
(useful if the target MCU has a higher resolution ADC).
The board can work with either a 3.3V or a 5V power supply.
Technical Specifications
Applications
Measuring DC Voltage from external circuit
Key features
Measurement range: 0-24Vdc
12-bit ADC
SPI interface (+ AN pin)
3.3V or 5V power supply
Key Benefits
Measures both positive and negative charges
Possible to measure analog values directly
Works in all mikroC compilers
Ready-to-use examples save development time
mikroBUS™ is specially designed pinout standard with SPI, I2C, Analog, UART, Interrupt, PWM, Reset and Power
supply pins. See Standard Specification.
Programming
The following code snippet shows how to send temperature readings from Voltmeter click to a TFT display. .
1 void system_setup( void );
2 unsigned int getADC( void );
3
4 void main()
5{
6 system_setup();
7
8 while (1)
9 {
10
11 voltage = 0;
12
13 measurement = getADC() / 2; // Get ADC result
14 voltage = (measurement - calibration) * 33.3405;
15
16 FloatToStr(voltage, txt);
17
18
UART1_Write_Text(txt);
19 UART1_Write(32);
20 UART1_Write_Text("mV");
21 UART1_Write(13);
22 UART1_Write(10);
23
24 delay_ms(1000);
25 }
26 }
27
28 void system_setup( void )
29 {
30 GPIO_Digital_Output( &GPIOD_BASE, _GPIO_PINMASK_13 );
31
32 UART1_Init(9600);
// Initialize UART module at 9600 bps
33 Delay_ms(300);
// Wait for UART module to stabilize
34 UART1_Write_Text( "UART Initialized\r\n" );
35
36 voltage = 0;
37 sum = 0;
38 measurement = 0;
39 calibration = 0;
40
41 Chip_Select = 1;
42
43 // SPI
44 SPI3_Init_Advanced( _SPI_FPCLK_DIV16, _SPI_MASTER | _SPI_8_BIT |
45
_SPI_CLK_IDLE_LOW | _SPI_SECOND_CLK_EDGE_TRANSITION |
46
_SPI_MSB_FIRST | _SPI_SS_DISABLE | _SPI_SSM_ENABLE |
47
_SPI_SSI_1, &_GPIO_MODULE_SPI3_PC10_11_12 );
48 Delay_ms(300);
49 UART1_Write_Text( "SPI Initialized\r\n" );
50
51 calibration = getADC() / 2;
52 }
Code examples that demonstrate the usage of Voltmeter click with MikroElektronika hardware, written for
mikroC for ARM, AVR, dsPIC, FT90x, PIC and PIC32 are available on Libstock.
MIKROE-2436
Voltmeter click
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