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Author: MIKROE
Last Updated: 2024-10-31
Package Version: 2.1.0.6
mikroSDK Library: 2.0.0.0
Category: Measurements
Downloaded: 76 times
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License: MIT license
Wheatstone Click is a measurement Click board™ which utilizes a Wheatstone bridge circuit onboard, in order to precisely measure the resistance of an external element. Besides the wheatstone bridge circuit, this Click board™ also utilizes MAX4208 – an ultra-low offset/drift, precision instrumentation amplifier, from Maxim Integrated.
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DOWNLOAD LINK | RELATED COMPILER | CONTAINS |
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5390_wheatstone_click.zip [283.23KB] | mikroC AI for ARM GCC for ARM Clang for ARM mikroC AI for PIC mikroC AI for PIC32 XC32 GCC for RISC-V Clang for RISC-V mikroC AI for AVR mikroC AI for dsPIC XC16 |
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Wheatstone Click is a measurement Click board™ which utilizes a Wheatstone bridge circuit onboard, in order to precisely measure the resistance of an external element. Besides the wheatstone bridge circuit, this Click board™ also utilizes MAX4208 – an ultra-low offset/drift, precision instrumentation amplifier, from Maxim Integrated.
We provide a library for the Wheatstone Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.
Package can be downloaded/installed directly form compilers IDE(recommended way), or downloaded from our LibStock, or found on mikroE github account.
This library contains API for Wheatstone Click driver.
wheatstone_cfg_setup
Config Object Initialization function.
void wheatstone_cfg_setup ( wheatstone_cfg_t *cfg );
wheatstone_init
Initialization function.
err_t wheatstone_init ( wheatstone_t *ctx, wheatstone_cfg_t *cfg );
wheatstone_set_potentiometer
Set potentiometer ( 0 - 100k )
void wheatstone_set_potentiometer ( wheatstone_t *ctx, uint8_t pot_value );
wheatstone_read_an_pin_voltage
This function reads results of AD conversion of the AN pin and converts them to proportional voltage level.
err_t wheatstone_read_an_pin_voltage ( wheatstone_t *ctx, float *data_out );
This example demonstrates the use of Wheatstone Click board by measuring the input resistance.
The demo application is composed of two sections :
Initializes the driver and logger and sets the default potentiometer (gain) level.
void application_init ( void )
{
log_cfg_t log_cfg;
wheatstone_cfg_t cfg;
/**
* Logger initialization.
* Default baud rate: 115200
* Default log level: LOG_LEVEL_DEBUG
* @note If USB_UART_RX and USB_UART_TX
* are defined as HAL_PIN_NC, you will
* need to define them manually for log to work.
* See @b LOG_MAP_USB_UART macro definition for detailed explanation.
*/
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_info( &logger, " Application Init " );
// Click initialization.
wheatstone_cfg_setup( &cfg );
WHEATSTONE_MAP_MIKROBUS( cfg, MIKROBUS_1 );
wheatstone_init( &wheatstone, &cfg );
wheatstone_set_potentiometer ( &wheatstone, WHEATSTONE_POT_MAX );
log_info( &logger, " Application Task " );
}
Reads the AN pin voltage and calculates the input resistance from it. All data are being displayed on the USB UART where you can track their changes.
void application_task ( void )
{
float an_pin_v = 0;
float vout = 0;
float r_kohm = 0;
if ( WHEATSTONE_OK == wheatstone_read_an_pin_voltage ( &wheatstone, &an_pin_v ) )
{
vout = an_pin_v / wheatstone.gain;
if ( 0 != vout )
{
r_kohm = ( WHEATSTONE_VCC_5V - 2 * vout ) / ( 4 * vout );
}
log_printf( &logger, " VCC : %.3f V\r\n", WHEATSTONE_VCC_5V );
log_printf( &logger, " GAIN : %.3f\r\n", wheatstone.gain );
log_printf( &logger, " AN_PIN : %.3f V\r\n", an_pin_v );
log_printf( &logger, " VOUT : %.3f V\r\n", vout );
log_printf( &logger, " R_INPUT : %.3f kOhm\r\n\n", r_kohm );
Delay_ms ( 1000 );
}
}
The following formulas you may find useful:
- AN_PIN(V) = ( ( 1kOhm + R_INPUT(kOhm) ) / ( 1kOhm + 2R_INPUT(kOhm) ) - 1/2 ) VCC(V) * GAIN
- VOUT(V) = AN_PIN(V) / GAIN
- R_INPUT(kOhm) = ( VCC(V) GAIN - 2AN_PIN(V) ) / ( 4*AN_PIN(V) )
- R_INPUT(kOhm) = ( VCC(V) - 2VOUT(V) ) / ( 4VOUT(V) )
The full application code, and ready to use projects can be installed directly form compilers IDE(recommneded) or found on LibStock page or mikroE GitHub accaunt.
Other mikroE Libraries used in the example:
Additional notes and informations
Depending on the development board you are using, you may need USB UART Click, USB UART 2 Click or RS232 Click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all Mikroelektronika compilers, or any other terminal application of your choice, can be used to read the message.