Speed Sense Click

How does it work?

Speed Sense Click is based on the A17501, a dual output differential speed and direction sensor from Allegro Microsystems. The sensor consists of three Hall elements incorporated in such a way as to create two independent differential channels. The differential signals are used to produce a highly accurate speed output and, if desired, provide information on the direction of rotation. The advanced self-calibration technique with the digital tracking of the signal results in accurate switch points over the air gap, speed, and temperature. The sensor is immune to common external magnetic disturbance and is ideally suited for asynchronous electric motor applications.

When properly back-biased, the sensor is intended for use with ring magnets or ferromagnetic targets. It poses a temperature-compensated amplifier, as well as a full-range ADC. Besides operating on 5V from the mikroBUS™ socket power rail, you can also add an external power supply over the VEXT connector from 4 up to 24V. The selection can be made over the VIN SEL.

Speed Sense Click uses general-purpose IOs to interrupt the host MCU when detecting the magnet on a spinning wheel. The output channel pins are labeled CHA and CHB. There is also an external header with these channels for connecting an external device (relay, LED, and more).

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Specifications

Pinout diagram

This table shows how the pinout on Speed Sense Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Channel B Output	CHB	1	AN	PWM	16	NC
	NC	2	RST	INT	15	CHA	Channel A Output
ID COMM	CS	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Speed Sense Click electrical specifications

Software Support

We provide a library for the Speed Sense Click as well as a demo application (example), developed using MIKROE compilers. The demo can run on all the main MIKROE development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for Speed Sense Click driver.

Key functions

• speedsense_get_speed This function reads the state of the CHA pin used for speed output protocols.

• speedsense_get_direction This function reads the state of the CHB pin used for direction output protocols.

Example Description

This library contains the API for the Speed Sense Click driver for the speed and direction signal state detection for every magnetic pole pair.

void application_task ( void )  
 { 
     uint8_t direction = 0, speed = 0; 
     speed = speedsense_get_speed( &speedsense ); 
     direction = speedsense_get_direction( &speedsense ); 

     if ( start_measure & speed ) 
     { 
         signal_duration = time_cnt - start_timer; 
         start_timer = time_cnt; 

         if ( SPEEDSENSE_DIR_STATE_FWD == direction ) 
         { 
             log_printf( &logger, " Direction: Forwardrn" ); 
         } 
         else 
         { 
             log_printf( &logger, " Direction: Reversern" ); 
         } 
         log_printf( &logger, " Speed: %.2f rpmrn", SPEEDSENSE_CALC_RMP / signal_duration ); 
         log_printf( &logger, " Duration: %lu msrn", signal_duration ); 
         log_printf( &logger, " Time: %lu  msrn", time_cnt ); 
         log_printf( &logger, "-----------------------rn" ); 
         start_measure = SPEEDSENSE_STOP_MEASURE; 
     } 
     else if ( ( !start_measure ) & ( !speed ) ) 
     { 
         start_measure = SPEEDSENSE_START_NEW_MEASURE; 
     } 

     time_cnt++; 
     Delay_ms( 1 ); 
 }

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended), downloaded from our LibStock™ or found on Mikroe github account.

Other Mikroe Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.SpeedSense

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. UART terminal is available in all MIKROE compilers.

mikroSDK

This Click board™ is supported with mikroSDK – MIKROE Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.