Localizador de distância baseado em AT89S52 e sensores ultrassônicos HC-SR04

Distance finder based on AT89S52 and HC-SR04 ultrasonic sensors

Distance finder based on HC-SR04 gives the distance to an obstacle in centimeters. It has a range of 2 cm to 400 cm. The project is built around the AT89S52, which is a microcontroller from the 8051 family. Distance is displayed on seven-segment displays.

Components:

AT89S52

Three 7 seconds. Expense (Common anode type)

HC-SR04 (ultrasonic sensor module)

Connectors, PCBs etc.

The code is written in Assembly and is easily understandable. The project can be used in robots to avoid obstacles, etc.

Working:

The operation of ultrasonic sensors is quite simple and easy to interface with the microcontroller. The sensor module has 4 pins, of which Pin-1 and Pin-4 are +Vcc and Gnd respectively. Pin-2 is Trigger and Pin-3 is Echo pin.

When a high pulse of 10us is applied to the TRIG pin, the ultrasonic transmitter sends 8 consecutive pulses of 40kHz frequency. As the eighth pulse is sent, the sensor's ECHO pin becomes HIGH. Now when ultrasonic waves are reflected from any surface and are received by the receiver, the ECHO pin goes LOW. The time it takes to leave and return to the sensor is used to find the distance to the reflecting surface.

Distance in centimeters = (Time/58) cms

In inches = (time/148)

The distance can also be calculated taking into account the speed of sound (=340m/s)

HC-SRO4

CODE Explanation:

· The data lines of seven-segment displays are interfaced to port-0

· Port-1, Pin-0,1 and 2 are selected lines for SSDs

· P3.0 is connected to Trig

· P3.1 is connected to the Echo pin of the sensor module

· In the main part of the Program, first Timer-1 is initialized in mode 2 (8-bit auto-reload)

When P3.0 is set high, the DELAY1 subroutine is called. After 10us P3.0 is reset to 0

· Now P3.1 is checked for a high signal. As P3.1 gets high, Timer 1 starts and every time it overflows, Register A is incremented.

· The loaded count value should be 58 (mentioned in the datasheet). So that after 58 cycles A is incremented once. But since the delay caused by instructions needs to be compensated, the count value I used was 45 (=> 255D-210D).

· The value stored in A is used to extract the measured Distance. This is done by Division instruction.

· The 8-bit data value is sent sequentially to the respective 7-segment display and is selected through the selection lines.

Distance finder based on AT89S52 and HC-SR04 ultrasonic sensors

Distance finder based on AT89S52 and HC-SR04 ultrasonic sensors

Project source code

 ###



 ORG 00H 






MOV DPTR,#SSDisplay // move LUT address to DPTR




 MOV P1,#00000000B // define P1 as output port
 MOV P0,#00000000B // define P0 as output port
 CLR P3.0 // define P3.0 as output for sending the trigger
 SET P3.1 // define P3.1 as input to receive echo 
MOV TMOD,#00100000B // define timer1 as automatic recharge timer mode 2
 MAIN: MOV TL1,#210D // load the initial value to start counting
 MOV TH1,#210D // load the recharge value
 MOV A,#00000000B // clear the accumulator
 P3.0 SET //start the clock
 CALL DELAY1 // provides 10uS width for the trigger pulse
 CLR P3.0 //end the clock
 HERE: JNB P3.1,HERE // loop here until the echo is received 
BACK: SETB TR1 //start timer1
 HERE1: JNB TF1,HERE1 // loop here until the timer runs out (i.e.; 48 counts)
 CLR TR1 //for the timer
 CLR TF1 // clear timer 1 flag
 INCA // increment A for each timer1 overflow
 JB P3.1,BACK // jump to BACK if echo is still available
 MOV R4,A // save the value of A in R4
 ACALL DLOOP //call the display loop 
MAIN SJMP // jump to MAIN loop

 DELAY1: MOV R6,#2D // 10uS delay
 LOOP1: DJNZ R6,LOOP1
 RET

 DLOOP: MOV R5,#50D // load R5 with 100D
 BACK1: MOV A, R4 //load the value in R4 to A
 MOV B,#100D // load B with 100D
 DIVAB // isolate the first digit
 SET P1.0 // activates the D1 LED display unit
 CALL DISPLAY //call the DISPLAY subroutine 
MOV P0,A // move digit unit pattern from first digit to P0
 CALL DELAY // 1mS delay
 CALL DELAY
 MOV A, B // move the rest of the 1st division to A
 MOV B,#10D // load B with 10D
 DIVAB // isolate the second digit
 CLR P1.0 //disables the D1 LED display unit
 SET P1.1 // activates the D2 LED display unit
 CALL DISPLAY 
MOV P0,A // move digit unit pattern from 2nd digit to P0
 CALL DELAY
 CALL DELAY
 MOV A, B // move the rest of the 2nd division to A
 CLR P1.1 //disables the D2 LED display unit
 SET P1.2 // activates the D3 LED display unit
 CALL DISPLAY
 MOV P0,A // move digit unit pattern from 3rd digit to P0
 CALL DELAY
 CALL DELAY
 CLR P1.2 //disables the D3 LED display unit 
DJNZ R5,BACK1 //repeat the display loop 100 times
 RET

 DELAY: MOV R7,#250D // 1mS delay
 LABEL2: DJNZ R7, LABEL2
 RET

 DISPLAY: MOVC A,@A+DPTR // get the digit unit pattern for the content in A
 RET

 SSD Display: DB 0C0H // Hexadecimal code to display DISPLAY 0
 DB 0F9H // DISPLAY 1
 DB 0A2H // DISPLAY 2
 










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Project video





 






https://www.youtube.com/watch?v=He7SEEitFP4












 



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