L293D Dual H-Bridge Motor Driver

L293D is a dual H-Bridge motor driver, So with one IC we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction and if you have motor with fix direction of motion the you can make use of all the four I/Os to connect up to four DC motors. L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF ouput diodes are included within the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a best choice for DC motor driver.

A simple schematic for interfacing a DC motor using L293D is shown side.

As you can see in the circuit, three pins are needed for interfacing a DC motor (A, B, Enable). If you want the o/p to be enabled completely then you can connect Enable to VCC and only 2 pins needed from controller to make the motor work.


As per the truth mentioned in the image above its fairly simple to program the microcontroller. Its also clear from the truth table of BJT circuit and L293D the programming will be same for both of them, just keeping in mind the allowed combinations of A and B. We will discuss about programming in C as well as assembly for running motor with the help of a microcontroller.

Displaying data ADC 0804 in 8x7 Segmen as a Decimal

In this lesson will be learn how to display data ADC on 8 x 7 segmen, for a simple task, we assume ADC have input ranges 0 - 5 volt, and then will display data as desimal that must be 3 digit 0 - 255, and each digit would be placed on 3rd, 2nd and 1st 7 segmen.

Figure 2.5.2. Connecting ADC and display to 7 segmen

Step 1st
Build the circuit as shown in figure 2.5.2. As you seen on figure 2.5.2. P3.0 trough P3.7 is connected to DB0 - DB7 ADC0804, and P2.0- P2.7. is connected to transistor driver, and P3.0 trough P3.7. is connected to 7 Segmen. Remember, that all we want to do with this lesson is write data ADC, to 8 x 7 Segmen.

Step 2nd
In this step, you must tipe the assembly program to make your 8 x 7 Segmen shown the data, we assume that you have already known the editor, we used RIDE-51 to edit the program. ( Download File asm : exp252.zip)

      org 0h
hundreds equ 30h
tens   equ 31h
ones     equ 32h
start: call ADC
     call Bin2Dec
     call Display2SevenSegmen
     sjmp start
;
;=================================================
;this subroutine is used to take data from ADC and
;keep to Accumulator
;=================================================
ADC:   mov A,P0
     nop
     nop
     ret
;
;========================================================
;this subroutine is used to convert binary data from ADC
;become decimal 3 digit
;========================================================
Bin2Dec:
     mov b,#100d
     div ab
     mov hundreds,a
     mov a,b
     mov b,#10d
     div ab
     mov tens,a
     mov ones,b
     ret     
;===============================================
;this subroutine is used to convert data ADC to
;8 x 7 segmen
;===============================================
Display2SevenSegmen:
     Mov P2,#11111111b
     mov A, Hundreds
     mov DPTR,#Data7segmen
     movc A,@A+DPTR
     mov P0,A
     clr P2.5
     call delay
;
     mov A,tens
     mov DPTR,#Data7segmen
     movc A,@A+DPTR
     setb P1.5
     mov P0,A
     clr P2.6
     call delay
;
     mov A,ones
     mov DPTR,#Data7segmen
     movc A,@A+DPTR
     setb P1.6
     mov P0,A
     clr P2.7
     call delay
     ret
;
delay: mov R0,#0
delay1:mov R2,#0fh
     djnz R2,$
     djnz R0,delay1
     ret
;
Data7segmen:
    db 11000000b,11111001b,10100100b,10110000b,10011001b
    db 10010010b,10000010b,11111000b,10000000b,10010000b
end

Step 3rd
Safe your assembly program above, and name it with adc2.asm (for example) Compile the program that you have been save by using RIDE-51, see the software instruction.

Step 4th
Download your hex file into the microcontroller by using Microcontroller Laros ATMEL ISP software, see the instruction.After download this hex file you'll see the action of ADC ( of course if your cable connection and your program are corrected )

Display Keypad 4 x 4 with 8x7 Seven Segmen

Continuing your sucsess, will try your knowledge with more complex experiment by read out the keypad 4 x 4 data with 8x7 Seven Segmen.
Figure 2.8.4.Keypad Connection to Microcontroller with 8x7 segmen

Step 1st
Build the circuit as shown in figure 2.8.4. As you seen on figure 2.8.4 P3.0 trough P3.7 is connected to keypad 4 x 4 and 8 x 7 Segmen to read keypad data, connected to P0.0 trough P0.7., P2.0 and P2.1 connected to RS and EN each.

Step 2nd
In this step, you must tipe the assembly program to scan your keypad data, we assume that you have already known the editor, we used RIDE-51 to edit the program. ( Download File asm : exp283.zip )

;the following experiment is used to scan
;keypad 4x4 and result of scan will be released
;to Display 7 Segmen
row1 bit P3.4
row2 bit P3.5
row3 bit P3.6
row4 bit P3.7
col1 bit P3.0
col2 bit P3.1
col3 bit P3.2
col4 bit P3.3
;
keydata   equ 70h
keybounc  equ 71h
keyport   equ P2
     org 0h
start: call keypad4x4    ;calling subrutine keypad4x4
     Mov A,keydata     ;A = keydata
     Cjne A,#0FFh,Wr7Seg;
     sjmp start        ;LOOPING FOREVER PART 1
;
Wr7Seg:
;================================================
;I left the assembly instruction for you to learn
;=================================================
;
delay: mov R0,#0
delay1:mov R2,#50
     djnz R2,$
     djnz R0,delay1
     ret
;
;====================================
; subroutine scan keypad 4x4
;====================================
Keypad4x4:
     mov keybounc,#50    ;keybounc = 50        
     mov keyport,#0FFh   ;keyport=P2= FF
     clr col1            ;col1= P3.0 = 0
Detect:jb row1,key1        ;jump to Key1 if row=1
     djnz keybounc,Detect
     mov keydata,#00h    ;Keydata =00h
     ret
;
key1: jb row2,key2         ;jump to key2 if row2=1
    djnz keybounc,key1
    mov keydata,#04h     ;Keydata = 04h
    ret
;
key2: jb row3,key3         ; idem
    djnz keybounc,key2
    mov keydata,#08h
    ret
;
key3: jb row4,key4         ; idem
    djnz keybounc,key3
    mov keydata,#0Ch
    ret
;
key4: setb col1
    clr col2
    jb row1,key5
    djnz keybounc,key4
    mov keydata,#01h
    ret
;
key5: jb row2,key6
    djnz keybounc,key5
    mov keydata,#05h
    ret
;
key6: jb row3,key7
    djnz keybounc,key6
    mov keydata,#09h
    ret
;
key7: jb row4,key8
    djnz keybounc,key7
    mov keydata,#0Dh
    ret
;
key8: setb col2
    clr col3
    jb row1,key9
    djnz keybounc,key8
    mov keydata,#02h
    ret
;
key9: jb row2,keyA
    djnz keybounc,key9
    mov keydata,#06h
    ret
;
keyA: jb row3,keyB
    djnz keybounc,keyA
    mov keydata,#0Ah
    ret
;
keyB: jb row4,keyC
    djnz keybounc,keyB
    mov keydata,#0Eh
    ret
;
keyC: setb col3
    clr col4
    jb row1,keyD
    djnz keybounc,keyC
    mov keydata,#03h
    ret
;
keyD: jb row2,keyE
    djnz keybounc,keyD
    mov keydata,#07h
    ret
;
keyE: jb row3,keyF
    djnz keybounc,keyE
    mov keydata,#0Bh
    ret
;
keyF: jb row4,Nokey
    djnz keybounc,keyF
    mov keydata,#0Fh
    ret
Nokey:mov keydata,#0FFh  
    ret
;================================
;The end of Keypad 4x4 subroutine
;================================
end

Step 3rd
Safe your assembly program above, and name it with key3.asm (for example) Compile the program that you have been save by using MIDE-51, see the software instruction.

Step 4th
Download your hex file ( key3.hex ) into the microcontroller by using Microcontroller Laros ATMEL ISP software, see the instruction.After download this hex file you'll see the action of Keypad 4 x 4 ( of course if your cable connection and your program are corrected )

Displaying data ADC 0804 in 8x7 Segmen as a Decimal

In this lesson will be learn how to display data ADC on 8 x 7 segmen, for a simple task, we assume ADC have input ranges 0 - 5 volt, and then will display data as desimal that must be 3 digit 0 - 255, and each digit would be placed on 3rd, 2nd and 1st 7 segmen.

Figure 2.5.2. Connecting ADC and display to 7 segmen

Step 1st
Build the circuit as shown in figure 2.5.2. As you seen on figure 2.5.2. P3.0 trough P3.7 is connected to DB0 - DB7 ADC0804, and P2.0- P2.7. is connected to transistor driver, and P3.0 trough P3.7. is connected to 7 Segmen. Remember, that all we want to do with this lesson is write data ADC, to 8 x 7 Segmen.

Step 2nd
In this step, you must tipe the assembly program to make your 8 x 7 Segmen shown the data, we assume that you have already known the editor, we used RIDE-51 to edit the program. ( Download File asm : exp252.zip)

org 0h
hundreds equ 30h
tens equ 31h
ones equ 32h
start: call ADC
call Bin2Dec
call Display2SevenSegmen
sjmp start
;
;=================================================
;this subroutine is used to take data from ADC and
;keep to Accumulator
;=================================================
ADC: mov A,P0
nop
nop
ret
;
;========================================================
;this subroutine is used to convert binary data from ADC
;become decimal 3 digit
;========================================================
Bin2Dec:
mov b,#100d
div ab
mov hundreds,a
mov a,b
mov b,#10d
div ab
mov tens,a
mov ones,b
ret
;===============================================
;this subroutine is used to convert data ADC to
;8 x 7 segmen
;===============================================
Display2SevenSegmen:
Mov P2,#11111111b
mov A, Hundreds
mov DPTR,#Data7segmen
movc A,@A+DPTR
mov P0,A
clr P2.5
call delay
;
mov A,tens
mov DPTR,#Data7segmen
movc A,@A+DPTR
setb P1.5
mov P0,A
clr P2.6
call delay
;
mov A,ones
mov DPTR,#Data7segmen
movc A,@A+DPTR
setb P1.6
mov P0,A
clr P2.7
call delay
ret
;
delay: mov R0,#0
delay1:mov R2,#0fh
djnz R2,$
djnz R0,delay1
ret
;
Data7segmen:
db 11000000b,11111001b,10100100b,10110000b,10011001b
db 10010010b,10000010b,11111000b,10000000b,10010000b
end

Step 3rd
Safe your assembly program above, and name it with adc2.asm (for example) Compile the program that you have been save by using RIDE-51, see the software instruction.

Step 4th
Download your hex file into the microcontroller by using Microcontroller Laros ATMEL ISP software, see the instruction.After download this hex file you'll see the action of ADC ( of course if your cable connection and your program are corrected )