INDEX

L298
Stepper motor driving with ULN2003
Stepper motor diriving with L293D
Another  motor driving circuit
 

TROUBLESHOOTING L293D:
1. Insert IC into the breadboard. Make sure that IC is inserted properly into breadboard. You can verify it using continuity test in the multimeter. Test continuity between the pins of the IC and the holes  of the breadboard. If you get a beep then you can sure that IC is fitted strongly into breadboard and the portion of breadboard you are using is good.
2. Test the continuity in the 16 pins of the IC and the breadboard holes, to make sure that nothing goes wrong. You should be thorough with the steps you are taking.
3. Apply Vss=5V(Pin 16) . The first thing to apply when you connect an IC is applying Vcc and ground. Remember Vss should be in the range of 4.5V to 7V
4. Now connect ground at Pins 4, 5,12,13. Remember if you use multiple supplies, you should short circuit all grounds and this ground is applied to the Pins.
5. Now Vss and Gnd applying is over.
6. Now apply +5V to chip enable pins . Chip enable pins are pin1,9
7. Here we are trying to use both channels, at least test both channels of the IC so that we can test whether IC is good or not.
8. Apply Vc at Pin8. For testing the IC you can apply Vc=Vss=5V. When you connect the motor you should apply Vc>Vss or may it can be equal also. I have tested it.
9. The following test are done for each channels separatively. In the following explanation I refer '1' as +5V(Vss) and '0' as ground.
10.Apply Input 1 = Input 2 =0( ie,ground ) and connect multimeter to output 1 and ground of the circuit. Now test output1 and output2 voltages. Both should be zero at this condition.
11.Apply Input1=1 and Input2=0 and check voltages at output1 and output2. Remember your multimeter's one lead should be ground. Then you should get one output= Vc and other output = 0. Suppose if you got output1=Vc and output2=0.
12.Apply Input1=0 and Input2=1 and check voltages at output1 and output2. Then output1=0 and output2=Vc. That is this case is should be reverse of the previous case, motor will rotate in opposite
direction.
13.Apply Input1=1 and Input2=1 and check voltages at output1 and output2. Then output1=output2=Vc. This is the braking case. 14.Test conditions 10-13 for both channels to test the IC is good. You should test it thoroughly so that a repetition is not needed. If your IC is not working, repeat steps 1-13 to make sure IC is bad.
15.The most problems occurring are breadboard problems, IC not inserted properly, applying Vss and Vc wrongly (this can sometimes cause problems to IC), not disabling chip inhibit,absence of common ground.
16. If you are applying Vc=Vss = +5V, then you can use two LED's to see outputs.
17.When chip inhibit is enabled, ie chip is not working the outputs will be high impedance, you can test high impedance using an LED. First connect the cathode of LED to ground through a series resistor of 330ohm and test the output. LED will not glow. The apply 5V to the anode of the LED and apply output to the cathode through a series resistor of 330 ohm. Now also LED won't glow. Now you can assure that the output is high impedance.
18.Before connecting motor to the outputs of L293D, first test the motor is working with the desired VC by applying VC and ground directly to the two leads of the motor. Confirm this first, then  connect the motor.
19.L293d has a thermal shutdown function. So see it is working in all conditions of the circuit and robot
Links:
http://www.me.umn.edu/education/courses/me2011/robot/technotes/ L293/L293.html