View Full Version : Help controlling DC motor with L298

04-28-2005, 11:22 PM
Hi roboticists,
I am trying to interface a 12v/1A DC motor to PIC through L298 dual H bridge IC. Can anybody please suggest the high speed diodes that i should connect in bridge configuration around motor inputs.
I gave 5v to logic supply, input1 and enable A pin. 12v to supply voltage pin, and 0v to input 2. i got 12v at output1 pin and 4v instead of 0v at output2. when i connected motor without diode bridge to output1 and 2, the output at both output1 and 2 was 12v and output across motor was zero. Can anybody please explain why this happened and guide me.
Diodes are used for conductiong back emf voltage, right? Why the motor does not rotate when diode bridge is not used?
Thanks in advance.


04-30-2005, 11:23 PM
I was able to run the motor after i connected the diode (1N5819) bridge across the motor terminals. But i still have not figured out how it works. Can anybody pleas give explanations regarding how diode bridge helps in running the motor apart from conducting the back emf of the motor.


05-03-2005, 11:52 AM
We can better figure out your problem, if you can show us your schematic.

05-05-2005, 12:33 PM
these fly back diodes (as they are also known) act as a path to dessipate the stored magnetic energy in the motor coils, when its switched off ... thus protecting the driving circuit from high voltage surges...

12-24-2005, 02:22 AM
free wheeling diodes r just to protect ur switches from the motors back emf