L297 L298 problem

cosimo · ‎2015-03-07

Posted on March 07, 2015 at 16:31

Hi to all, I've build the board with L297 + L298, but I've a problem..

At the power on, with enable H, full step mode, and so on, I see the reset state of the L297 with the multimeter, that is output pins are: A = 0V B = 4.4V C = 0V D = 4.4V (0101). This is ok without the stepper connected at the L298. When I connect the stepper, the L927 output pins are: A = 3.4V B = 4.4V C = 0V D = 4.4V (?101). Output A is abnormal, and vary from 3.0V to 4.2V if I turn the trimmer in the vref pin for current control..

Someone can help me? why this? L298 may be damaged?

Thanks

#l297-l298

Enrico Poli · ‎2015-04-08

Posted on April 08, 2015 at 13:23

Hi,

connecting the stepper motor to the L298 makes the A\B\C\D outputs of the L297 switching according to the PWM current control operation.

You can detect this behavior using an oscilloscope; the multimeter tries to convert the PWM signal (square-wave) in a DC value with a method depending on its circuitry.

Enrico