noises in pulse sn754410 driver

Discussion in 'General Electronics Chat' started by omerysmi, Mar 27, 2016.

  1. omerysmi

    Thread Starter Member

    Oct 10, 2014
    44
    0
    Hi, i use the ic sn754410 to operate step motor, everything work well but when i measure the output pulses (Y4,Y3,Y2,Y1) in oscilloscope there are a lot of noises in the pulse.

    example:

    [​IMG]

    Does there is some way to remove all of these noises? maybe with capacitors? or maybe the problem is on the oscilloscope/probe?

    The datasheet of the sn754410:
    http://www.ti.com/lit/ds/symlink/sn754410.pdf
     
    Last edited: Mar 27, 2016
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,653
    632
    It might be that the noise originates in as other channels switch. From the image it appears that some of the noise is there because of a voltage drop in the ground between wherever your probe is grounded and the ground pin on the SN754410.

    There is also the possibility of the input having some of these glitches on it.

    You can fix the glitches with capacitors but if the pulse frequency is high enough there is a chance that the constant switching across the capacitor could destroy the driver or the capacitor, so it is best to not have the glitch in the first place.

    Some things to check:
    Reposition the scope ground

    Check for clean signal on input

    Check Vcc pin and see if it is not jumping around enough to cause problems with the internal logic

    If you post a schematic it might help you obtain a more accurate diagnosis.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,290
    1,255
    I think what you may be seeing is the back emf of the motor and the switching of the other phases. If so nothing to worry about. As Dick says a schematic and where the scope probe and ground are would maybe clear it up.
     
  4. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    Do you have the recommended 0.1uF on pin 16 and 1uF on pin 8 of the 754410?
     
  5. omerysmi

    Thread Starter Member

    Oct 10, 2014
    44
    0
    No..it could fix the spikes?

    This is my circuit:

    [​IMG]
     
  6. DickCappels

    Moderator

    Aug 21, 2008
    2,653
    632
    The bypass capacitor certainly could help. Did you check the power supply pin and the signal inputs to see if they are clean, or somewhat clean?
     
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