Issue with command pump

Discussion in 'General Electronics Chat' started by Fab6657, Nov 11, 2010.

  1. Fab6657

    Thread Starter New Member

    Jan 9, 2009
    5
    0
    Hello all's,

    first sorry for the not so good english, this is not my mother langage.

    I like to ask you help, i developping a command pump circuitry with microchip pic. This is a pwm command to slow down-up the speed of the pump and also reverse the fill-up and fill-down the fuel.

    My problem is that sometime the relay is not activated when i reverse the rotation of the pump. I don't no if the relay is 'glued on' while current is passing, or if this is an effect of the dc-motor. The result is that the pump always run in the same direction. If no motor is attached, the reverse seams to run well !

    I attach the part of the schema that are in use. If you have some idea, thanks' for help.

    Fabrice
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    Your circuit looks OK. Do not reverse the motor without stopping it first or the relay contacts might weld.

    Make sure the power supply to the PIC is well filtered. Noise from the motor might affect the PIC.
     
  3. Fab6657

    Thread Starter New Member

    Jan 9, 2009
    5
    0
    Hello,

    yes i think also that the motor stop not enough.
    The pic have a 100nF for decoupling the noise.

    I will changing the code with a pause between
    the rotation and try !

    Thank's

    Fabrice
     
  4. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    You may also want to find a different location for your relay coil source.
     
  5. Fab6657

    Thread Starter New Member

    Jan 9, 2009
    5
    0
    Hello

    what do you mean with different location ?
     
  6. Fab6657

    Thread Starter New Member

    Jan 9, 2009
    5
    0
    Hello,

    i complete underestimated the back electromagnetical flux from the dc motor. So i put a 1N4148 Diode in the circuit , and no problem anymore !

    Fabrice
     
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