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Motor noise on video image — Parallax Forums

Motor noise on video image

ArchiverArchiver Posts: 46,084
edited 2001-05-30 23:44 in General Discussion
Greetings all,

I have a BSII on a board controlling two L293D circuits, which are
connected to four small pumps. In addition the BSII turns a small video
camera on and off as well. The board is powered by two 7.1 volt nicad
batteries, one battery powering the BSII and the two together powering
the motors and camera. When the motors are on they induce noise into the
video image. Who has suggestions for filtering out the noise from the
motors.

Regards, Theron Wierenga

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2001-05-30 18:00
    The most effective filtering for conventional DC motors is usually series
    chokes in both leads (or a common mode choke) and a capacitor across the
    motor. The power supply should also be heavily bypassed. Often the motor
    housing must be grounded as well, to suppress radiated noise...

    > I have a BSII on a board controlling two L293D circuits, which are
    >connected to four small pumps. In addition the BSII turns a small video
    >camera on and off as well. The board is powered by two 7.1 volt nicad
    >batteries, one battery powering the BSII and the two together powering
    >the motors and camera. When the motors are on they induce noise into the
    >video image. Who has suggestions for filtering out the noise from the
    >motors.

    Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
    Manufacturer of the famous BOB-II Serial Video Text Display Module!
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-30 18:25
    Mike,

    Series chokes in the leads to the motors I assume, not the video card?
    What size for a small 12 v. DC motor
    drawing 250 ma?

    Thanks, Theron

    Mike Hardwick wrote:

    > The most effective filtering for conventional DC motors is usually series
    > chokes in both leads (or a common mode choke) and a capacitor across the
    > motor. The power supply should also be heavily bypassed. Often the motor
    > housing must be grounded as well, to suppress radiated noise...
    >
    > > I have a BSII on a board controlling two L293D circuits, which are
    > >connected to four small pumps. In addition the BSII turns a small video
    > >camera on and off as well. The board is powered by two 7.1 volt nicad
    > >batteries, one battery powering the BSII and the two together powering
    > >the motors and camera. When the motors are on they induce noise into the
    > >video image. Who has suggestions for filtering out the noise from the
    > >motors.
    >
    > Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
    > Manufacturer of the famous BOB-II Serial Video Text Display Module!
    >
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  • ArchiverArchiver Posts: 46,084
    edited 2001-05-30 20:20
    When I was messing alot with vehicle-mounted radio stuff, we had alot of
    noise problems from the blower motor, wipers and electric radiator fan. Our
    fix was to wind some filters using the ferrite cores from Radio Shack. They
    have various schemes for winding the wire depending on what you want to do.
    Original Message


    > The most effective filtering for conventional DC motors is usually series
    > chokes in both leads (or a common mode choke) and a capacitor across the
    > motor. The power supply should also be heavily bypassed. Often the motor
    > housing must be grounded as well, to suppress radiated noise...
    >
    > > I have a BSII on a board controlling two L293D circuits, which are
    > >connected to four small pumps. In addition the BSII turns a small video
    > >camera on and off as well. The board is powered by two 7.1 volt nicad
    > >batteries, one battery powering the BSII and the two together powering
    > >the motors and camera. When the motors are on they induce noise into the
    > >video image. Who has suggestions for filtering out the noise from the
    > >motors.
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-30 23:44
    It's been too long since I did anything like this, but you definitely want
    the chokes and bypass cap as close to the motor terminals as possible.
    Inductance isn't teribly critical. Use wire just big enough for motor stall
    current, and wind as much as you can in a single layer on small cores. If
    you use toroids, watch out for core saturation! Common mode choke windings
    would be best in this case. That's where you wind a bifilar pair of wires
    on a single core and connect them so motor current flows in opposite
    directions, cancelling magnetic flux in the core. If you purchase chokes,
    something in the 10~100uH range should be appropriate.

    > Series chokes in the leads to the motors I assume, not the video
    card? What size for a small 12 v. DC motor
    >drawing 250 ma?

    Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
    Manufacturer of the famous BOB-II Serial Video Text Display Module!
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