Help with Diode Selection

Discussion in 'The Projects Forum' started by emblematic, Feb 25, 2011.

  1. emblematic

    Thread Starter New Member

    Feb 21, 2011
    I need help selecting a suitable diode for a custom application, I am at my wits end trying to figure this out and have read lots online but can't make sense of it, any help would be appreciated.

    I have four power wires (green & purple, red & gray) that need to power a motor & actuator with respect to the following:

    Green and Purple must always ONLY power blue and black wires on device.

    Red and Gray must always power ALL wires on device (blue, black, white and brown).

    The operating voltage is 12VDC to 14.5VDC with a draw of no more than 1A. I believe I need two links with diodes. What kind of diode should I be looking for and what are the specifics of the values (forward current, reverse, etc.) that I should pay attention to?

    This image should help explain my problem:


    Thanks in advance
    BTW FWIW, the project is using a power window motor which only has one motor for L/R panning and an actuator that must be powered in addition to the motor for U/D functions. I am wiring up the single motor and actuator unit to a car which previously had a dual discrete motors for L/R and U/D functions.
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    This circuit would only work provided that all four wires are positive, with a common negative return. [​IMG]This is not shown.

    Please re-post your diagram showing the polarity of the connections, including any common connection.
  3. hobbyist

    Distinguished Member

    Aug 10, 2008
    Logically it looks like it would work.

    However, depending on the signal source to the power wires, if they are some sort of electronic device powering the power wires, then the diodes will provide a path from one set of power wires back to the other set of power wires,.back to the original signal source.

    The only solution to solve that would be to drive the blue and black wires inputs with a diode as well.
    And make sure the blue and black wires have there diodes cathodes connected directly to the white and brown wire original diodes cathodes.
    Too keep the power wires isolated at that point, so that the signal sources are isololated from eachother.

    Possibly the device being driven may have a path of ground signal from the blue and black wires thru the diodes and back to the device other inputs.

    If that's the case you would need steering diodes connected anod to anode on the white and brown wires to the original diodes anodes already connected to the brown and white wires.

    That way it ensures that all the signals are steered in proper directions, without interfering with other parts of the circuits.
    Last edited: Feb 26, 2011
  4. emblematic

    Thread Starter New Member

    Feb 21, 2011
    Thanks so much for your responses, guys.

    The motor and actuator operate under normal and reversed polarity depending on which direction you want to drive the motor.

    I've attached below the wiring and directionality for the source wires and device wires and also another image with more information.

    Single Motor Wiring:

    Drives a single motor, which pans right/left:
    PAN RIGHT: Black Negative, Blue Positive
    PAN LEFT: Black Positive, Blue Negative

    Drives an actuator, which redirects torque from motor to up/down, to accomplish up/down movement, motor must also be driven (all four wires powered). The white & brown actuator wires will power the actuator in normal or reverse polarity.

    PAN UP: Black & White Positive, Blue & Brown Negative
    PAN DOWN: black & white Negative, Blue & Brown Positive

    Double-Motor Source Leads:

    Wires designed to run motor with independent l/r and u/d motors (2 motors):

    PAN RIGHT: Green Negative, Purple Positive
    PAN LEFT: Green Positive, Purple Negative
    PAN UP: Red Negative, Grey Positive
    PAN DOWN: Grey Negative, Red Positive


    Original Dual Motor:

    Single Motor replacement:
  5. emblematic

    Thread Starter New Member

    Feb 21, 2011
    I'm having a hard time deciphering which diode would work best from the following options:

    I'm looking at the 1A max HVCA diodes and there seem to be many subtle differences:

    One HVCA unit (this one) is advertised as "DIODE; 1 A (MAX.) @ 25C IF; 1.1 V (MAX.) @ 25C; 5 UADC (MAX.) @ 25C IR"

    What does 1.1V (MAX) mean? Is that the maximum drop in voltage from the original current presents? Or does that mean that it only supports voltages below 1.1V? I'll be running 14.4VDC max.

    I've also modified my drawing to include your suggestions, please advise as appropriate:

    Thanks in advance.
  6. emblematic

    Thread Starter New Member

    Feb 21, 2011
    Updated image showing corrected colors. I've got some unidirectional diodes which I'll be attempting this circuit with and I'll let you know if it works!