basic questions about PWM's

Discussion in 'The Projects Forum' started by kendoo, Dec 21, 2010.

  1. kendoo

    Thread Starter New Member

    Dec 21, 2010
    Hi All,
    i have bought a PWM board through ebay to control the rpm of my 12v salt spreader motor. It works really well especially at 1/10th the price of a dealer item. The board i bought is small, rated at 24amps, has a 10k linear pot. When i turn the pot the RPM of the motor increases or decreases. Perfect. I am wiring up another truck with the same application. In doing some reasech on another PWM board, i've noticed some of the PWM include a second pot to adjust the frequecncy. That's where i'm lost for info. Do i need (or want) to adjust the frequency, and how does that relate to my spinner motor? I'm guessing my current PWM is hard set at something like 100hz?

    Here's my guess: P1 adjust the length of the pulse
    P2 adjust how many pulse per sec? How will this affect the performance of my motor?

    Also as an aside; do they make a PWM board with one input voltage and have 2 seperate PWM outputs? (50a total)

    Many Thanks in advance!!!
    Merry Christmas
  2. bassplayer142

    Active Member

    Jan 2, 2007
    If you change the frequency of a pwm signal you do not change the average power or voltage delivered to the motor driver. Therefore, changing the frequency does not change the speed of the motor. This is assuming that the pwm frequency is in a normal range needed for the motor.

    If you have ever heard the a whining motor it is most likely due to the pwm switching frequency. Here is a link that should help.