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RC4 Knowledge Base

Set PWM Frequency to Eliminate Video Artifacts

I. Banding, beating, and other visual artifacts can be an issue when working with video.  Increasing the PWM frequency resolves this:

A. Press and hold the Set B ButtonSet B ButtonAll RC4 dimmers have Set buttons for each individual dimmer output. The second button is the Set B button. On a 2-channel device these are Set A and Set B buttons. A 4-channel device adds Set C and Set D. The most common use of the Set button is to assign a DMX channel and […]
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1. It will flash a pattern on DimA and DimB outputs to indicate that a PWM frequencyPWM frequencyPWM stands for Pulse-Width Modulation.  It is a method for using a switching device (one that can only be on or off) to create what appears to be analog changes in level.  This is done by switching on and off at a high speed and varying the proportion of the time for each.  For example, of the […]
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increment has been made

2. It will automatically move to the next available frequency

3. The flashing pattern is different for each available frequency, indicating which frequency has been selected.

B. The default PWM frequency is different for different system families:

1. RC4Magic and RC4Magic-900 dimmers default to 615Hz, ideal for human eyes in a live performance environment

2. LumenDim and W-DIM dimmers default to 5kHz, ideal for video capture at normal frame rates

II. In this example, both dimmers start at the default setting of 615Hz.

III. Each long-press of the Set B button increments to the next PWM frequency:

  1. 615Hz (default)
  2. 1.2kHz
  3. 5kHz
  4. 10kHz
  5. 20kHz
  6. 40kHz
  7. The next long-press cycles back to #1 (615Hz)

IV. The correct PWM frequency will eliminate visible artifacts:

A. The flashing pattern on DimA/DimB is different for each available frequency, indicating which frequency has been selected.

B.  A chart of PWM frequencies clarifies all of this.

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