Changing PWM Frequencies for Video Applications (LumenDimM4)

I. Changing the PWM frequency on the LumenDimM4

A. The unit must be receiving streaming data from the transmitter in this process

1. The yellow LED on the LumenDimM4 will be illuminated when it is receiving streaming data

2. Without streaming data, the unit is in bump button mode and will not be able to set functions

B. Multiple PWM frequencies work only for the ISL curves which are used for LEDs

1. PWM frequencies are only significant when working with LEDs

2. When doing video, if banding and beating is present in your shots, the PWM frequency needs to be increased

II. Changing the PWM frequencies on a LumenDimM4 that is restored to default mode (DMX channels 1 to 4) with an ISL slow curve dimmer curve

A. To see the blink pattern on the LumenDImM4 clearly, it is recommended that the DMX channel remains down during this process.

1. This is because the dimmers are used as indicators

B. The default frequency of the LumenDimM4 is 5 kHz

C. Using a small tool like a bent paper clip, press and hold the Set B Button for three seconds to move up to the next incremental frequency

D. The Set A  button  and Set B button  will blink a pattern

1. This  blink patternindicates the newly selected PWM frequency

2. Written ocumentation provides a blink pattern frequency chart for reference

E. The frequency has now changed to 10kHz

F. The PWM frequency can be made faster using the same process

G. The PWM frequency essentially doubles each time it is adjusted up

H. Currently, the highest PWM frequency offered on the LumenDimM4 is 40kHz

I. Adjusting the PWM frequency once again after it is set at 40kHz will take it down to the lowest frequency, 615 Hz

J. The PWM frequency is remembered

1. When the unit is turned off and then powered back on, the new PWM frequency will remain

2. When restoring defaults, the PWM frequency will return to the original setting of almost 5kHz

Why bother with PWM frequencies — why not just set it to 40kHz?  There are two reasons:

A. Lower frequencies deliver higher resolution, which improves the smoothness of dimming at the bottom end of the curve (very low dim levels)

B. Lower frequencies are more electrically efficient and can deliver more current with less heat than higher frequencies

C. The lowest ISL frequency of 615Hz looks best to the human eye in live entertainment applications

C. Higher frequencies eliminate artifacts in motion-picture capture.  Use the lowest frequency that does the job, usually 5kHz.  Do test shots whenever possible to find the ideal frequency.  LumenDim devices default to 5kHz, optimal for most motion-picture applications

D. The faster the video frame rate, the higher the PWM frequency needs to be.  For very-slow-motion capture (very high frame rate) 40kHz may be required.  Remember that this reduces dimmer resolution and may look a little bit more “steppy” when dimming at low levels, and the dimmer will generate more heat when driving large loads.

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