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-   -   Controlling PWM freq. using RDM (http://www.rdmprotocol.org/forums/showthread.php?t=1036)

lucbeullens October 14th, 2009 03:09 AM

Controlling PWM freq. using RDM

I would like to control/select the PWM frequency of a led dimmer by using RDM. I have 4 possible frequencies that I want to configure/select.

I have used 4 DMX-personalities to select 1 ,2 ,3 or 4 channels.
I could extend that and have something like this:

1 channel /250Hz
1 channel /500Hz
1 channel /1KHz
1 channel /2KHz
2 channels /250Hz
2 channels /500Hz
4 channels /2KHz

But that just don't seem to be the proper way to use DMX personalities.
Additionally I want to add a current setting as well. (100mA, 350mA, 700mA, 1A).
This would give me a list of 64 personalities

Is there a better way to implement a frequency setting or a current setting?

Using a Device Configuration Parameter would be perfect except that there are only 4 parameter defined (pan invert/tilt invert ...)

Is there anyone that has done something like this or that can advice me on this one?

Luc Beullens

kingartjr October 14th, 2009 04:59 PM

you could use personalities and sub-devices. Your root device could set the personality with the number of channels. Then have a sub-device for each channel. The personality for the channel could set the frequency of that channel. You could just add PIDS to support these configurations as well.

ericthegeek October 14th, 2009 07:47 PM

kingartjr's suggestion is a good one.

Alternately, it's perfectly valid to have 64 personalities.

mike_k October 14th, 2009 11:57 PM

If you are planning to have the device "out of the box" supported by most controllers I would suggest having 64 personalities.
Having manufacturer specific PIDs often don't blend in very well in the controller UI thus making it less intuitive to the user how to change it.

dangeross October 16th, 2009 01:07 AM

The only possible problem I see with using DMX personalities is that if in the future you add more channels, frequencies, or current settings you could easily find yourself exceeding the 8-bit limit for personalities. Unless you can get PWM_FREQ and CURRENT_LIM added to the Configuration 0x06xx PID category in the Standard manufacturer specific may be you safest bet for future product expansion.

ericthegeek October 16th, 2009 10:11 AM

I'm a little uncomfortable setting the LED current via a personality. If the wrong current setting is used, it has the potential to damage the connected LEDs. Typically, something that can damage hardware isn't the kind of setting you want to expose via a personality; It's too easy for the user to set (or mis-set).

Can you tell us a bit more about the product? Typically the max current for an LED is pre-set at the factory based on the specific LED emitters being used. If it is a factory only setting, that's a perfect application for a manufacturer specific PID.

prwatE120 October 19th, 2009 01:40 AM

I am also of the view that using the DMX_PERSONALITY for this type of operational distinction is the wrong approach. Until such time as the additional dimmer related commands are released, I would recommend the use of Manufacturer specific commands fro the functions you require. I do not think there will be many "generic" LED dimmers/controllers that provide the extent of flexibility yiou have described - and this is another reason to make use of a Manufacturer Specific PID.

Peter Willis

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