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Dmx512 -> pwm???

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ym2k

New Member
Hi, I had been programming pic these few days but fails to get what i want. I decided to use pic to decode dmx512 signals and translate them to pwm signals for lightnings. I alreadly found my way to decode the signal with constant monitor on the dmx512 signal. But i cannot think of any way to convert the data to 3 channel pwm in 256 levels. I try to call a function to decode the signal and then another signal to generate pwm, but the time to decode the signal is too long and create a huge delay in my pwm. Any idea to use pic or/with other components to get what i want?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
ym2k said:
Hi, I had been programming pic these few days but fails to get what i want. I decided to use pic to decode dmx512 signals and translate them to pwm signals for lightnings. I alreadly found my way to decode the signal with constant monitor on the dmx512 signal. But i cannot think of any way to convert the data to 3 channel pwm in 256 levels. I try to call a function to decode the signal and then another signal to generate pwm, but the time to decode the signal is too long and create a huge delay in my pwm. Any idea to use pic or/with other components to get what i want?
What sort of lighting are you trying to control?. PWM is usually used for low voltage DC control, not AC mains control - you use phase control for that. I've seen various designs on the net for DMX using PIC's, I suspect a google search will probably find something suitable?.
 

crust

Member
Are you trying to make the equivalent of a DMX dimmer pack? As Nigel mentioned the normal method is to use phase control. Or are you trying to make a PWM output and then LP filter it to drive an analog dimmer?
 

ym2k

New Member
I am going to use the pwm signal to drive my mosfet so i can use the switching mosfet to drive my dc lightnings. I need to convert to 3 pwm signals to control their brightness, i made several search and return me nothing. I had been working on this for quite some time....
 

Oznog

Active Member
Why are you not using the hardware PWM?
Most PICs only have 2 channels, but some have more.
You can also get any number of DAC chips which do 8 bit PWM.

Now if you're doing PWM in software, the best thing to do is deal with it on an interrupt basis. PWM freq has to be fairly low to avoid having too many interrupts, but probably sufficient for lighting.

What types of DC lights are these? LEDs are aesthetically unpleasing with lower freq of PWM.
 
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