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Raspberry Pi Forum RaspberryPi2  and 120VAC "PWM" capabilty question
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  • pwm_controller
  • 120vac
  • triacs
  • pwm
  • raspberry-pi
  • christmas_lights
  • lightshowpi
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RaspberryPi2  and 120VAC "PWM" capabilty question

Former Member
Former Member over 10 years ago

Hello all,

 

I am in the military and aspiring to be  an electrical engineer (Hope to start school this October at Arizona State). Anyhow...

 

I was tasked to build a christmas tree light show this year by the "Big Wigs" of the base. So I jumped into research and found the RaspberryPi to be capable of doing some of the features I would need.

 

1. I found an example of a library called LightshowPi which essentially uses a python script to play a midi and mp3 file at the same time. I could then use the midi to control other GPIOs to turn on and off lights and certain moments of each song in playlist.

 

2. PWM! So if this was a perfect world the lights provided to me would be powered by DC. However, I am told they are powered with 120VAC. I have yet to see the lights in person, so I can't be certain. Although I do know they are RGB LEDs. I did see the lights last year driving by and the tree periodically changes color (telling me there is some form of PWM happening here).

 

So, if the light strands are indeed 120VAC; I need to figure out how a "PWM" on 120VAC is accomplished. Essentially, what I need to do is be able to use a Raspberry PI to play music and send signals to each strand of light of this tree. If it were DC this would be easy as I have found chips that could add several GPIOs and handle PWM as needed.

 

I have read about TRIACS and it smells like a possible solution but Im not certain how (if at all) a DC signal could "PWM" a TRIAC.

 

I would enjoy some feedback and possible solutions.

 

Cheers,

 

Clayton Allen

 

Message was edited by: Clayton Allen Punctuation Error Spotted

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  • clem57
    clem57 over 10 years ago

    Firstly, just because they plug into 120 VAC, does not mean that the string is same. It may have a transformer to 12 VDC!

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  • clem57
    clem57 over 10 years ago

    Firstly, just because they plug into 120 VAC, does not mean that the string is same. It may have a transformer to 12 VDC!

    C

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