Control/Dimming Dimming a Power Inverter

soundofsparks

Active Member
I have a question that I believe I know the answer to, but thought I would crowd source it in case I'm wrong.

I have a prop that wants to move around the stage and be covered in Christmas Lights. I had looked at using LED 12VDC Christmas Lights on an RC4 Magic and 12VDC battery so that I can at least turn them on and off.

I had hoped that I could find some dimmable 12VDC LED Christmas Lights, but it doesn't seem like that's a thing (please interject here if you have some links or thoughts).

So, my backup plan is to use the RC4 Magic as a switch for the 12VDC LED Christmas Lights...

BUT then I wondered if I could use a power inverter and 120VAC Incandescent Christmas Lights. To make that work easily, I would have to go Battery > RC4 > Power Inverter > Christmas Lights. Essentially, dimming the input voltage going into the power inverter.

My question is, if I changed the input to the power inverter like this would I see dimming on the output side? Or would the power inverter just not work properly. My thought is that the power inverter would just not work properly, but I'm not sure why that would be true because it seems like it should work.

So what do you think? Is that an insane idea?
 
I’m surpised you’re unable to dim them. What happens when you try? They probably do not dim with varying voltage, but they should dim perfectly with the PWM output of our RC4 dimmers.

For 120V LED strings, each LED introduces a voltage drop. Usually, you can cut the string to 1 tenth the length and you will have the appropriate drop for a 12V supply. Another factor, however, is that LEDs only light in one power polarity, and AC is alternating. Thus, they are only lighting for half the time and you’ll see a slight flicker. This is more visible peripherally, as when you quickly move your head. When you power from a DC supply, it is one polarity: connected one way the LEDs do not light at all, and connected the other way they light continuously with no flicker. This is also running them harder because they don’t get the break 60 times a second that ac power provides, and they will look brighter. To avoid accidentally damaging them, you might want to start with 1/20th of the original string and go down from there.

Another way is to use dimming and set a limit at 50% (or a bit lower of you do the sinewave math). That way your maximum duty-cycle to the LEDs ends up the same as with AC power.

Once you find the ideal length for 12V operation, you can join the starts of many short strings together in parallel and run them all from the same battery. In the end, you have all the same LEDs, zero flicker (because we PWM much faster than 60 Hz), and it should be fully dimmable with an RC4 dimmer.

For additional help, open a support ticket at [email protected]. I’m here along with others to help.

Jim
RC4
 
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P.S. An inverter is conceptually workable, but definitely eliminates dimming capability and is a very inefficient solution. I would never go that way... it’s big, unruly, and unnecessary. :)
 
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Jim -- This is all great!

Aside from the RC4s and the batteries, I don't actually own any of the other things so I was asking before buying as it were. So it seems that I should go with 12 VDC LED Christmas Lights and should be good to go.

Thanks so much!
 

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