# dimming LED strip lights



## icedawg (Oct 15, 2018)

I have some LED strips controlled by a Caseta dimmer. My problem is I need the lights to go even dimmer than the dimmer switch will allow. I've already adjusted the low end trim on the dimmer switch to the lowest level but it's still not dim enough. The tricky part is, I don't want to also reduce the light output at the brightest level of the strips.

Any ideas?


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## MeMeMe (Oct 16, 2018)

Without knowing what you have controlling/driving the strips (or are they AC strips), there is little help that can be offered.


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## DIWdiver (Oct 16, 2018)

I just googled "caseta". It's a Lutron product, a 120V line-frequency dimmer compatible with incandescent and other dimmable 120V lights.

The only thing I can think of is to add some diodes in series with one of the lines from the dimmer to the lights. Dropping a few volts might make a big difference at the low end and only a very small difference at the high end. It depends on how low "LOW" is already.


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## MeMeMe (Oct 16, 2018)

DIWdiver said:


> I just googled "caseta". It's a Lutron product, a 120V line-frequency dimmer compatible with incandescent and other dimmable 120V lights.
> 
> The only thing I can think of is to add some diodes in series with one of the lines from the dimmer to the lights. Dropping a few volts might make a big difference at the low end and only a very small difference at the high end. It depends on how low "LOW" is already.



Most LED drivers would detect phase angle, not voltage so this is unlikely help unless it's AC voltage LED strip.


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## DIWdiver (Oct 18, 2018)

Of course it's an AC voltage strip. If it weren't, the Caseta wouldn't work with it.

LED strips don't have drivers embedded, AFAIK, and the Caseta is not a driver, it's a dimmer. So there's no driver in the system to worry about. If we were talking about a dimmable LED bulb, that could be another story, depending on the bulb. But we're not.

The Caseta is almost certainly a phase control dimmer, rather than a high-frequency FET type. I'd gladly bet on that at 100:1 odds, maybe less boldly at 1000:1. 

So I stand by my original post.


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## PhotonWrangler (Oct 20, 2018)

As a test, add a small incandescent lamp to the same circuit and try it again. Some dimmers don't work correctly unless they see a certain minimum resistive load.


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## icedawg (Oct 21, 2018)

thanks for the replies.

They are 12V strips, connected to a power supply that plugs into a standard 120V outlet.

Does that make a difference regarding the suggestions that have been made?


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## MeMeMe (Oct 21, 2018)

YOU were saying 




DIWdiver said:


> Of course it's an AC voltage strip. If it weren't, the Caseta wouldn't work with it.
> 
> LED strips don't have drivers embedded, AFAIK, and the Caseta is not a driver, it's a dimmer. So there's no driver in the system to worry about. If we were talking about a dimmable LED bulb, that could be another story, depending on the bulb. But we're not.
> 
> ...


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## MeMeMe (Oct 21, 2018)

icedawg said:


> thanks for the replies.
> 
> They are 12V strips, connected to a power supply that plugs into a standard 120V outlet.
> 
> Does that make a difference regarding the suggestions that have been made?




The best solution, albeit maybe not one you may like, is to add a small incandescent bulb in series. Then again it may not even go as deep. Unfortunately, there is probably not a lot you can do.


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## DIWdiver (Oct 22, 2018)

MeMeMe said:


> YOU were saying



He never mentioned a power supply.


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## DIWdiver (Oct 22, 2018)

icedawg said:


> thanks for the replies.
> 
> They are 12V strips, connected to a power supply that plugs into a standard 120V outlet.
> 
> Does that make a difference regarding the suggestions that have been made?



Yes, that makes an enormous difference.

So you have 12V strips plugged into a power supply that's plugged into a socket that's controlled by a dimmer? 

Do you have a model number for the power supply?


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## Ken_McE (Nov 4, 2018)

What if you add your own rheostat in between the diodes and the power supply?


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## MeMeMe (Nov 8, 2018)

Ken_McE said:


> What if you add your own rheostat in between the diodes and the power supply?




I believe you mean in parallel with the LEDs to bleed off some of the current? That would make the bottom end dim a lot more, but would reduce the top end. However, if it dims to 10% current now, and you use the rheostat to get to 1%, the top end would only lose probably about 12% (higher voltage, same resistance). You probably would not even notice that. If you use a current source, you would make it a consistent 9%.

There are somewhat simple ways of doing this electronically so it only happens at the low end, but not something you will find off the shelf.


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## Keitho (Nov 8, 2018)

Might be too simple--cut the strip, and add a switch. When the switch is closed, all the LED operate (call that "high mode"); when the switch is open, only a short section light up and provide a lot less light. I can imagine a lot of situations in which that wouldn't work for your interior design constraints and electronics skills, but just in case...


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## KENN MOSSMAN (Nov 22, 2018)

Ken_McE said:


> What if you add your own rheostat in between the diodes and the power supply?




Either one or more silicon power diodes or Schottky power diodes *OR *high wattage resistors. That is very brief....details upon request


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## MeMeMe (Nov 23, 2018)

KENN MOSSMAN said:


> Either one or more silicon power diodes or Schottky power diodes *OR *high wattage resistors. That is very brief....details upon request



All of which reduce the maximum current ... Op doesn't want that.


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