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Old 10-09-2013, 10:30   #1
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LED Dimming - help needed

I've upgraded my lighting with LED's throughout. I have some strip lighting which I have wired through a PWM dimmer...so far so good. I also have 12v MR16 bulbs which work well through a household-type on/off switch.

I have purchased some 12V PWM household-style dimmers LVDx-100W LED Dimmer for Standard Wall Switch Box | Dimmers | Installation/Power Supplies/Misc | Super Bright LEDs and wired them to MR16 12v bulbs, however at low dim the bulbs start blinking and then the dimmer fails and has to be trashed. I can't figure out what is going wrong as I am reasonably certain that they have been wired correctly. There is no over-voltage and the dimmers are only wired to a couple of bulbs using less than 2amps.

I realize that these dimmers are cheaply made but they are the only 12v LED dimmers that I have found which are presentable enough to install in a wall plate on a houseboat.

Any suggestions are welcomed.
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Old 10-09-2013, 12:53   #2
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Re: LED Dimming - help needed

It might depend upon the bulb(s) being dimmed.

This MR16 bult is listed at not compatible w/ dimming. Most other MR16 bulbs are rated for dimming.
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Old 11-09-2013, 12:12   #3
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Re: LED Dimming - help needed

Yeah some LED's will not respond well to dimming others will only accept certain frequencies of PWM. Usually to avoid problems we spec dimmers from the lighting manufacturer (such as IMTRA or I2) if not we will request the specs on the light to make sure the output of the control unit matches, other wise you will get erratic dimming and the flashing you mentioned. If your a die hard do it your selfer I have had some luck with using resistors in line on the ground side of the circuit at the light but it's tricky to get the right one and doesn't always work so I wouldn't really suggest it.
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Old 11-09-2013, 12:23   #4
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All LEDs can be dimmed by a variety of methods. However some led assemblies have regulators or led drivers that prevent such dimming

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Old 12-09-2013, 01:57   #5
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Re: LED Dimming - help needed

There looks to be 2 problems here:

Household LED units rated at 12V are designed to be used with a fixed voltage AC transformer or sometimes DC power supply and may not work i.e. fail with the range of voltages on a boat which can go up to 14.8V on charge and higher if equalising. There will also be spikes on the supply line from the back EMF generated from high current devices such as anchor windlass, starter motors and the like which will give transient voltages well above 12V. The units I use are rated 8-30V and do last well. Look for units designed for RVs, Caravans or marine use.

A 12V LED has a built in regulator and they are either designed for dimming or not. You cannot dim one not designed for it.

Sorry if this sounds a bit brutal
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Old 12-09-2013, 02:10   #6
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Re: LED Dimming - help needed

Rapanui, thanks.
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Old 12-09-2013, 09:31   #7
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Re: LED Dimming - help needed

Quote:
Originally Posted by Privilege View Post
I have purchased some 12V PWM household-style dimmers LVDx-100W LED Dimmer for Standard Wall Switch Box | Dimmers | Installation/Power Supplies/Misc | Super Bright LEDs and wired them to MR16 12v bulbs, however at low dim the bulbs start blinking and then the dimmer fails and has to be trashed. I can't figure out what is going wrong as I am reasonably certain that they have been wired correctly. There is no over-voltage and the dimmers are only wired to a couple of bulbs using less than 2amps.
Another idea:

One difference with incandescent bulbs vs LEDs as the load is that when cold, incandescent bulbs present a very low resistance until they warm up. So I'm thinking that the initially high current into the cold MR16s is too much for the dimmer.

Also, if the if the bulbs are visibly blinking at low dimmer settings, that suggests that the load forms part of, or at least affects the dimmer time constants, so that's another indication that these dimmers just aren't suitable for use with incandescent bulbs.

Here's just one example of a 12 dimmer
that can handle incandescent lights.
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Old 13-09-2013, 17:07   #8
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Re: LED Dimming - help needed

Thanks guys, I appreciate your input...Rapanui, you're not being brutal; I wouldn't have asked if I didn't want the answer!!!
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