Dimmer switch for LED flood lights? (1 Viewer)

[estoddart]

Hey all, I'm about to install my new Gobi roof rack and add LED lights bars up front in rear and side angled. I've found the the light bars are great for driving but way to bright for around camp. I'd love to wire a dimmer switch in to tone them down. Has anyone done this yet? I'm not looking for a big $$$ SPod controller just a way to turn the lights down. Thanks

 

[Alban]

Evolve lrm-as work very well w led dimmable bulbs. I have tested them w 3 popular brands. They do require a neutral.

 

[george_tlc]

Evolve lrm-as work very well w led dimmable bulbs. I have tested them w 3 popular brands. They do require a neutral.

Yeah, I'm sure a mains AC dimmer will be real useful for the OP's **12V DC** based LED lights... Duh!



The issue with dimming most light bars etc is that they use a DC : DC constant current driver to take the 12V DC and drive the LEDs with the appropriate voltage/current. So, to do it "right" the driver in the light bar should have a PWM input to allow a PWM controller access to turn the LEDs on/off quickly to provide the dimming function (varying the on/off duty cycle fast enough that you can't see the flicker).

Most of the light bar drivers I've seen can't handle their power being turned on/off quickly (pwm) AND you can't just drop the voltage to dim them since their DC : DC converter will just compensate.

I design a series of LED drivers for a customer that builds quality motorbike lighting and the drivers have dedicated optically isolated PWM inputs that can take input from a separate PWM controller that provides the end user dimming control. The dimming feature is well appreciated by his customers since you don't always need blinding bright lighting.

Seems pointless to have high power LED lights if you can't dim them, but it appears many manufacturers don't consider that a useful feature (yet...).

Unfortunately unless you luck out and find something that just happens to work with your light bar your hope of a simple dimming solution isn't going to happen.

cheers,
george.

 

[estoddart]

Thanks George, good info.

 

[Fast Eddy]

I've been thinking about experimenting with running one of my cheap LEDs with 12v pwm input, just to see if it would work. They're way too bright around camp. What do you think would be the result of a 100hz 50% duty cycle. right into the 12v input of the converter?

I'd love to take one apart to see what const current chip is in them, but they're sealed up tight.

 

[george_tlc]

I've been thinking about experimenting with running one of my cheap LEDs with 12v pwm input, just to see if it would work. They're way too bright around camp. What do you think would be the result of a 100hz 50% duty cycle. right into the 12v input of the converter?

I'd love to take one apart to see what const current chip is in them, but they're sealed up tight.

Any high power LED 'light' would use either a buck, boost or buck-boost current regulated driver so it all depends on how the driver deals with power being interrupted at the specific frequency and duty cycle. Things like soft start circuitry could delay the time it takes the driver to fully power up and so could have interactions with the PWM frequency/duty cycle. Likely it may also generate a heck of a lot of EMI as well (if that matters and you have radio, comm gear etc in use).

Anyhow, it'll be a suck it and see situation... AND what may work with one light may not with another.

cheers,
george.

 

[LandCruiserPhil]

I used the remote control with dimming feature below for my LED strip on my awning also on MR-16 flood lamps.

http://www.ledsupply.com/led-driver...rpK5uQcu2EsaedeNblTnjAjfIKpE3EB_9UhoCEJTw_wcB

 

[george_tlc]

I used the remote control with dimming feature below for my LED strip on my awning also on MR-16 flood lamps.

http://www.ledsupply.com/led-driver...rpK5uQcu2EsaedeNblTnjAjfIKpE3EB_9UhoCEJTw_wcB

The white LED strips will dim fine, since they are just set up as 3 white leds in series with a current limiting resistor and then that 'segment' is repeated for the length of the strip (each segment essentially in parallel with all the others). So a PWM dimmer that pulses power on/off will have no problems at all.

The problems occur with some LED drivers that don't like their power turned on/off. They can also make audible noises as their inductors (part of the DC : DC power circuitry) pulse on/off at the PWM frequency.

A dimmable DC LED light will have a dedicated PWM control input or dimming control. Unfortunately most don't have that and so it's just a matter of trying a PWM dimmer like you linked above and hope for the best when it cycles power on/off to the LED light (that has a driver).

cheers,
george.

 

[estoddart]

So what's the worst case scenario for wiring these KAWELL 18W flood lights:
http://www.amazon.com/KAWELL®-2-Pac...8563450&sr=8-1&keywords=cree+led+flood+KAWELL

with the PWM 12V dimmer, http://www.ledsupply.com/led-driver...rpK5uQcu2EsaedeNblTnjAjfIKpE3EB_9UhoCEJTw_wcB

???

 

[george_tlc]

Worst case it won't work and you'll have to run the lights without the dimmer.

Try it and get back to us. It's not like you're risking much $.

cheers,
george.