Jump to content



Photo

LED Dimming help


  • Please log in to reply
12 replies to this topic

#1 wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 01 October 2012 - 19:31

Probably should look for a real forum about LEDs, but maybe someone on here could help
I am building a Light Fixture, that I hope to have a production run on in the future.
I am using a 5 meter LED strip, cut into separate strips. I want to dim these, however the only info I can find to do this is to use a PWM inline dimmer. This one goes between the power supply and the leds. This is not what I want though. I want to build the dimmer into the lamp, and the PWM switches are too big. I have room for a dial potentiometer though. Does anyone know if those can be used to dim LED strips? How do I find out what potentiometer to look for as far as range goes.


#2 +jamesyfx

jamesyfx

    Neowinian Senior

  • 8,383 posts
  • Joined: 04-February 06
  • Location: Manchester, UK
  • OS: OS X 10.9 / Windows 8.1
  • Phone: Nexus 5

Posted 05 October 2012 - 08:04

Hi,

You can use a potentiometer to control brightness of LED's. As for the range, I would just experiment. Pots are not expensive, just get a few and see what works best.

#3 cybertimber2008

cybertimber2008

    Neowinian Senior

  • 1,738 posts
  • Joined: 02-December 08

Posted 05 October 2012 - 12:27

Get these? http://www.amazon.co...ed+light+strips
They are dimmable, and you can cut them into strips to as small as 3 inch segments.

Edit: Re-reading your post, it might not be helpful, but I wonder if you can use the controller in your design?

#4 OP wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 05 October 2012 - 12:36

I am using led strips already. Its a 5 meter segment cut into 8 strips. Total power consumption will be around 24 watts 2 amps. I am having a hard time finding a pot that is 12v and can handle that kind of wattage. Any suggestions on where to look for one? I have considered a controller, would that be a better route

Secondly as a fall back, I have looked at just using a regular push button switch or even a rotary switch that would turn on various strips and different clicks. I can't seem to find a 12 volt switch that would handle 24 watts, most are just .5 to 1 watt. Would it be possible to use a 125 volt switch on a 12 volt system

#5 Hum

Hum

    totally wAcKed

  • 63,556 posts
  • Joined: 05-October 03
  • Location: Odder Space
  • OS: Windows XP, 7

Posted 05 October 2012 - 12:40

Perhaps here:

http://www.potentiometers.com/

Edited

#6 n_K

n_K

    Neowinian Senior

  • 5,424 posts
  • Joined: 19-March 06
  • Location: here.
  • OS: FreeDOS
  • Phone: Nokia 3315

Posted 05 October 2012 - 12:43

You don't need a 12V pot, you just need any pot thats got a voltage > 12V. Then depending on what brightness reduction you want you select the resitance of it, e.g. a 10 Ohm pot. won't dim it very much but a 1M Ohm will probably have the LEDs completely off without turning the pot much.

#7 OP wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 05 October 2012 - 22:08

I went to that potentiometers.com site and found one that I would prefer to use, and originally was looking for something like this
http://www.potentiometers.com/LT.cfm
Looking at the electrical specs on it, I can't tell if it will work with my led strips described above

#8 n_K

n_K

    Neowinian Senior

  • 5,424 posts
  • Joined: 19-March 06
  • Location: here.
  • OS: FreeDOS
  • Phone: Nokia 3315

Posted 05 October 2012 - 22:48

'Max applied voltage
30 VDC'
It should do, but it's got a minimum resistance of 1K Ohms which is kinda wasteful...

#9 OP wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 06 October 2012 - 01:10

for pots and switches in general, do I need to be looking at the max watts or miliamps rating? I mean being that I will be using about 24 watts of power

#10 OP wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 02 November 2012 - 01:02

Wanted to share the progress
Here is a link to the lamp on flickr


I used a 3 watt rheostat for the dimming, it works well, but doesn't dim all the way down, which turns out fine.

#11 n_K

n_K

    Neowinian Senior

  • 5,424 posts
  • Joined: 19-March 06
  • Location: here.
  • OS: FreeDOS
  • Phone: Nokia 3315

Posted 02 November 2012 - 13:24

That flash thing just loads nothing ? Got a link to the flickr page itself?

#12 OP wv@gt

wv@gt

    Neowinian Senior

  • 4,280 posts
  • Joined: 19-May 04
  • Location: Atlanta, GA

Posted 03 November 2012 - 00:00

Heres the link, if I hyperlink it, the forums will automatically do the flash show

flickr.com/photos/wvangelderen/sets/72157631902499868

#13 greglee

greglee

    Resident One Post Wonder

  • 1 posts
  • Joined: 14-December 12
  • Location: San Francisco, CA

Posted 14 December 2012 - 05:20

Generally speaking, the higher the SMD number, the brighter the light. Also the higher the amp draw.
3528 strip are overly bright for interior lighting......which means 5050 strip would be blinding.
Exterior lighting should be at least 5050s, if not 5630s.

If you plan on using a dimmer, keep this in mind: You need a switching dimmer, not your standard voltage dimmer. LEDs are on/off, with no in-between. That means lowering the voltage ain't gonna do squat. You need to reduce the amount of time the LEDs are lit -- basically, you need to adjust how rapidly they are switched on and off. A switching dimmer will decrease the amount of on/off cycles, increasing the amount of off time between on cycles -- but so fast that human eyes don't detect any flicker, only dimmer light.