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LED recommendation needed — Parallax Forums

LED recommendation needed

MJHanaganMJHanagan Posts: 189
edited 2014-07-21 11:58 in Propeller 1
I am looking for a recommendation for some LED lights. I want to install them under my kitchen cabinets as task lighting. Ideally these would be some type of RGB LEDs so I can use the Propeller to adjust the color of the light from warm to cool white as well as the overall brightness.

I have five cabinets ranging from about 12" to 40" wide. We had a set of halogen lamps in our last kitchen with roughly 20 W per linear foot, so about 200 lumens per linear foot. These we on a fixed three-level dimmer switch so you could turn then down for accent lighting. These worked well but they got real hot especially in the summer months. Going LED would minimize the heat output and if I use a Propeller to drive them I could do sorts of nifty things (voice activation, auto off at night, auto on in the morning, color changes, infinite brightness control, etc.) My initial thought is to use some of these "LED strips" but wondered if there might be anything better for this particular application. Can you get a warm white light using RGB LEDs?

Any recommendations?

Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-07-20 14:40
    Which LED strips? There is no link. If you are talking about the ones on EBay there is a thread about them somewhere here. I will see if I can find it and post a link unless someone beats me to it.
  • MJHanaganMJHanagan Posts: 189
    edited 2014-07-20 16:00
    NWCCTV wrote: »
    Which LED strips? There is no link. If you are talking about the ones on EBay there is a thread about them somewhere here. I will see if I can find it and post a link unless someone beats me to it.

    Something like this: https://www.sparkfun.com/products/12027

    Are most of these RGB LED strips the same?
  • TubularTubular Posts: 4,703
    edited 2014-07-20 16:28
    My advice would be to go with the addressable strips, because they're easy to drive directly from a Propeller or other microcontroller, and they give you full control. That doesn't mean you have to go crazy with jarring patterns - you can still have smooth, rolling startup and shutdown (analogous to those smooth self closing kitchen drawers).

    Yes you achieve "warm white", just turn down the green and blue a little more than the red.

    Once you get into these you'll find all sorts of other applications too

    I've been experimenting a bit with 'beamforming' using a laser cut 12mm acrylic rod with notches/lenses at the same pitch as the ws2812b's. Looking promising so far...


    Edit: The addressable strips are generally slightly different with respect to timing and pins consumed. The WS2812 and WS2812B are driven using identical single wire protocol and there are good propeller objects already for these. There are clones which accept the same protocol.

    The WS2801 and WS2821 are a bit more complicated to connect. I'd start with the WS2812 or 2812B unless you want to do "PoV" (light painting etc)
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-07-20 16:34
    MJHanagan wrote: »
    Something like this: https://www.sparkfun.com/products/12027

    Are most of these RGB LED strips the same?

    Do you really need/want them to be individually addressable? (I hope the answer is yes but I'm not sure why.)

    If you want to use WS2801 controlled LEDs, then the Propeller would work fine. I used JonnyMac's driver in my "Mood Enhancing LEDs" project and I also use this LEDs on my hexacopter but I'm not sure if they're really the best choice for kitchen lighting.

    I know there are RGB strips where all the LEDs are the same color. I would have thought this would be good enough for your needs. I'm pretty sure the individually addressable LEDs cost more than having all the LEDs the same color.

    Besides the WS2801 controlled LEDs there are also WS2812 LEDs (aka NeoPixels). The WS2812 also work great with the Propeller (using another one of JonnyMac's drivers). I documented some of my experiments with WS2812 LEDs in this thread.

    There are of course lots of other threads dealing with these sorts of LEDs but I usually just keep track of my own stuff. Speaking or which, I've wondered about using RGB 8x8 arrays as lighting. Not very practical but then the lights could double as a text display. (Yeah, I think it's a bad idea too.)

    Edit: I see Tubular beat me to the WS2812 option.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-07-20 16:44
    As I think about this a bit more, I'm not sure I like the individually addressable option for room lighting. The problem with WS2801 and WS2812 solutions is you lose color depth as you turn the brightness down.

    I now remember, this why I was wondering about using the 8x8 arrays. The 8x8 arrays use a shift register to control the individual lights and this shift register has an enable pin. By pulsing the enable pin (PWM) the brightness level could be adjusted independently from the color resolution.

    I doubt you'd want 8x8 arrays but some way of controlling the brightness without limiting your color range would be very useful.
  • lanternfishlanternfish Posts: 366
    edited 2014-07-20 17:11
    MJHanagan wrote: »
    I am looking for a recommendation for some LED lights. I want to install them under my kitchen cabinets as task lighting. Ideally these would be some type of RGB LEDs so I can use the Propeller to adjust the color of the light from warm to cool white as well as the overall brightness.

    With RGB strips it can be difficult to obtain white light that is either too blue or too red. I would suggest parallel strips of warm white and cool white LED. All you need to then do is vary the intensity of one or other to get the colour temp you want. I am currently doing this for a production which requires a 4m diameter circular 'ceiling' to be lit warmly (past and present) and coolly (future).
    I have five cabinets ranging from about 12" to 40" wide. We had a set of halogen lamps in our last kitchen with roughly 20 W per linear foot, so about 200 lumens per linear foot. These we on a fixed three-level dimmer switch so you could turn then down for accent lighting. These worked well but they got real hot especially in the summer months. Going LED would minimize the heat output and if I use a Propeller to drive them I could do sorts of nifty things (voice activation, auto off at night, auto on in the morning, color changes, infinite brightness control, etc.) My initial thought is to use some of these "LED strips" but wondered if there might be anything better for this particular application. Can you get a warm white light using RGB LEDs?

    You could try and source LED replacements for the halogen lamps. This will limit what you will be able to do, of course.
  • MJHanaganMJHanagan Posts: 189
    edited 2014-07-20 19:16
    lanternfish wrote: »
    With RGB strips it can be difficult to obtain white light that is either too blue or too red. I would suggest parallel strips of warm white and cool white LED. All you need to then do is vary the intensity of one or other to get the colour temp you want. I am currently doing this for a production which requires a 4m diameter circular 'ceiling' to be lit warmly (past and present) and coolly (future).

    I'm in a new house and starting with a clean slate so wanted to do something fun and practical.


    You could try and source LED replacements for the halogen lamps. This will limit what you will be able to do, of course.

    Hmmm, I would like to dim a warm RGB white light and for fun do some "holiday" colors for the kids. I'm thinking of my daughter being able to say "pink please" or "red and green" and have the lights respond accordingly.
  • lanternfishlanternfish Posts: 366
    edited 2014-07-20 21:03
    MJHanagan wrote: »
    Hmmm, I would like to dim a warm RGB white light and for fun do some "holiday" colors for the kids. I'm thinking of my daughter being able to say "pink please" or "red and green" and have the lights respond accordingly.

    In that case I would buy a short length of RGB, Cool and Warm and have a play and see what you favour most.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-07-20 22:53
    being able to say "pink please" or "red and green" and have the lights respond accordingly.
    It sounds like an EasyVR may be in the mix also! Duane Degn has done some good work with a driver. I do not think it is finished but he and I have both played with one in the past and it is quite fun.
  • Mag748Mag748 Posts: 266
    edited 2014-07-21 11:58
    Sparkfun offers an RGB Strip that isn't addressable https://www.sparkfun.com/products/12024 and in the description specifically states it can be used for "under cabinet lighting in your kitchen!". The constant current driver might to easier to design than dealing with the serially controlled LEDs.

    Thanks,
    Marcus
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