Help with cabinet LED Lighting Project

I did a bit of digging but couldn't find anything (apologies if I've missed something). I'm going to dump my thoughts/notes here, so sorry for the long thread. I'm just trying to make sure everyone has what I've got. Also, I love bullets. Sorry. :)

I'm looking at doing an under-cabinet lighting system in the kitchen. The house has existing fluorescent light fixtures on the 'wall-side' of the cabinet from I think 1981 or so. The fixtures aren't very bright and as they sit on the 'wall-side' of the cabinet, they don't really illuminate the work area so much as show you the backsplash of the counter.

  • 11 sections of cabinet to illuminate
  • 6 modules (C1,C2)(C3)(C4,C5)(C6,C7)(C8,C9)(C10,C11)
  • Each module to have on board PIR & Arduino
  • Each module requires power supply from 120vac feed - no wiring in the walls or exposed, using existing wiring
  • Module 1 has onboard clock/battery for time clock.
  • Module 1 has onboard 315MHz transmitter
  • Modules 2-6 have onboard 315MHz receivers

Functionality is pretty simple (I'm skipping the trans/receive aspect for now)

If time =06:00, set "standby" to 0%. During the day, the LEDs should be off or very dim. If time =21:00, set "standby" to 15%. Nightlight mode. If PIR detects movement regardless of time, set "output" to brighten (over a few seconds) 100%. When PIR signal drops out, set 120 second countdown. At end of countdown, dim it back to "standby".

I want these things to actually help illuminate prep work. I got spoiled by commercial quality kitchen lighting. So during the day they should be off, but if you drop a cutting block on the counter and start going, the lights brighten up to help you see what you're doing. When you're done, they return to low automatically. At night, they illuminate for a midnight snack, but then return to low level when you're done. Realistically, I could also set it so at night the countdown timer is like 30 seconds, but that'll only be after the loop is working right on a physical module...

Thoughts so far!

  • I priced out commercial LED lights at the store and that's my budget. I'm doing this for wow factor, but I'd like to not break the bank.
  • I don't really know if it makes more sense to have a clock on each module and skip the R/F nonsense. Cost wise it's not too far off one way or another - I'm just worried about having to change 6 batteries later on down the line as I think the li-po suckers only last 3-5 years and having to plug all 6 into the computer is a pain in my mind.
  • Alternate thought was to use an ambient light sensors on each module - but I think that won't work because the light from the other modules reflecting off the counter would trick the sensor into thinking it was time to dim and they'd all fight off one another. Maybe I'm wrong?
  • ...Or I just forget about the clock nonsense and stick the photo-eye on the module farthest from the rest of the other cabinet lights and make that one the master - though it's also farthest from the main kitchen light and windows, so it might think the room is darker than it is and might cause some goofy things to occur. I don't own a meter to measure lux and can't borrow the one we have at work. :P
  • I was thinking of how much power I could get away with for the lights (knowing the arduino output power is limited) and my initial thought was to go with a 0.5W "luxeon" style of LED through a 2222 on each PWM output, but the 2222 really isn't a constant current source on its own - and as I'd rather not have to worry about the cost/expense of all those LM334/2907s/Luxeons/Optics/Heatsinks I figure go with a 2222 and a couple "bright" 5mm or 7mm resistors with a nice fat resistor and say good enough as they won't care so much about current and temperature. I just don't know what LEDs to go for and how much light I can get my fingers on. I don't really think its possible to get "too much light" in this case...

I was hoping to order components this week and toss a prototype together later this month - if nobody chimes in I'll just order a bunch of stuff and see what happens I guess. I like the idea of the luxeons, but I don't know if there's a better way to do it. A friend already suggested getting the SMD5050 stuff off ebay, but I don't know if they're really very bright if they can get mounted to a flexible circuit like that. Someone must have done this before. Any thoughts? Advice?

Hi, Nice project..

I hate so many kitchens with overhead downlights where you head shadows what you're working on!

Are the cabinets continuous, or broken by refrigerator / other sections?

Are you OK with under-cabinet mounting / wiring within each continuous section? Maybe one Arduino with multiple PIRs can do a whole section.. Also, having the over-sink LEDs controlled by a module a splash distance away might be good...

If you have 2 or 3 sections maybe the Real-Time Clock batteries would not be so much of a problem. The DS1307 RTC does not take any current from the battery if it is powered. Also it can be run in a mode where there is a trickle-charged rechargeable battery.

I agree the simple Switching-transistor and resistor per LED is probably a good idea.

DISCLAIMER: I will mention stuff from my own shop...but that's what I know about.

You might prototype some stuff with Electronic Bricks. This kit has PIR, light sensor, (small) LED, etc.:

A Real Time Clock brick is here:

You will design more compact final systems, but this may be a good way to get started..

Let us know about what you figure out as you go along.. This seems like a good "Stepwise Refinement" project.

The wiring under the cabinet section is fine - the cabinets have a solid 7/8" frame to hide everything I need to really get in there. The sections themselves are also separated by things like the stove and the fridge (and a door). I'd rather not have any aux wiring running around, despite it being a serious headache - especially as once I'm done I can post the files and it'd be easier to adapt to other kitchens.

The sink area itself is in the kitchen with no cabinets above it and is a separate project to illuminate - I haven't even figured that one out yet.

I looked into the DS1307, that might really help to prolong the life of the system... maybe at that point it'd be less of a hassle to do that then have wireless communication master/slave issues... though it does bring up the question of what to do when winter hits and the sun sets much earlier and you want to change the time. If the master module had a built in LCD with three tactile buttons to set the time/cycle, that would eliminate that issue at very least. Downside would be seeing the LCD in the first place, as it'd need to be exposed and not tucked up there.

I've already got the PIR and photo sensors (ebay) and a few clocks running around from another project. The only problem is they have an internal lipo battery and no recharge configuration. So far I've got the basic stuff working (LED dims and brightens, ambient light and motion all work).

I ordered a huge variety of white LEDs off ebay... I'll put together some prototypes and get them working once the different LEDs arrive. I also ordered the trans/receiver combo from sparkfun this week, so I'll start playing with that once it arrives.

The other option I thought of while at the office today was keeping 3 of the PWM outputs for some RGB LEDs (not nearly as bright as the white) and having those be the nightlight function. In theory you could set them so they'd slowly change through a varied color pattern like LED cubes do. As the kitchen counter and backsplash is white and lacking in color, it might make for a more attractive nightlight effect...