According to Pete Episode #40 - Home LED lighting and the SparkFun FemtoBuck

Director of Engineering Pete Dokter is back for another episode of "According to Pete"

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He's back! In today's episode of "According to Pete," SparkFun Director of Engineering Pete Dokter is taking a look at homelighting solutions and the SparkFun FemtoBuck LED Driver. Give it watch:

If you're looking for the LEDs Pete uses, you can find them here. As always, feel free to leave any questions or comments below and we'll do our best to help you out! Hope you enjoyed this episode and we'll see you next month with more "According to Pete."


Comments 29 comments

  • A nice follow up on this would be to go over boost regulators and then maybe the buck boost. I have a few projects in mind that i think would work better with buck boost regulators rather then the standard buck. Thanks for the New video!

  • Pete,

    You did a wonderful job on lighting your kitchen, and the sound was great too. For your next video, how about showing us how to improve the acoustics on the stage that is used for the weekly new products video?

  • How did you pack and orient an LED unit roughly the size of a quarter into a 3/8" channel? Was it necessary to trim off non-conductive base material? Thanks.

  • Thanks for the video. Maybe tone down the pretend ADHD movements/ wannabe teenager sound effects, it really detracts from the great info.

  • Pete, are the femtos wired in parallel around the kitchen?You have many strips, so I assume each one is parallel of each other? And secondly, I assume the strip is brighter if you have fewer LEDs since 350mw/n?

    • Each Femto drives 5 LEDs. Each strip of 5 + Femto are powered from the same power supply. And no, removing LEDs will not result in a change in brightness. Since the output of the Femto's is a constant 350mA and all the LEDs are in series, the brightness of any given LED will always be the same, whether you're driving one or 5.

  • Nice work! Q: Where did you mount/put the power supply? Q: How did you link all the different cabinet segments together? Q: With 5 LEDs tied to each buck, did you just tie all of those back to the single laptop power supply?

    Suggestion: Instead of a manual switch, why not add an Arduino Pro Mini (or something else) and use a PIR as the switch. Just wave your hand under the cabinet and poof turn them all on. I did this for a headboard light, works nice.

    • A: PS in the cabinet above the nuke. A: Correct.

      And I offered to do something fancy with the turn-on sequence. My wife didn't want anything to do with it.

  • I did just this, except I used a light strip from LumiLEDs, the L235 series (Mouser carries them). These are adhesive-backed flex strips, but with lighting-grade LEDs. They drop about 18V each at 600 mA. I coupled this with a Meanwell APC-series LED constant-current supply (also available at Mouser). You could also use the PCD-series, which is triac-dimmable, and has unity PF, but costs a bit more.

    I picked a 2700K LED strip for the kitchen lights, and they look very nice. My workbench light is the same thing mounted inside an old Ikea table lamp, and with 3500K LEDs.

  • Ah perfect timing for this! I've been working on the same sort of project, I recently did a cool white LED strip under the cabinets, which was amazing.

    But the microwave, and above the stove still uses silly incandescent bulbs. I've got some 3W "Cool White" LEDs and some aluminum from Home Depot as well to put it all together! I might just have to get me a Femtobuck to regulate the LEDs.

    How did you mount the LEDs in the C-Channel piece of aluminum? I'm considering using thermal adhesive, but that seems really irreversible, nuts and bolts work well but it's a significant amount of drilling.

    • Two holes on either side of the LED, wires inside the channel, LED on the other. They're not permanently mounted, just held by the tension of the wire. I'm not in favor of making it more complicated than it needs to be.

  • Nice video! It's the very first one that I see, but I will definitely see them all in the weekend. I just have one little question. I'm a newbie but I'm the curious type of person. What about cleaning-waterproof problem? I mean, at the kitchen everything gets messy when I'm cooking (I'm a little clumsy) and I'm afraid that maybe the strip will get dirty. I assume that the holes you have in the aluminium case are just that, holes. Is it going to get all rusty?

    • Well, aluminum won't rust. As far as splash proofing/resisting for ease of cleaning up, Pete didn't show anything.

      • You know, I'm not convinced it's a real problem. If we need to clean, some 409 and a paper towel, not a bucket of water. Will it short an LED? Maybe, but the Femto still limits to 350mA, so I'm not particularly worried about damaging anything... as long as at least one LED in the chain remains operational. Being that they're spaced 7 inches apart, somebody would have to work awfully hard to short them all.

        • But if one LED fails as an open (like from over-aggressive cleaning to get that dried on blob of food off a LED), wouldn't the entire strip go out? The old Christmas tree string problem?

          Not a problem, per se, but a design quirk. ;-)

          • Yeah, the whole strip would go out, but I just don't believe you could get it one LED to fail as an open by cleaning it in the manner you suggest. You'd have to be cleaning it with a hammer.

            As far as design quirks go, there's a million ways to skin a cat. Given that it's a failure mode that I don't believe I'd see in my lifetime in the house, and that replacing one of those LEDs is a 2 minute job... meh. If it fails when I'm 90, you can have gloating rights.

  • Great explanation Doc Pete! Thank you! If i might "Me Too" for a moment: I am currently doing roughly the same thing with my desk. Tried using the strip LED's from the hardware store - but these use the LEDs as rectification to keep the part count down. I can really "feel" the 60Hz - especially when i have a migraine headache. So i wanted to use a more CW light/voltage source. Also, quick changes in brightness are an issue. So I use the Redboard to slowly fade in and fade out the lights using the PWM into the FemtoBuck (a very neat device!). With the instructions and parts from SparkFun, i can make something that more closely matches my "special" needs. Very cool! Mark

  • Nice work Pete, the lighting looks great. I also recently installed some LED lights under my cabinet but ended up using those waterproof LED strips.

    • As did I. I used a 12V power brick, and then a 12V DC rocker switch to a 12V LED strip. All temporarily tacked up so I can remove it easily and with little evidence when I leave this rental. All the wiring that is exposed under the cabinet is 12VDC, not wall AC for safety.

      The downside of my implementation as far as energy conservation is the power brick is always on, I only switch the 12VDC.

  • Pretty cool... Coming to a work bench near me. Also glad to see the kiddo's are well vitaminized as well. We force the same one's on our mini me's. Odd what you notice when you are "invited" into someone else's home.

  • I definitely want to do this. Out of curiosity, where did you hide your power supply? I'm assuming above the microwave?

    • Correct. There's already an outlet there for the nuke. I spliced the power cord down to 6 inches and ran the hot lead down the inside of the cabinet, hot-glued the switch underneath, and covered it all up with 1/8 ply from an old airplane kit.

  • Pete, the Femtobuck and LED lighting was what I have been searching for, to light my work bench area.

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