led_bulbs.jpg

Tim writes in:

What are the reasons we see light bulbs made up of lots of small LED’s instead of one large LED?

As Collin showed us in his excellent video about the subject, LEDs pass electricity through “dies,” or little chips cut from a larger wafer of semiconductor; there is just a small active area that’s actually lighting up, which is then reflected out in the desired direction. Engineers try to make the most efficient LED possible, which is linked to the size of this semiconductor as well as the heat it puts out, among other things. There is such a thing as a multi-die package, which puts more than one piece of semiconductor inside the same plastic casing. My favorite electrical engineer, Matt Mets, found me this interesting article comparing the efficiencies of single-die and multi-die packages for LEDs. Essentially, the maximum usable size of the semiconductor is limited, and there’s a limit to how many you can cram into one lens before the thing generates too much heat. On the practical side of your question, the market is just now seeing a boom in these “bulbs” containing many LEDs, like the one pictured above (image from Treehugger). The product designers for these things are buying off-the-shelf components and putting them together into a product, not engineering new LEDs… yet. We’re able to see a massive reduction in energy consumption with these LED bulbs when compared to incandescents, so the demand for an even more efficient model (perhaps using multi-die LEDs) hasn’t quite caught up to us yet. The takeaway: bigger isn’t always brighter!

 

Young maker Justis writes in:

I’ve just started out in electronics and I want to make some cool stuff! but alas, being a kid and all, I don’t have much time to bike to radioshack every time I need a resistor. How do you recommend I start gleaning things for projects?

Simple: you’ve got to build up a stash! Components aren’t that expensive, especially resistors. I’d recommend asking family members for gift certificates to Sparkfun, the Maker Shed, and even Amazon, which all carry excellent components and kits, and they’ll mail them right to you, no bike-riding required (work with your parents to ensure you’re buying form a reputable site). If you come across older devices at the thrift store, like VCRs and the like, they often contain full-size (not surface-mount) components that you can remove while you practice your de-soldering skills. When I was a kid, I was really into baking, so for every gift-giving holiday, I’d ask for a different item that I couldn’t afford myself, namely a stand mixer. If you make a wish list for those who might shop for you, include web addresses for particular products to ensure your non-savvy relatives get you the things you really want. To start with, I’d highly recommend the DIY Design Electronics Kit by Sparkle Labs. It comes with a great starter assortment of many different types of components in common varieties, so you won’t have to ride over to RadioShack quite so often. Show us what you make!

If you have additional advice for Tim or Justis, leave it in the comments! And if you have a question for MAKE about a project you’re working on, concept you’re trying to understand, or anything else related to the complicated life of makers, drop me a line at [email protected] (or record a video, tweet at us, etc.).

Becky Stern

Becky Stern

Becky Stern (sternlab.org is a DIY guru and director of wearable electronics at Adafruit. She publishes a new project video every week and hosts a live show on YouTube. Formerly Becky was Senior Video Producer for MAKE. Becky lives in Brooklyn, NY and belongs to art groups Free Art & Technology (“release early, often, and with rap music”) and Madagascar Institute (“fear is never boring”).


  • KentD

    First, get one of those plastic parts boxes with 10 or 20 small drawers about 2 inches wide. You might find one at a thrift store. Mark one group of drawers with colors corresponding to the multiplier band on the resistors, brown, black, red, orange, yellow, etc.
    Then order an assortment of resistors like this one for $9.95:
    http://www.gatewaycatalog.com/cgi-bin/category.cgi?category=1700
    or at Radioshack.com:
    Catalog #: 271-003, 500 resistors for $12.95.
    Catalog #: 272-802 capacitors
    Catalog #: 272-801 ceramic capacitors
    There are other dealers with similar packages, like this one:
    http://www.smcelectronics.com/grabag.htm
    although they don’t have resistors.
    The other way to get parts is to recycle. Find any old electronic device, and desolder parts. Just don’t breath the fumes. Lead is not good for you. I have even seen people use a torch to gently heat a large area of a board, and then whack the board to shake out the parts.

  • jschuch

    Collect junk!

    Seriously, let everyone that you know that they are not allowed to throw away anything that plugs into the wall, or runs on batteries. Take it home, tear it apart, and build your inventory. That’s what I’ve done for years, and still do.

    For example, take an old pair of computer speakers (there are scads of them at Goodwill stores and the like for a buck or two). Tear them apart and you’ll probably have…

    A small stereo amplifier
    1 or 2 pots
    a couple of speakers
    an led or two
    a wallwart power supply
    a couple of jacks and plugs, power and audio

    If you desolder the amp, you’ll end up with a handfull of resistors and caps, an amplifier chip, and who knows what.

    This applies to everything from alarm clocks to dish washers. (avoid anything with a CRT in it)

    Check out …

    http://www.hackersbench.com/P4P/p4p001/index.html

    http://www.uchobby.com/index.php/tag/scrounging/

    John

  • jammit

    @Justis
    You can do what I did as a kid (who am I kidding? I’m still a kid, just older). Wait for Christmas, but make sure you don’t ask Santa for anything your brothers are getting. Maybe even convince one of your brothers he’d be better off with a different toy in case the other brother gets the same thing. About three months after Christmas, offer to take all of your brothers broken toys. It’s like getting two Christmases every year.
    You can also use (the Almighty) Google to look for parts you need. Check out the website of the company making the part and see if they have free samples. I actually got an LCD backlight inverter for free and have built stuff for $0. This not only includes semiconductors, but also hardware like free screws and supplies like free solder.

  • Paul

    Re: KentD
    Those are two great sites. I hadn’t come across the “grab bags” before… Very tempting.

    I’ve been building up a stash ordering assortments from eBay. I’ve found a couple of sources that deliver from China who sell good components at bargain prices. Here are two of my favourites:

    Sure Electronics
    http://stores.shop.ebay.com/Sure-Electronics__W0QQ_armrsZ1

    Thai Shop Etc
    http://stores.shop.ebay.com/Thai-Shop-Etc__W0QQ_armrsZ1

  • Joel

    But why on Earth do they use a phosphor built into the bulb? At the very least, they could use a phosphor-coated casing, and then less of the light scattered from the phosphor would be re-absorbed by the die. Ideally, since they have so many LEDs there, they could include many different band gaps and have the light mix in a diffuser. Not only would this mean fewer dice of expensive, wide-gap LEDs, it would mean better, and user-adjustable, color rendition.