LED mortar board battles suns brightness with 21W of power

led-mortal-board

[Jeremy Blum] aimed to be the brightest student at his Master’s graduation ceremony this spring. He designed an LED rig for his mortar board which should battle the sun’s intensity by using up to 21 watts of power. But he didn’t stop with eye-catching intensity. while he was at it he also included some interactive features so the guy behind him has a way to keep from going blind.

One thing that really caught our eye is the 3D printed parts he generated for the project. There’s a nice mounting plate for the LED side of things, and a wrist-mounted enclosure for the Raspberry Pi board. Wait, why does he need an RPi to drive some LEDs? We already mention interactivity which is facilitated by the Pi acting as a WiFi hotspot. Connect to the access point and choose a color. If you’re in the seat behind [Jeremy] you’ll want to choose black! All of this and is explained in his video presentation.

Comments

  1. Gert says:

    Next up we can have the “Immortal board”, with this on top!

    (They’ll probably fix it, but the initial title was “LED mortal board…”)

    (Hmmm. I haven’t even read the article. I’m just a horrible grammar troll I guess :/)

  2. SpikedCola says:

    “… Up to 5.6 amps of power.”

    The article states, “It is equipped with a total of 16 350mA high-brightness LEDs (4 each of Red, Green, Blue, and White). The PCB is fed 15V and drops it over each of the 4 LED colors in series (4 parallel strings of 4 LEDs).”

    350mA per string x 4 strings = 1.4A, minus the drop across the current sharing resistors. Plus a RasPi, Wifi and LCD display, maybe 1A.

    I count ~2.5A. Where does the rest come from?

  3. zaprodk says:

    The amount of Amps dissipated in the LED has absolutely nothing to do with the brithtness… Just sayin’…

    • Pedro says:

      The Amp is also not a unit of power.

    • SpikedCola says:

      Sure it does – take a 350mA LED, heatsink it and put 700mA through it. It won’t last quite as long but you’ll get ~1.6-1.7x the light output.

      • Dax says:

        No you won’t because the thermal load quadruples with doubling of current. Halving the difference between heatsink temperature and ambient temperature requires doubling the heatsink, or doubling airflow etc. That means the temperature of the heatsink can only get so low even with ridiculously large heatsinks because of diminishing returns.

        So the bottleneck is the thermal interface from the LED junction to the heatsink, and doubling of current and quadrupling the heat load will cause a near-fourfold increase in junction temperature over the ambient, and the LED will overheat and dim within seconds. Permanent damage occurs within minutes. That’s why you don’t run LEDs at double their rated current.

        • Rick says:

          It’s a diode, not a resistor. Doubling current will only increase dissipation power by slightly more than 2x. Please try to be right next time you correct someone.

          • medix says:

            If I were you, I would read the datasheet and perhaps read up on thermal de-rating before counter-counter correcting another post. ;)

          • Dax says:

            The forward voltage of the LED junction increases a lot with increasing current and is highly variable depending on the exact part, which means your power dissapation is not as linearily related to the current as it tends to be in small signal diodes: http://files.leds.co.uk/images/news/archive/figure1.gif

            It’s not quite a power of two relationship, but the higher temperature also increases the ohmic resistance in other parts of the chip, like the bonding wires, which also leads to increased heat dissapation inside the chip.

    • fartface says:

      How cute. Someone here doesn’t know Ohms law.

      Just Sayin’…

  4. M H says:

    I assumed that a mortal board would incorporate some form of “memento mori” (perhaps replacing the slave walking behind you with a recording).
    “Respice post te! Hominem te esse memento! Memento mori!”

  5. Noagels says:

    silly americans with their silly hats

  6. Alex Rossie says:

    Amperes area measure of current. Not power (measured in Watts).

  7. Jean says:

    I need this guy. When I go to beach wifi spot + light for the night. Can he play music?

  8. Horace says:

    Came for the Amps != power comments. Leaving satisfied :)

  9. vonskippy says:

    Crazy kids and their liberal Uni’s these days. When I graduated it was a solemn occasion while we stood around and waited for our stone tablets to be chiseled with our name and degrees.

  10. mikeayles says:

    Not sure why he used a usb-ftdi cable, he says the light control was done by an arduino clone, which I’m assuming to be a bootloadered atmega, so why didn’t he just use uart on the gpio? There’s no need for it to be particularly quick, 9600 should be plenty for a few bytes, so it could have been bit banged if necessary.

  11. Apex1302 says:

    This is usefull to prevent people from saying:”he might have a degree but he is still not not the brightest bulb/LED on the porch” ;-)

  12. Protolamer says:

    Aww come on man, it’s your graduation not Burning Man or Maker Faire…

  13. NewCommentor1283 says:

    when i get the money…
    you wont see me…
    you will think you are walking into the light…
    then i will say “excuse me?”
    … and “the light” will take a step back

    XD couldnt help it, awesome hatrick

  14. echodelta says:

    In Texas, mortar would be the V8 in your pickup.

  15. Mike says:

    This guy must have SO many friends.
    I bet his killer graduation caps attract all the girls.

  16. luke says:

    Doesn’t seem overly lethal to me. [Scnr]

  17. mr midnight says:

    Jeremy is a cool kid. Does a lot for open source/diy community with his videos and blog and I can see CEO’s of companies following his tutorials on a Sunday afternoon.

    Great to see he graduated. And another cool project.

  18. jalousier says:

    Hi guys! Let me take a minute of your time.
    Our young startup has developed a revolutionary product for automation of existing window blinds. It is Wi-Fi and ZigBee enabled. We have launched a Pre-Order campaign today – please like, share and contribute!
    Check out the link below: http://bit.ly/1bkbCHh

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