Incoming!


Ahhhh, October. Fall is in the air, football season is in full-swing, and pumpkins and corn cobs are flying through the sky as if launched from a M198 Howitzer.

Yes, you read correctly. A few weekends ago, a group of SparkFun employees were on hand as Jon Dory from Something From the Farm demoed his corn cob cannon and his pumpkin launching trebuchet.  That is some heavy artillery!

We first got wind of this arsenal when Landon Cox, long-time customer turned supplier, mentioned a pumpkin trebuchet up in Ft. Collins, CO. It turns out Jon (the monster trebuchet creator) was actually a new SparkFun customer after needing a PIC relay board to control his amazing corn cannon. We got to try out his maize launcher first-hand, and let me tell you - it is a sight to behold. At the touch of a button, the corn cannon uses compressed air to launch a whole corn cob up to 300 feet. Amazing stuff!

http://www.sparkfun.com/images/newsimages/corncannon-S.jpg
Jon is ready to lead the veggie revolution with his arsenal of agri-weapons!

Landon suggested we use the trebuchet (and a pumpkin) to test the crash worthiness of his hardy chameleon enclosure. After much prodding (aka, mentioning it to us once), we agreed.

http://www.sparkfun.com/images/newsimages/tre-S.jpg
Bombs away!

Built just like its counterparts from the Middle Ages, this device uses the laws of physics (and 650lbs of concrete counter weight) to propel pumpkins hundreds of feet through the air. As if we needed another excuse to launch gourd-like projectiles, we took a record of the data from the launch using a custom-built accelerometer made by Director of Engineering Pete Dokter and a GPS tracker made by Landon. Check out these graphs of what these poor pumpkins go through.

http://www.sparkfun.com/images/newsimages/treb1-S.jpg

http://www.sparkfun.com/images/newsimages/Treb2-S.JPG

After launching a bunch of pumpkins, we decided to try launching an out-of-commission phone. Pointless? Probably. Entertaining as heck? You bet. Check out this video compilation of the day!



We’d also like to give a plug to Something From the Farm. We recommend them for all your jack-o-lantern needs. Not only do they have a great selection of pick-your-own projecti…er…pumpkins, they have some sweet corn mazes, bonfires, hayrides, and will let you try out the trebuchet. Plus, to get your adrenaline pumping, their corn maze turns haunted at night! Spooky! Thanks again, Jon!

http://www.sparkfun.com/images/newsimages/pumpkin-S.jpg
Doing a bit of “field” work. Get it? Get it?!? Sigh…sorry.

DSCF3925

Landon Cox also has a great post on the GPS tracking data he recovered and some great analysis of how to cover an enclosure with pumpkin goo.

We are also announcing the SparkFun Hack-o-Lantern Contest. This is a competition to see who can build the best/coolest/most creative “hacked” pumpkin - basically a pumpkin that is enhanced with electronics in whatever way you see fit! Here are the rules:

1. You have to document your build with photos or video and a parts list. We want to see what you did to make your awesome pumpkin!

2. Your project must involve two things: a pumpkin (a real pumpkin, not a fake one and certainly not an alternative rock band) and home-brew electronics (though they don’t have to be bought from SparkFun).

3. Submit your project to marketing@sparkfun.com by 5 PM Mountain Time on October 29th, 2009. Include in your email a link to your documentation.

We will judge the pumpkins and announce the winners on October 30th via our homepage. The prizes will be:

1st Place: $50 SparkFun credit
2nd Place: $40 SparkFun credit
3rd Place: $30 SparkFun credit

May the best gourd-like squash win!


Comments 21 comments

  • Hello,
    I did the carthesian => spherical calculation …
    http://img200.imageshack.us/img200/8379/treb2spherical.jpg
    What is weird is the stable G value before and after the flight is not at the same level … maybe the sensor failed !
    Best regards,
    Thomas Legrand.

  • Why don’t U calculate the pythagorean theorem to graph a total acceleration instead of X Y & Z?

  • It bugs me that nothing this awesome is in the tri-state area, or even the east coast for that matter. Keep up the awesome stuff!

  • Linky to the data:
    http://www.sparkfun.com/Code/TrebLaunch.xls
    The first two tabs are me testing the uLog by holding it in my hand and pounding on my desk 5 times. The second 2 tabs are the launches.

  • Couple of questions - assuming the pumpkin is tumbling - how do you compensate for this in the graph data ? If it rolls over, isn’t Y acceleration for instance going to flip in the data, yet the pumpkin is still going in the same direction ?
    Second, are you accounting for gravity ? subtracting it out to get true acceleration values ? A pumpkin falling at 1 G will show up as zero Gs on the accelerometer right ? This can be misleading if not corrected for.
    I’m working similar projects and it’s never as easy as it first looks like it’s going to be.

    • OK, my bad. It’s GPS data not 6DOF type stuff. Still the GPS is only a 10Hz sensor at best. Which means you will miss a whole lot of actual data.
      Anyway, anyone wanting to do this kind of thing with a 6DOF should send me a note. I’m working on code that will do this with the new Razor 6DOF and a data logger. It uses quaternions, to calculate the position of the sensor relative to a earth fixed frame. scott@activergo.com

  • Use the accelerometer to track how fast your pumpkin gets smashed on the street.

  • u guys in colorado have all the fun!!!!
    im coming back out there in a few years….
    well do some stuff.
    got big plans in colorado.

  • Hi,
    You guys are lucky, that’s fantastic toys ;)
    Can you send me the accelerometer’s row data, I’d like to play with in Excel :p
    Best regards,
    Thomas Legrand.

  • I want to see them CATCH the pumpkin

  • What do you get if you plot sqrt(x2+y2+z2)?

    • It looks like there was an offset added to get the initial acceleration to zero - that makes it a lot harder to interpret this data. I want to see the graph with the offset taken out!
      Anyway, if we had a plot of the raw data, this would be a great example of wobbling/nutation. The pumpkin seems to be spinning really fast on its axis (enough that there is more than 1g of acceleration during free-fall), but the axis that it is spinning around slowly shifts around during flight.
      I am also skeptical of the scale of the second graph - was it really spinning enough to deliver 20+ g’s? And what’s with the huge acceleration after it has landed?

      • Hey Paul,
        Offset? …yeah, I’m not sure why I did that. Maybe to make it look prettier. In any case, I’ll post the raw data in our code section sometime today.
        As for data interpretation, I’m just giving you what the sensors told me. I can weed my way through kinematics when necessary, but I’m certainly no master. Two things to consider are that 1) the second launch was, well, the second launch and who knows what may have been compromised, and 2) the second launch was performed with Landon’s box (the first was just the uLog), so the pumpkin was heavier and the uLog was likely farther from the center of rotation. And yes, it was crazy-spinning.
        The huge acceleration is where the z-axis failed outright.

  • I dont understand the graphs .It takes 9 seconds or so but the video shows about two seconds from launch to hitting the ground. How does this fit together?
    Great stuff of course

    • I think the 9 seconds is the total time. Looks like there is about .75 seconds where nothing is happening, then the trebuchet starts moving and the pumpkin is in the sling but in motion, then in the air for a period of time, before hitting the ground at about 7.3 seconds and then rolling to a stop at at 8.5ish.
      At least that’s what I’m gathering from the graph!

  • I i’m too busy lately but i can’t wait to see updates about this Pumpkins.
    By the way, the last url of the page:
    “May the best gourd-like squash win!"
    It should be linking to here:
    http://en.wikipedia.org/wiki/Pumpkin
    Best regards,

  • is it possible to use a fake pumpkin if our current location excludes us from getting a real one this year. i.e deployed?

    • Absolutely. If you’ve got a good reason for not having a real pumpkin, give us a creative excuse and solution and we’ll definitely consider your entry.

  • I had a great time with Nate, Pete, and Jon doing this. Thanks - it was a gas!
    For yet more amusement you can read more on the story and get the low-down on the trebuchet release mechanism at:
    http://sawdust.see-do.org/gps/files/PumpkinGPS.html
    Landon

  • All I have to say is sweet, only thing cool thing shooting projectiles is potting electronics in them.


This Week

This Month

Heartbleed

Happy Arduino Day!