In MAKE Volume 18, we published Luke Iseman’s Garduino project. I was always fond of the project because I wanted to find ways to monitor water and light in a greenhouse. In truth, the project was a bit crude. Now Luke, who I met through Maker Faire Austin and has since moved from Austin, TX to San Francisco, has a Kickstarter project to develop an upgrade to Garduino called Growerbot. Growerbot is “way more user friendly,” says Luke.
Photo of Growerbot by Luke Iseman
Growerbot is described on Kickstarter as a “social gardening assistant.” Its new features include:
- a built-in-display, enclosure, and everything else you’d expect from an actual product
- better sensors: collecting data on specific parts of the light spectrum, accurate humidity, etc.
- wifi streaming of plant data.
Luke’s eventual goal for Growerbot, he says, is “to gamify gardening.” “Growerbot will help you grow food in the real world while entertaining your virtual friends with updates from your garden,” he writes on his Kickstarter page. He’s got two backers at $880 for whom he promises to supply “Growerbot Pro.” With 39 backers so far, he’s already exceeded his $5,000 goal with 4 days left.
I’m not sure gardening needs gamification. What I’d like is affordable technology for monitoring and control of gardens and small scale farms that also connects them to the Internet.
Filed under:
Home and Garden,
Outdoors 
By Glen Whitney for the Museum of Mathematics
Last time began a journey through the world of mechanical/mathematical linkages, a journey we take up in earnest today. See the previous column for the MoMath Linkage Kit, an introduction, and general instructions.
If we’re really going to understand linkages, what makes them tick, we should start from the very simplest. And one important way of measuring the complexity of a linkage is its number of “degrees of freedom”. This is basically the number of independent measurements you have to take of it at any given time to pin down exactly where every component is. You can also think of it as the number of “dimensions” in which the mechanism as a whole is able to move. For example, with the scissors jack as we used it last time, you could move the “input” pen up/down and left/right on the page, and that would determine exactly where every other component of the linkage had to be. (That’s why there was a cohesive, reproducible “output” drawing.) So that scissors jack had two degrees of freedom. Adding bars tends to increase the number of degrees of freedom; adding links tends to decrease it. (In fact, there’s a formula quantifying these phenomena, called the mobility formula.)
So, if we’re going to start simple, we should focus on linkages with one degree of freedom. (In fact, almost all of the linkages we’ll look in all have just one degree of freedom.) Another important measure of complexity is the number of bars. So, do we ever use a one-bar linkage? Absolutely: it’s called a compass. You fix one end, and use it to draw a circle.
How about two-bar linkages? Well, if you fix just one joint, a two-bar linkage would have two degrees of freedom, and we’re not up to that yet. And if you fix an entire bar, then all that can happen is the other bar rotates, and you’ve got a compass on a tether…
So, on to three bars. If you fix one bar but don’t link the other two, you’ve got
siamese compasses that can draw two independent circles, not so interesting yet; and if you do link the other two, you have a triangle, which is rigid, i.e., has zero degrees of freedom — not quite enough.
Therefore, the simplest sort of linkage, other than the compass, is the four-bar linkage with one bar fixed, and the other four bars linked in a loop. But as it turns out, the world of four-bar linkages is already incredibly rich. To try to illustrate that, we’ll take a look today at recipe #2:
Complex 4-bar
Ingredients: A 50-rod (A), 25-rod (B), 60-rod with a 45-hole (C), a 35-rod (D), four linking sticks, and a pen.
Directions: Link A to B to C0; link C45 to D back to A. Put a pen in C60.
Your linkage should look like this:
How to use: Rotate bar B, one full turn. Note that at a few points you will have to “hop” one bar over another, because the linkage sticks protrude above and below the joints. Watch as the pen draws an unfamiliar curve:
What is that curve? It’s certainly not a circle, or even an ellipse. Is it an area bounded by two circular arcs? Or an arc of a parabola? No and no. It looks a bit like a whale — maybe it’s the Moby Dick curve? Turns out, it’s a curve implicitly defined by a sixth-degree polynomial in x and y coordinates for the plane (as derived in Hartenberg & Danavit). In fact, a four-bar linkage is presumably the simplest apparatus you could make for drawing sextic curves! Next time, we’ll take a look at what sorts of things one can do with the flexibility afforded by that sixth degree…
More:
See all of our Math Monday columns
Filed under:
Science 
And we’re back with our thirty-eighth installment of Your Comments. Here are our favorites from the past week, from Makezine, our Facebook page, and Twitter.
In response to My Diablo III Sculpture: Azmodan, jamesbx says:
That is very nice work. I do some creepy themed artwork in glass and bronze, and recently started electroforming over rodent bones, then working glass into the final piece. But real rodent spines are somewhat, um, disturbing to work with. I was thinking maybe making a clay model, then making a mold of it, casting plaster in the mold, and electroforming bronze over the plaster duplicates.
It looks like Smooth-on Mold Star is one way to create a mold. Do you use something different for making molds? I'm interested in recommendations for an economical way to do this.
In the piece Brick Challenge: Stop Planning That Big Project, Just Do It!, john machniak remarks:
Your message is a good one, Nick!! I'm always impressed with your interests (a renaissance man!!) and your high-tech, yet high-touch approach to ideas.
In response to Interview with Vela Creations' Abe Connally, Off-Grid Homesteader, user Jared Obermeyer says:
Strangely appropriate that I read this article today as I agreed to purchase six acres of land near where I live. I slowly want to achieve what you have here.
In the piece Announcing the Project Remake Contest Winner!, trkemp says:
"Next up: powering a MakerBot Replicator with energy generated by waste veggie oil to print parts needed to make engine conversion kits. Ahhh now that's meta!"
You left out, "…print parts out of plastic made from recycled vegetable oil…"
In the article NEWS FROM THE FUTURE – 3D-Printed Guns, user rocketguy1701 writes:
Well, actually it's a bit of a overblown non-story really. Anybody with sufficient mechanical knowledge and a few tools can be making guns at home. The 3D printing aspect may make a few parts slightly easier, but it's not a decisive factor, especially since the critical components are metal, not plastic. The buzz is just that 3D printers are new, people don't really understand them yet, and they've been put forth as some sort of uber-tool that will forever change the world. (They do change things, but perhaps not entirely in the directions expected or to the degree proposed by the press).
Really, a lathe is far more "dangerous" in terms of weapons manufacture, but we're not hearing about it because it's a fairly ancient tool type.
If the 3D print files were able to make a functioning weapon on their own, I'd be much more concerned, but the types of plastic used make that generally unfeasible. And then we'd have a real question of what the ethics of posting a "gun file" would be.
Disclaimer: I own a 3D printer. (And a gun, but not with any printed parts).
Like these comments? Be sure to sound off in the comments! You could be in next week’s column.
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