Welcome to DIY Haunts, Dispatch #4
Welcome to the DIY Haunts
contest newsletter #4! Hopefully everyone is working hard on their creations. While you still have plenty of time -- the deadline is midnight, November 2nd -- you'll want to keep an eye on the clock because you'll need every moment to produce a prizewinning awesomeness! If you're following along with the Spooky Fun Tombstone Project, this issue of the newsletter has us exploring how to control the servo, as well as how to wire up and install the LEDs. If you're running into problems, either with the tombstone project or your own build idea, we encourage you to visit our DIY Haunts Forum
, where you can share your progress and ask questions. Or maybe you're done and ready to submit your entry? Hot dog! Go to http://makezine.com/contests/diyhaunts.csp and enter the particulars of your project.
—John Baichtal and Gareth Branwyn
back to top More Betwitching Inspiration
If you're still looking for ideas, check out this excellent animatronic hand project on Instructables. It's a simple concept, with tubing serving as both the fingers and the joints, with string acting as tendons. Imagine it in a full zombie limb getup, or repurposed as a diabolical spider. Add a couple of servos to manipulate the strings, as well as some lighting and audio effects, and you're golden!
back to top What is a Transistor?
Let's continue to work on our Spooky Fun Tombstone. If you're building the project along with us, we're going to be wiring up the LEDs using resistors and a transistor. But hold on, you may ask, what exactly is a transistor?
A transistor is essentially a switch that allows a small amount of electricity passing through one set of terminals to control a larger amount of electricity passing through another set. This lets a relatively low-power device like an Arduino, for example, control electricity at levels that would ordinarily fry it.
We'll be using the common 2N2222 transistor that we spec'd for the optional DIY Haunts Prop Kit from Jameco Electronics. In the tombstone project, we won't be controlling vast amounts of electricity, but we're stretching the Arduino's capabilities a bit, so the transistor will help.
back to top Wiring Up the LEDs
Next, we'll wire up six LEDs using three of our resistors and one transistor. Check out the schematic above -- click on it to enlarge. We're looking at two strings of LEDs, with a resistor protecting each string and the third resistor looking out for the transistor (the 2N2222 in the schematic.) We'll make use of the Arduino's Vin port to output 9V, and control the flow with a PWM digital port.
To install the LEDs on the tombstone, first decide how you'll like the LEDs to be arranged. For ours, we wanted them spread out evenly along one side of the split. The best way to attach them to the tombstone is simply to make a hole in the foam and shove in the LEDs, then connect them either directly or with wires. Make sure to get the LEDs' polarity right — the voltage goes in the long lead and out the short lead.
back to top How to Control a Servo with an Arduino
Next let's get the servo ready to go. What is a servo? It's basically a gearmotor, but it has circuitry built into it that allows it to be controllable via special signals or computer code. Do you want to turn the motor's shaft precisely 15 degrees? You can do it through your Arduino board.
There's a great tutorial on Arduino.cc that explains how you'll be able to control the servo. First, you'll have to attach it. Plug the red wire into the port marked 5V on your Arduino, connect the black wire to Gnd, and the yellow to Analog 0. But how can you do this given that the end of the servo wire is a plastic plug? That's where the header pins and solderless breadboard from your DIY Haunts Prop Kit
come in. First, break off three header pins from the strip and use them to connect the servo wires to the bread board, and then connect the Arduino to the breadboard with the wires. If you're having a hard time visualizing it, the tutorial above has a great photo.
Your servo is now connected. If you want to play around with programming it, the above tutorial contains some sample code. Otherwise, our sixth newsletter will show you how to put everything together, and that includes programming the Arduino!
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