In this Instructable I demonstrate how to build a sample rotator using Erector set parts and littleBits. The sample rotator, or media rotator "is a common piece of standard laboratory equipment that is used for continuous mixing of lab samples, for example for slowly reacting or dissolving components" (1). I've broken the process of building the rotator into six steps. First, build the rotator base. Then build the support to prop up the rotator base. Next build what I call the "windmill," or the arms where the centrifuge tubes containing the samples are attached. I then demonstrate different methods for attaching the centrifuge tubes to the rotator and how to build the circuit to drive the littleBits motor module. Finally, I show the adjustable power supply wall-wart I use to power my littleBits projects.

Update: My littleBits sample rotator was featured on Dangerous Prototypes!

littleBits are color coded electronic modules that connect together magnetically to create simple electronic circuits. They are designed for ages 8 and up so hobbyists, designers, makers, and artists can add light, sound, and motion to their crafts and projects. Since they connect up magnetically (no need for circuit boards, breadboards, or solder), you can’t accidentally connect them the wrong way. With littleBits you can quickly build electronic circuits in a matter of minutes.

The color coded modules are divided into four categories. Blue, for power, currently includes three modules—the power module to which you connect a 9 volt battery, a coin battery module, and a USB power module. Pink for “input,” currently includes almost two dozen modules such as push buttons, switches, potentiometers, light sensors, and so on. Orange, for “wire,” includes several wires, branching connectors, and logic gates. Finally, the green “output” components include a little over a dozen modules such as motors, a fan, a buzzer, several kinds of LEDs, and a speaker.

An example of a circuit might be the blue power module connected to a green motor module. Switch on the power switch located on the power module and the motor spins. (2)

(1) Source: http://www.teklalabs.org/sample-rotator
(2) http://littlebits.cc/bits/dc-motor

Step 1: Build the Rotator Base

In the littleBits Base Kit, the motor module comes with an adapter for a Lego cross-axle so you can add motion to a Lego project. There does not seem to be a littleBits adapter as of this writing for other construction toys such as K’nex or Erector. I decide to see if I could use the littBits motor with Erector set parts to build a simple motorized project for your home laboratory.

The sample rotator uses a worm drive. I didn't need to change the gear ratio--the motor module is built for torque, not speed. But I was hesitant to mount the rotator mechanism directly onto the littleBits motor axle. Perhaps the axle could take the weight of up to four 50 ml centrifuge tubes. The gear box on the motor module, however, has dainty little gears that remind me of the gears in an analog watch so I was concerned whether these gears could withstand the stresses of such a load.

The diameter of the littleBits motor module axle is smaller than an Erector set axle so you may need to use two set screws to center the axle of the motor module. In the second picture you'll notice I included two set screws to mount the worm drive on the littleBits motor axle.

Parts needed:

4 3 by 5 hole flat plates
2 3 by 5 hole flat plates
Note: The yellow Erector base plates are flimsy, so I had to reinforce them with the two silver Steel Tec 3 by 5 hole flat plates. The holes on the Steel Tec plates are larger in diameter and don't line up well with Erector parts. The yellow plates simply serve to line up the holes properly.
1 5 by 7 hole base plate
2 3 by 5 hole base plates
1 3 by 5 by 3 hole double angle strip
2 Angle brackets
1 Worm gear (with 2 set screws)
1 Pinion gear
1 Axle
4 Large screws
4 Plastic collars (spacers)
10 Small screws
10 Nuts
1 Standard hex wrench
1 set screw hex wrench
1 littBits motor module
1 littleBits wire module

good one
good one
<p>This is the most <strong>practical </strong>application of littleBits I have seen yet! Awesome job, and thanks for the share.</p>