whatever you wanted to rotate with it. Even better than
that, the kit includes a motorMate, which is a small
cylindrical plastic piece that connects to the motor shaft on
one end and has perpendicular slots on the other end that
make a plus shape.
The slots make it super easy to attach things to the
motor, and the flexible plastic means that you can push
things into the slots that will actually be held on pretty well
even without any adhesive. Perhaps the most exciting
aspect of the motorMate is the fact that the slots happen
to be the perfect shape to fit a LEGO axle.
The servo module includes a small servo connected by
wires to the circuit board portion of the module sporting
the magnetic connectors. The servo module comes with a
variety of horns in the shapes of arms and wheels, with
small mounting holes. One of our favorite design features
of the servo module is the mode changing switch. The
servo module can run in two modes: swing and turn.
In the swing mode, the servo will sweep back and
forth over its entire range of motion. If you hook it up to
an input like a dimmer, turning the knob will change the
speed of the sweep. In the turn mode, the servo will
change position in accordance with input instead of
continuously sweeping back and forth.
The presence of two different modes was cool, but our
favorite part of this feature is actually how you switch
between the modes — via a small low profile switch on the
module board (complete with helpful labels). A simple
switch might seem like a silly thing to be excited about, but
we like this solution a lot better than what we’ve seen in
other kits. In other kits when you needed to change the
mode of something, it’s often achieved by changing the
position of a small jumper. We don’t like the jumpers
because they are a piece that completely separates from
the board and is likely to get misplaced and/or lost. The DC
motor module also has the same kind of switch, and that
one changes the direction of the motor.
For our robotic guardian, we envisioned a bot with a
simple drive train, some arms to flail around menacingly,
and lights and sounds to intimidate any wannabe present
destroyer. With the snap-together littleBits, we were able to
put together the basic circuit behind the robot for testing
before having to ensconce it in the robot body.
At the start of the circuit was the power module, the
button, the inverter, and the LED that made up the pressure
plate device. We tacked the Arduino module on the end of
that, then ran a long wire to the rest of the modules that
would comprise the robot. We connected the wire to a wire
branch module. One of the branches led to the DC motor,
another led to a servo module, a third led to a buzzer, and
then to the final servo module.
We had the servos and motor all connected to the
same output port on the Arduino board to allow us to have
the longest tether between the robot and pressure plate.
That meant the servos and motor would all activate
together, but we didn’t really need much control over the
SERVO 12.2014 73
STUDYING THE SERVO MODULE.
BODGING TOGETHER A DRIVE TRAIN.
THE PUG DEFENDER CIRCUIT.