52 SERVO 06.2015
magnet based construction technique: Flick a switch on a
light sensor module and you have a light-seeking robot.
Flick the same switch and convert your photovore (light
eater or light seeker) into a photophobe (fearing light or
darkness seeker) robot.
All of the required modules — including the two light
sensor Bits — snap together and rest comfortably on top of
the ActoBitty channel. A completely “wired up” ActoBits is
shown in Figure 1. The total assembly time for building
your own will be roughly one hour.
You will need seven Bits along with the Actobotics
ActoBitty kit for building ActoBits:
littleBits Modules -
• Power p1 [plus the requisite 9V battery]
• Fork w7
• ( 2) Light sensor i13
• ( 2) Proto w9
• (Optional) Light wire o16
• The ActoBitty kit #637146
NOTE: Except for the unusual proto Bit (w9), each
of the littleBits modules can be individually found in
the littleBits online store, or they are included inside
various popular littleBits kits or module collections
(e.g., Space Kit, Deluxe Kit, etc.). The proto Bit is a
little harder to find. Luckily, two proto modules are
included inside the littleBits Hardware Development
Kit (HDK 680-0005). Begin your assembly of ActoBits
by building the ActoBitty kit. This is a straightforward
intuitive build with only two minor deviations from the
online assembly instructions.
First of all, route the motor wires through the
large holes on the channel’s side before you mount the
motors. Running the wires through these two rear holes
will streamline your final robot design and ease the
connection of the motors to the littleBits control system, as
well as help keep the wires away from the spinning wheels.
The second modification to the ActoBitty kit build isn’t
near as dramatic as the first — the simple removal of the
AA battery holder. Power for this entire project will be
supplied via the 9V littleBits power module instead.
Whoa there! Every sharp-eyed robot reader must be
wondering how this 9V power supply is able to both drive
the two ActoBitty motors and operate the light sensor
control system. Technically, you’re correct. This design
should support two commercial motor drivers or — at the
very least — two minimal H-bridge motor drivers for
isolating the control system. Yes, these drivers could be
added to the littleBits circuit, but the robot can still operate
without them. Performance does suffer in this driverless
configuration, but neither the motors nor the control
circuitry will be damaged.
Advanced users might opt to build a couple of H-bridge motor drivers on a littleBits perf module (w29), then
substitute this module for the proto modules. A perf
module is included along with the proto modules inside the
Throwing caution to the wind, the ActoBitty motors
are plugged into the littleBits proto modules — one motor
per module. Each connection is made by removing the
jumper blocks from the three sets of pin headers located
between the screw terminals, and plugging the motor’s red
and black wires into the SIG signal pin and the GND
ground pin. Figure 2 shows this attachment.
Connecting both motors in this fashion converts
ActoBits into a spinning “head bot.” In other words, the
robot simply turns on its wheels, pointing its sensors
towards light or darkness depending on how the light
sensor module switch is set (i.e., light or dark). If you want
ActoBits to drive towards light or darkness, then you must
reverse the polarity of one motor. The simplest way to do
Figure 1. The power
supply nests inside the
ActoBitty channel, while
the littleBits control
hardware neatly seats
on top of the channel.
The black post jutting
out from the bottom of
the ActoBitty is one of
the kit's battery
Figure 2. Use two proto modules (w9) for connecting the
ActoBitty motors to the littleBits control hardware.