Robots are one of the most popular toys to hit the shelves
in 2001. While there's no revolutionary machinery involved in
their design, they do combine several familiar technologies in
an innovative way. The main hook of these toys is their gaming
element: Players collect special cards to activate different
fighting moves and increase their bot's power level.
In this edition of HowStuffWorks,
we'll look at the various components that make a Rumble Robot
work. As you'll see, the basic elements in a Rumble Robot are
simply modified versions of common electronic devices we use
on a daily basis.
Bring to Light
Most remote control toys are
operated by a radio
transmitter. When you move the controls, the transmitter
sends a radio signal, at a particular frequency, to a radio
receiver inside the toy. The radio signal includes a
distinctive set of electromagnetic pulses, which represents a
particular command. The toy recognizes this command and
carries it out. (See How Radio
Controlled Toys Work for details.)
Inside a Rumble Robot
Rumble Robots operate on a similar system, but they use
infrared light instead of radio waves. An infrared
remote control is like a miniature Morse code lamp. It
transmits messages by flashing a small light-emitting
diode (LED) in a distinctive pattern of long flashes and
short flashes. The infrared light emitted by the LED is
invisible to our eyes, but not to the robot's light-sensitive
panel. The sensor picks up the signal and deciphers the
The LED from a Rumble Robot
This is the same principle used in standard television
remote controls. In fact, the Rumble Robot controller
looks a lot like a TV remote on the inside. The plastic
controller housing contains:
Rumble Robots (as well as
most other modern electronics) use printed circuit
boards. A printed circuit board is a thin piece of
fiberglass with thin copper "wires" etched onto its surface.
These wires connect a number of electrical components together
in a complex circuit.
- Three batteries
- A light-emitting diode
- Two circuit boards
The circuit boards in a Rumble Robot controller include:
When you move the plastic pads
on the controller, they push down on the circuit board's
buttons. The buttons are just pieces of rubber that hold small
conductive plates. Pressing the button pushes the conductive
metal piece up against a contact point on the circuit board.
Normally, each contact point is an open section of the
circuit between the battery and the integrated circuit. In
other words, the etched wires do not connect, so the electric
current cannot flow to the microchip. Pressing the conductive
plate down on the wires closes the circuit -- the current
flows across the plate from one wire to the next, and moves on
to the microchip.
When you press down on the buttons in the
controller, they complete a
The integrated circuit sorts out which buttons are
depressed, generates an appropriate command signal and passes
it onto a transistor. The transistor amplifies the signal and
activates the infrared light. The controller will keep sending
the signal as long as buttons are depressed.
In the next section, we'll see what happens when this
signal reaches the robot's light sensor.
In the last section we saw
that the Rumble Robot controller transmits commands via
infrared light. Each controller has an A setting and a B
setting. When you switch between the settings, the microchip
changes the flash pattern of the infrared signal.
The robot has A and B settings as well. When you switch the
robot from A to B, it will ignore the A-pattern signals, but
will register the B pattern signals. If you have two robots of
the same model, you have to set one on B and one on A.
Otherwise, one controller would activate both of them.
Different models use different patterns, to make battling
The robot's infrared
The central element of the infrared receiver is a small
photocell, an electrical component that responds to
light. Photocells are one widespread application of the
photoelectric effect, the emission of electrons by
certain materials in response to certain frequencies of light.
The typical photocell consists of a light-sensitive semiconductor
layer, sandwiched between two electrodes. The battery sends a
constant electrical current across the two electrodes, whether
the photocell is exposed to light or not. When you expose the
photocell to the right kind of light, the boost in electrons
amplifies the current flowing across the electrons. If the
light flashes on and off, the current will increase and
decrease in the same pattern. In this way, a photocell
translates the light signal into an electrical signal (see How Solar
Cells Work for more on this process).
The central circuit board in the Rumble
The electrical signal passes on to the robot's central
integrated circuit. Based on the digital pattern of this
signal, the integrated circuit carries out certain actions,
such as moving forward, turning or throwing a punch. In the
next section, we'll look at the components involved in these
Fight the Good Fight
Just like a
radio-controlled car, a Rumble Robot has four wheels, which
are powered by electric
motors. As you can see in the picture below, the Rumble
Robot has two driving motors, which spin a series of gears to move
the robots wheels. These motors are housed in the bottom half
of the robot.
The robot's wheels are driven by two electric
When the integrated circuit receives the appropriate
signal, it sends an electric current to one or both of the
motors. Each motor can spin in two directions, depending on
the direction of the current. (See How Electric
Motors Work for details.)
By reversing the current flowing to either motor, the
integrated circuit can change the robot's direction. If both
motors receive positive current, all wheels will spin the same
way and the robot will move forward. If both receive negative
current, the robot will move backward. If one motor receives
positive current and the other receives negative current, the
wheels on each side will spin in opposite directions, and the
robot will turn. If the currents are then switched for both
motors, the robot will turn in the opposite direction.
The robot has a third motor in its head that moves the arms
back and forth. As you can see in the picture below, this
punching mechanism consists of two rack-and-pinion
gears. The motor turns the central gear, which turns a
connected gear that moves the racks.
The punching gear mechanism in Lug
In this design, the base of each gear is notched on two
sides; that is, it has two sections with teeth separated by
two smooth sections. The sections with teeth engage the teeth
of the racks, which are attached to the robot's arms. When the
teeth are engaged, the gear will slide the rack (and the arm)
backward. When the gear revolves around to the smooth section,
it releases the rack. The racks are spring-loaded, so they
punch forward on release.
This is the particular mechanism at work in "Lug Nut."
Other Rumble Robots have different punching styles, with
different gear arrangements, but the basic elements are fairly
The object of a Rumble Robot game is to get your robot to
land effective blows against your opponent's robot. In the
next section, we'll see how Rumble Robots register these hits.
A Very Palpable Hit
In a Rumble Robot match,
the object is to score hits on the opposing bots. There are
three ways to score hits:
- Hit the robot's terminate switch - Rumble Robots
have a small bumper switch just behind the head. When the
robot is pushed against the wall, or when another robot hits
it from behind, the switch is pushed closed. This completes
a circuit, which tells the integrated controller a hit has
The terminate switch in a Rumble Robot: At
the base of the switch, there is a small metal spring
surrounded by a larger metal spring. When you press the
switch, the two springs come into contact, completing a
circuit. Closing this circuit tells the integrated
circuit that the robot's switch has been
- Tip the robot over - Each robot model has an
internal gravity switch. The gravity switch has a
pendulum element, which closes an electrical connection when
you tilt the robot more than 60 degrees on its side. If one
robot knocks another one over, the switch registers a hit.
- Drain the robot's power points with your laser -
The laser is actually just a light-emitting diode, like the
one in the controller. When you pull the fire trigger, the
integrated circuit activates this light. Each robot also has
a photocell on its base, which works the same way as the one
on its head. This laser LED and photocell are calibrated to
a different frequency than the controller transmitter and
receiver, so the two systems don't interfere with one
another. When the laser receiver picks up the infrared from
another robots light beam, it tells the integrated circuit
that the robot has been hit.
The robot's "laser unit": An infrared LED to
shoot light beams and a photocell to receive
To use the laser, enable the punching mechanism or increase
a robot's power, players have to collect the right cards. In
the next section, we'll see how Rumble Robots read these
Play Your Cards Right
The main thing that
sets Rumble Robots apart from other remote control toys are
the power cards. Each Rumble Robot comes with a set of
power cards, and additional cards are available in separate
Rumble Robots come with a deck of power
By sliding the right sequence of cards through a slot in
the robot's head, players can activate the robot's laser
defense, punching mechanism, speed and power points.
Just like the infrared detector photocell, the scanner
sensor translates the light pattern into an electrical signal.
The robot's integrated circuit reads this signal and enables
the new move or boosts the robot's power level. When the robot
is defeated, or the power cuts off, the integrated circuit is
reset. It has to "learn" the moves all over again.
With the popularity of Rumble Robots, we're sure to see
many similar fighting toys in the future. Like Rumble Robots,
these toys will combine a standard remote control system with
a host of interactive features. To learn more about Rumble
Robots and similar machines, check out the links on the next