Electrical
There are several interacting electrical components to our
project. The issue of how these
components interact is discussed in more depth in the software section. In this section we treat each
electrical component as modular: each
component has certain input and it transforms those inputs into useful outputs.
Laser control:
The laser can do two things: it can fire, or it can turn as
a result of movement in the servo motors (either horizontally or vertically).
Firing the laser is controlled by the fire button on the
game board. This button acts as a
switch and it is connected to a voltage divider circuit. When the button is not pressed the
handyboard receives a signal of ~0V at digital input 15, when it is pressed the
handyboard receives a signal of 5V.
Two adjustable knobs (potentiometers) are connected to
analog ports 1 & 2. These
provide the signal that allows the human to control the angle of the
laser. As the schematic shows,
these potentiometers simply act as voltage dividers that provided an analog
signal to the handyboard between +5V and 0V. A 1 microFarad capacitor is added in parallel to act as
low-pass filter since the knob was observed to be electrically noisy.
The servo motors are connected directly to ports on the
handy-board. Their three wires
attach to +5V, signal, and ground at each port. The circuitry (and software) that transfers signals from the
knobs to the servo motors is internal to the handyboard.
Digital Logic:
Digital logic is necessary to control the LEDs (18) and to
receive the signals from the photoresistors(9) because there are more
components here than there are available input/output ports on the handyboard.
The first digital logic component is the encoder, which is
what picks up the signal from one of nine photoresistors on the board, encodes
it to a certain binary value, and then sends it to the handyboard. A 10:4
encoder, along with hex-inverters, was used in order to accomplish this task,
as the circuit diagram shows.
After the handyboard receives an input from the photoresistors,
it decides which LEDs to light up, and then sends a signal to the encoder
circuit so that a certain LED lights up.
Since the encoder is only capable of switching one LED on at a time,
flip-flops are necessary. The
flip-flops maintain an LED in it’s on state after then encoder turns on another
LED. As the circuit diagram above
shows, the decoder is used along with D flip-flops and J-K flip-flops.