These materials can be used for both
the schools competition and the maze-solving competition.
This is the drive train assembly used
in the DASH series of Micromice. It consists of two
4.5-12V DC motors with worm gear drive to the wheels. The
wheels are 32mm diameter fitted with O-ring tyres.
Unlike the DASH FREE drive
train, the motor spindles are fitted with
photo-interrupters giving 8 index positions. A
phototransistor and infra-red LED are fitted for each
The overall width of the drive train
is approximately 80mm.
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This is the motor used in our drive
trains. It is a Mabuchi RC-280SA-20120 motor giving
29g.cm torque at 6400 rpm taking 0.57A from a 6V supply
at maximum efficiency. The stall torque from a 6V supply
is 175g.cm at a current of 2.85A.
This is a powerful beast. You should
be able to make mice with a top speed over 1 metre/second
two 75mm long 2mm
diameter steel shafts,
one 10 by 6 mm worm
one 6 by 6mm worm gear
one 16 tooth 9mm dia.
one 30 tooth 16 mm
one 42 tooth 22 mm
one 60 tooth 31mm dia.
one16 mm dia. 30/10
tooth compound gear
one 22 mm dia. 42/10
tooth compound gear.
All the gears push fit
onto the shafts. You will need two sets; one for each
side of your mouse.
We use these sensors
in the DASH FREE and DASH micromice.
The photo IC drives
one or more LEDs with pulsed light and responds only to
light that is phase-locked to these pulses. It is very
tolerant of sunshine and fluorescent lights. DASH
micromice work well even with full sunlight and shadows
on the maze.
The photo-IC drives an
LED directly and only needs this and a decoupling
capacitor to give a logic output. We add a second LED to
show whether the output is high or low to help when
positioning the sensor.
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This is a bright,
narrow angle visible-red LED that we use for
Micromice. It gives 1000
mcd at 20mA with a viewing angle of 8 degrees. A flat on
the body denotes the cathode.
We use a single LED
with each Hamamatsu S4282-11 photo-IC in DASH
FREE. Where we need more sensing range we buffer the
photo-IC with a power transistor driving one or two LEDs.
We get area coverage
with multiple LEDs all driven via a transistor from one
photo IC. Separate limiting resistors tailor the
brightness of each LED to suit its distance from the
sensor. DASH-2 has up to 4 LEDs with one photo IC
to sense that it is too close to a wall. This arrangement
avoids "dead spots".
We use visible LEDs
instead of infra-red as it is much easier to see where
the light is going. A small amount of stray light can
completely wreck a sensing set-up. We control stray light
with a combination of Tipp-Ex and grommets!
This is a simple
solution for the battery holding problem. These battery
boxes can hold two AA size cells. We use them in DASH
FREE, for carrying the 4 nicads that supply the
power. Some people may want an extra one of these holders
to run their DASH FREE at higher voltage for more