REVIVING AN ANDROBOT BOB: Part 4
on or almost 22. 5 degrees
off in either direction. To
get a better idea of where
North really is, BOB can
turn until either the East or
West bits toggle on. From
there, he can keep track
of how far he has to turn
until the opposite side
toggles on. By splitting the
difference and turning
back, he should be fairly
close to North. To keep
track of the turning, we can
either time the movement or
use the encoders on the main drive motors. This is a good
way to start combining the data from multiple sensors and
improve BOB’s view of the world.
BOB is also going to get some rudimentary sound level
detection. It will give BOB an idea of what the ambient
sound levels are. This is done using a simple condenser
microphone and an amplifier based on an LM386 chip. The
microphone came out of an old cordless phone I had. The
output of the amplifier is connected to the analog 6 input
on the Handy Board. Nothing fancy here. We can watch the
value on this port to look for drastic changes, which could
be things like hand claps, etc.
There are two more sensors that I haven’t yet had a
chance to connect. These are the two original IR sensors
that I found inside BOB’s head. One seems to be an IR
motion sensor and the other an IR heat sensor. These two
infrared sensors were supposed to be a human detector.
The original Androbot flyer for BOB says “Infrared sensors,
attuned to the frequency of human body heat, enable BOB
to locate human beings.” Another section says, “His
infrared sensors then ‘recognize’ people (while
differentiating between human body temperature,
fireplace heat, and incandescent light heat).” Wow! That
sounds like it would be really slick to get wired up and
working again.
I still need to figure out exactly how these sensors were
supposed to work. I started by gathering up all the datasheets
for the chips used on the board. With those in hand, I am
tracing out the schematic for
the hand wired circuit board
in the head. It is taking a
while to sort out and I hope
to get some sort of data
from them again. In practice,
I don’t know how well they
ever worked.
Years ago, I had talked
to an Androbot engineer
who remembered BOB and
said that part was always
troublesome. It was a bit too Schematic of amplifier for
sensitive and supposedly condenser microphone.
Audio amp (component side).
Audio amp (solder side).
could tell the difference between a white and black file
cabinet. Seeing the difference in radiated heat, he would
stop and think it was a person. It would have been pretty
funny to see BOB trying to strike up a conversation with a
file cabinet.
HOW DID COLUMBUS DO IT?
As a test to make sure I had the Dinsmore compass module
wired up and working correctly, I used a real compass as a
sanity check to make sure they agreed. Before I could do this, I
had to buy a compass since the one I had was lost over the
years. You’d think just buying a compass would be an easy task
— Not! I was shocked at the poor quality and choices available.
The first one I picked up didn’t seem to move as freely as I
would have expected so I questioned just how accurate it
would be. I didn’t need to be within a degree or two but at least
wanted to be in the ballpark. To my dismay, when I looked at all
of the compasses sitting on the shelf most of them all pointed in
different directions! Needless to say, I tried another store that
carried more brands. It seemed that everywhere I checked
many of the compasses were off, too. Finally, I found several
different compasses from various manufacturers that all agreed
and picked one of them. During the trip home, the compass
agreed with the one in my car and also with the direction of the
local roads. It makes me wonder just how many people
purchase a compass without checking them and assume they
are okay. The important point here is to double-check things
like this before you buy and not to assume they will be right. It is
critical if you are using it as a reference to check other devices.
SERVO 05.2008 61
