Building The B9 Robot Torso

Here is some additional detail around how I configured my torso rotation position sensors. These sensors allow me to position the torso in 13 different positions around a 180 degree arc. This type of circuit is applicable to many applications.

IR- Position sensors mounted to a plastic semi circle that will be mounted inside the lazy-Susan.

Here it is in place. The sensors are around the back of the lazy-Susan. So the flag will rotate around the back to the right side when the torso rotates to the left.

That's my old motor. I ended up using a motor from Dewert. It had a smaller spike on startup. The large spike on the power line caused by the surplus Windshield Wiper motors from MECI were causing my Oopic Controller to get confused. Also, the noise on the line was getting into the Stereo Amplifier (even with a noise filter installed.) I'll have to update the photo with the new motor.

Close up of the sensors and the position flag mounted to the inside edge of the lazy-susan. This "flag" proved to be too small. Some times the flag would pass by the sensor before the Oopic would see it. I decided to go with a large flag arrangement. I could just widen the flag a little, but I decided to go even wider

Here you can see the larger flag (black horizontal stripe). It can cover three flags (plus some overhang) at once. This allowed me enough time to see the flag and stop the torso, while all three sensors are still covered. It also gave me some additional resolution. I can position the torso in between each of the 30 degree sensors (when only two flags are covered). This resulted in a 15 degree resolution which I needed at both extremes.

Position	Binary	Decimal #
Left 90 deg	10000001	129
Left 75 deg	10000011	131
Left 60 deg.	10000111	135
Left 45 deg.	10000110	134
Left 30 deg.	10001110	142
Left 15 deg.	10001100	140
Front 0 deg.	10011100	156
Right 15 deg.	10011000	152
Right 30 deg.	10111000	184
Right 45 deg.	10110000	176
Right 60 deg.	11110000	240
Right 75 deg.	11100000	224
Right 90 deg.	11000000	192

I have the 7 sensors wired to my Oopic controller so that each sensor is represented by a different position of an 8 bit word (10000000). The most significant bit is tied to a "1" since it is not used

So here's the "truth table" for the positioning sensors.

As an example, when the torso is facing forward, the sensors are showing "10011100". The first bit being the unused bit that is fixed at "1". Then you see the middle three sensors are covered by the flag so they come back a "1's". So "10011100" in binary is 156 in decimal.

When the robot is first powered I have it seek the middle position. I start it rotating in one direction and if I see "192" (far right) or "129" (far left) first, I know it going in the wrong direction so I reverse the direction until I see "156" (center).

Hope this makes sense.

In hind-sight, I should have tied the extra bit to "0". That would have made figuring out the binary and decimal numbers easier and would have made more sense. If I am back in inside sometime soon, I may do that and recode the program.

Torso Rotation Sensors