FIGURE 6. Bumper detail.
across the terminals. Fortunately, only my pride was hurt.
Figure 3 shows the battery wiring.
While my controller would run happily off the battery, I
decided to isolate the controller power from the motor
power system to avoid spikes and noise. Automotive motors
can generate voltage spikes and RF noise that is potentially
harmful or disruptive to more sensitive electronics. I used a
fuse block and PWM (pulse width modulation) units to
control the power to the motors. Take a look at Figure 4.
Figure 4 shows the wiring of the fuse box and PWM
units. The wiring scheme is red for V+, black for ground,
and white for the fuse protected 12V. The three wires
(black/red/white) are for the control signals to the PWM
units. For this robot, I used older IFI Victor PWM units but
less expensive PWM units or even relays would suffice for
this application. Outside of the controller, the most
expensive components were the motors and motor
controllers. I used two kinds of sensors for this robot: an
ultrasonic range finder (Figure 5) and two bump sensors.
Getting the bumpers to work correctly took a couple of
tries. I finally came up with the design shown in Figure 6A
and 6B. I used some 1” wood dowel, some aluminum
tubing, and pipe insulation to fashion the bumpers. The
sweeper I use is pretty light in weight, so some additional
ballast is needed so it doesn’t tip over, especially when
FIGURE 7A. Pan tilt webcam (re-tasked Altoid boxes)
44 SERVO 11.2010
adding weight to the top. I’m starting to add a remote
telepresence functionality to GoPHR, as well.
So far, my software development has been limited. I
have been using an older VEX controller. I was hoping to
get my greasy grubby hands on one of the new Qwerk type
controllers being developed in stealth mode. Alternatively, a
laptop plus a Serializer board would have the necessary
processing power to run as a telerobot. It would be nice to
run this robot as a remote website (a movable webcam).
That way, I can get the house vacuumed in case I am
running late. I could call up from my hands-free mobile and
tell GoPHR to get GoING. Alternatively, I can just ditch the
sweeper and find out what the cat has been up to.
I am beginning to work on a manipulator for simple
tasks. I plan to evolve this manipulator by adding a degree
of freedom at a time. My first goal is to add a spatula,
because then I can have a robot that can both sweep the
floor and flip burgers (which appear to be the career
choices I have left during this down economy). Another
planned enhancement is a docking charging station.
Depending on my choice of motors, materials, and PWM
units, the cost of a GoPHR platform (sans controller) will be
in the $200-$500 range.
For additional information and updates, check out my
website at http://federman.best.vwh.net. SV
FIGURE 7B. A Skype call to 3CPO.