About:
The creation of this robot was inspired by my desire to keep a watch on my house while I'm out for business.
A normal camera turret is just too stationary; it locks you into one perspective. With Peabody, however, the
camera is free to move where ever you like! And in addition to having a moving camera turret, it has 2
all-terrain tires each driven by power drill motors so you can go anywhere in the house. It is also
equipped with a twin bulb spotlight for night operation and a 90db attention buzzer to signal danger.
Base Controller:
This base acts as the interface between Peabody and a computer. Primarily just a breakout box for all the
wires leading to the robot, it also contains the power supply that runs it. The base also has a little bit
of combinational logic so that I can turn it's primary power supply or an additional power outlet on and
off. This is accomplished by monitoring the status pins from the serial port and controlling them from my
custom software. The Tx and Rx pins are simply passed right through to the terminal block for other devices
to have an easy connection point.
Motor Control
Probably one of the most noteworthy features on this robot is how the motors are controlled. On almost
all my other projects, motors are run by relays opening and closing. This limits the user to just 3 states
of operation. Forward, Reverse, and Stop. That's it, no speed variance, and that often leads to jerky
motions. Peabody is different. Instead of using relays for both controlling current direction and for
engaging / disengaging power to the motors, it only uses relays for current direction. The actual running
of the motors is controlled by Pulse Width Modulation (PWM). This allows me to instruct the robot to speed
up or slow down, ultimately giving me a much smoother maneuverability, especially when it comes to turning.
Another benefit to starting and stopping the motors with a solid state device is that it eliminates arcing.
With relays, you will always have the full available power across your relay contacts weather the motors are
stopped or moving. This causes an arc inside the relays every time the contact state is changed. This is not
only bad for the life of the relay, the EM noise produced by the spark often times disrupts the operation of
the onboard processor which usually causes the whole thing to reset!
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PWM and Relays Working Together for Motor Control
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Additional Pictures:
Peabody 2.0
This wood bodied version was implimented because the metal base was actually too heavy to give it good mobility. This one is not only lighter and
more agile, it also has a 5:1 gear ratio between the motors and gears for even more torque.
