Page 171 - Build Your Own Combat Robot

Build Your Own Combat Robot
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Like the IFI Robotics Victor, the Vantec draws its 5-volt logic power supply
from the motor drive power and uses opto-isolators to prevent electrical noise
from feeding back into the radio receiver. The low-voltage regulator circuit auto-
matically draws power from whichever battery input is at the highest voltage. The
negative sides of both batteries are connected together internally, but the positive
sides are not, and the Vantec can be used to independently control two motors of
different voltages if desired.
Vantec also makes a product known as the “Bully” power servo amplifier that
accepts a standard from an R/C receiver to control a large motor just as if it were a
very large servo. The signal is fed into the “Bully,” along with a potentiometer in-
put. The potentiometer is used to monitor the actual rotational position of a
geartrain’s output shaft or an actuator arm’s position. The Bully can be used to
control an arm where the actual position control is required, such as leg positions
in walking robots.
The biggest challenge with the Vantec speed controller might be dealing with
the company. Lead times on a Vantec controller can be weeks or months in times
of high demand, and repair times on a damaged controller sent back to the company
are similar, so you might want to keep these lead times in mind when testing and
competing. You may find that most of their models are a bit expensive, but this
company is one good example of “getting what you paid for”—its products are
well built. Vantec stands by its products and has a reasonable “repair deposit”
policy that allows users who have “fried” the Vantec products for whatever reason
to have them repaired at a significant cost savings over purchasing a completely
new product.

The 4QD Speed Controller

For British robots, the traditional choice for the speed controller has been the
4QD motor controller board, and many American combat robots have success-
fully used the 4QD controllers (www.4qd.co.uk). 4QD is a British company that
makes a wide range of motor controller boards for electric vehicles, floor-clean-
ers, golf carts, scooters, and other industrial and robotic uses. With voltages of up
to 48 volts and current levels of up to 320 amps, the largest 4QD controllers can
handle higher power levels more than any of the Innovation First or Vantec models.
Table 7-3 shows a specification list of several 4QD controllers.

Model Number Voltage Range Continuous Current, Amps Max Current, Amps
4QD-150 24, 36, 48 120 160
4QD-200 24, 36, 48 150 210
Pro-120 12, 24, 36, 48 30 115

TABLE 7-3 4QD Electronic Speed Controllers