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ENERGY CONTROL AND SOFTWARE 169
suitable than others for battery-powered robots. It’s time to review power regulation and,
in the bargain, we can take note of regulation techniques that are good for robots.
The central problem to be solved in power regulation is to prepare an untamed energy
source to provide tame power for the robot. Certainly, the type of tame power needed
by the robot will vary. In some instances, the robot’s circuitry can use unregulated Direct
Current (DC) or Alternating Current (AC) to power components like motors or sole-
noids. But in most cases, the robot’s components will need well-regulated DC power.
This type of power is generally specified by the voltage, the acceptable voltage range,
the current available, and the level of ripple that can be tolerated. For some 5-volt DC
supplies, the specifications might read: “5V - 0.25V, 5A, 25 mv pp ripple.” This is a
power supply that can deliver 5 amps into the robot at a voltage between 4.75 and 5.25
volts with only 25 millivolts of ripple noise. The ripple noise is often 60 Hz of noise (on
supplies driven by the AC power) or a higher frequency from a switching action that
will be discussed shortly.
Unstated specifications for a power regulator include the following:
Efficiency Although our example power supply might deliver 25 watts into the
robot (5V 5A), it might require a feeder wattage of 40 watts to do so. That
would make its efficiency 25/40 62.5 percent. The power regulator alone wastes
37.5 percent of the energy.
Emissions Power supplies generate interference (electrical noise and radiation),
which propagates out all the power connections and through the air. Since com-
pliance with regulatory bodies is often required (as mentioned in Chapter 4), we
must pay attention to the power supply as part of this effort.

Types of Regulators Power supply regulators are available in many forms, including
the following:

Linear regulators Linear regulators are an older technology that is well char-
acterized. One or more large transistors take the unregulated power at a higher
voltage (Vin) in one side and deliver regulated power at a lower voltage (Vout) out
the other side. By and large, since the current flows linearly through the power
supply, Efficiency Vout/Vin.
Generally, the larger the difference between Vout and Vin, the better the power
supply, keeping noise spikes on Vin from getting to Vout. Unfortunately, this low-
ers the efficiency. Also, more cooling may be necessary; the power supply tran-
sistors may need larger heatsinks. Linear regulators are relatively simple and can
be reduced to a single three-terminal component with connections for Vin, Vout,
and Ground. They do not generate significant electrical interference, but they are
not very efficient as a rule.