Want to convert AC to DC? Here's a simple circuit that'll convert AC to DC
from a low voltage (9 to 18V) transformer.
Look real close at the little round bridge rectifier, at the top there'll be a plus symbol (+), that'll be the positive output terminal, and at the bottom there's a minus symbol (-) which is the DC Gnd for our circuits. The other two terminals on the sides will be the AC input. The large electrolytic capacitor will filter the output and it's polarized. The white stripe along the side of the capacitor is the negative, or Gnd, side, the unmarked side is the poisitive terminal. If it's connected backwards it'll draw lots of current and will probably explode.
This circuit will handle about an amp.
Now that we have a filtered DC supply, we need a well regulated 5 volt DC supply
for all our circuits involving microprocessors.
This device is rated a 1 amp continuously, but that assumes an infinite heatsink. Without a heatsink it'll get pretty hot with as little as a half anamp. All of the microprocessor circuits will draw just a couple of amps, The servo motors will draw around a half amp (500mA), but that's just a pulse of current for a couple of milliseconds and occurring every 20 milliseconds for an average current of only around 50 milliamps.
It's possible, with a number of servos running at the same time, that the pulses will occur simultaneously and might even draw enough current to cause the output of the regulator to fold, but probably wouldn't have time to overheat the device.
From an 18VDC supply the heat produced in the regulator is (18V-5V) * current, or 6.5 watts with a steady-state half amp. The same load with a 12VDC supply would be (12-5)*.5 or 3.5 watts. If you've ever touched a night-light with one of the little 7.5W Christmas tree bulbs you'll know how hot a few watts can be.
The bottom line is: Powering a few flasher kits an a half-dozen servos would probably be just fine, much more than that you'd probably be looking for a nice hefty 5 volt supply rated to at least a few amps. Most PC power supplies have 5 volt supplies rated over 10 amps and 12 volt supplies nearly that. (12 volt supplies are great for LEDs in buildings, street lights, etc. You can power a series string of LEDs with just one current limiting resistor.)