20.1 PCB BOARDA printed circuit board, or PCB, is carried to mechanically support and electrically connect electronic components by means of conductive paths, traces, or signal traces etched into from copper sheets laminated on a non-conductive substrate. It is also called printed wiring board (PWB) or etched wiring board. Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices. A PCB filled with electronic components is called a printed circuit assembly (PCA), printed circuit assembly or PCB assembly (PCBA). In informal usage, the term "PCB" is used for both bare and assembled boards, with context clarifying the meaning. Alternatives to PCBs include wire wrapping and point-to-point construction. PCBs must initially be designed and laid out, but become cheaper, faster to manufacture, and potentially more reliable for high-volume production since PCB production and soldering can be automated. Much of the electronics industry's PCB design, assembly, and quality control needs are defined by standards published by the IPC organization. PCBs are inexpensive and can be very reliable. They require much more setup effort and a higher initial cost than wirewound or point-to-point built circuits, but are much cheaper and faster for high volume production. Many of the electronics industry's printed circuit board design, assembly, and quality control needs are defined by standards published by the IPC organization. Printed circuit boards are primarily an insulating material used as a base into which conductive strips are printed. The base material is usually fiberglass and the conductive connections are usually copper and are made by an etching process. The main PCB is in the middle of the paper......the input pulse width is the same. Depending on the pulse width we get a different position. The diagram shows some control signal pulses for a typical servo and the position it will rotate to in response to the pulse width. There is another element in the signal that also requires timing accuracy. The frequency of the signal or its refresh rate. Not only do we have to send the impulse, but we have to keep sending them for as long as we want the motor to be in that position. Most of the time, 50 Hz is good. This means we need to send the high pulse 50 times per second. A servo will only rotate 180 degrees until we modify it for continuous rotation. One interesting thing that comes out of this modification is that you get a speed control feature from it.23.3 APPLICATIONS Used in RC aircraft design Fixed angle movement