Simple Servo Driver

One of the perks of my job at the University is that much of our development work carries directly over into my hobby of flying radio controlled model planes. While building a robot may not seem related to airplanes, many of the components are the same and the theory of operation of the electronics is likewise almost identical. One of our needs in the robotics class is the ability to control the movement of a servo without having the servo attached to a standard radio receiver. While some of the 'BOT designs do use a typical radio transmitter and receiver employed by the radio control hobbiest, the vast majority of student projects rely on an inexpensive programmable microprocessor. However, when "hacking" servos for full rotation or when testing a servo for operation, it is more efficient to use a simple controller rather than having to find a functioning 'BOT or locate a transmitter/receiver to control the servo (student prototyping labs are not always the most organized places). While servo drivers are commercially available, I felt we could fabricate them locally at a fraction of the cost and use the design process as a teaching tool in a digital electronics project -- for students to effectively program their microprocessors, they need to know what type of signal input is required to control servo movement.

The circuitry needed to emulate a signal produced by a radio control transmitter/receiver is deceptively simple and the parts count for the circuit is amazingly low -- however, please note that this design will NOT control the newer digital servos. Given the simplicity, I usually refer to the design as "paper plane science" as opposed to "rocket science".

The construction of this driver is covered in two files. First is a Power Point presentation that contains the circuit schematic, a board mask and a stuffing diagram (a mouse click will page thru the presentation). The second file is an instruction sheet with some assembly and calibration information.

Schematics and Diagrams

Assembly and Calibration Instructions

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