Servo-Pulse Generator

0I Circuits for the generation of control pulses for servo apparatus remain popular, which seems a good enough reason to present another one. The popularity of servo control is en- hanced by the low price of servo motors, and the fact that they can be used for a variety of applications. The present design is geared to stand-alone use of the servo. Simplicity of the circuit was the first design consideration, and it seemed reasonable, therefore, to base it on the well-known 555 IC. Unfortunately, this chip has the property, in its standard configuration, of producting pulse trains with a duty factor* of 50% or greater. This is so, because the charging time constant is always greater than the discharge one, since during charging the discharge resistance is in series with the charge resistance. Servos, on the other hand, require pulse trains with duty factors well below 50%. Ideally, the pulses should have a width of 1- 2 ms, and the pulse repetition frequency - prf - should be...