Using a 555 timer and some electronic components can be made a pulse generator for servo motors.
Values of assembly components were chosen so that the pulse duration can be changed from 1 ms to 2 ms when the extra power and strength of the anode of D1 is increased from 2.7 k to 5.4 k. This variation of resistance is given by the rotation by about 75 ° to P1. Therefore, resistance R1 should be replaced in the scheme with a conductor.
It is possible to use all normal race, the 270 °, the potentiometer, which in this case,
should have a value of 2.7 k. Resistance R1 will be connected as shown in diagram.