# Servo Motor Controller and Tester Circuit Using 555 IC

A tutorial on how to make a servo motor controller & tester circuit using 555 timer IC and a few other components. This circuit allows us to manually drive/control any servo motor by pressing buttons or by turning knob of a potentiometer.

## Components Required

• 555 Timer IC
• Servo Motor
• 1 PN Diode (I used 1N4148)
• 2 Momentary Push Button Switches
• Resistors: 220K, 56K, 10K
• Capacitor: 100nF
• (5-9)V Power Supply (Adapt to Servo voltage)

Note: If you wish to control the servo using potentiometer, use a 50K resistor in series with a 1K resistor instead of 56K, 10K resistors and push button switches. Refer to the circuit below for the exact arrangement.

## Circuit Diagram

This circuit uses two momentary push buttons: one to rotate the servo arm clockwise and the other to rotate the arm anti-clockwise.

If you wish to control the servo motor by turning the knob of a potentiometer, you need to make the connections as shown below:

## How This Circuit Works

Servo motors are controlled by using a PWM (Pulse Width Modulated) signal as their input. You may refer to this project: LED Dimmer and DC Motor Speed Controller Circuit Using PWM Technique for understanding how 555 timer IC can be used to generate PWM signal. It also explains how the ON time of each PWM pulse can be adjusted.

The position of the servo arm depends on the width of ON time (High pulse) of the input PWM signal. Generally, if we set the width of ON time to 1ms, the servo arm moves to 0 degree position. If we set the width of ON time to 3ms, the servo arm moves to 180 degree position. The width of OFF time (Low Pulse) is maintained constant at around 18ms.

In this circuit, 56K & 10k are used to alternate between two ON pulse widths corresponding to 0 degrees and 180 degrees. So clicking one button moves the servo arm to 0 degrees and the other moves the servo arm to 180 degrees.

## Applications

• For quick testing of servo motors
• For controlling servo motors using a physical reference (Like rotation of knob of the potentiometer)
• To automatically move servo arm left or right based on a physical trigger (Eg: Electronic door latch systems)

If you have any queries/suggestions, feel free to post them in the comments section of this video: Servo Motor Controller and Tester Circuit Using 555 IC