Imagine a special motor that can turn to very exact positions, this circuit is its brain.
It tells the motor how far to turn by sending tiny bursts of electricity.
The length of these bursts tells the motor how far to move.
The circuit listens to what you tell it to do like turning a robot arm and sends the right bursts to the motor.
Circuit Working:
Parts List:
| Category | Component | Quantity | Details |
|---|---|---|---|
| Resistors | 390k | 1 | 1/4 watt |
| Potentiometers | 10k | 2 | |
| 470Ω | 1 | ||
| Capacitors | Ceramic C1 | 1 | 0.15µF |
| Ceramic C2 | 1 | 0.1µF | |
| Semiconductors | IC | 1 | 7555 |
| Diode | 1 | 1N4148 | |
| Actuators | Servo Motor | 1 |
This is a basic design for a servo motor controller with a pulse generator.
It utilizes the CMOS IC 7555 in the astable mode to produce pulses for driving the servo motor.
The circuit can be adjusted to generate pulses of sufficient length.
A servo is a small device with an output shaft that can be positioned to specific angular positions by sending it a coded signal.
As long as the coded signal is present on the input line the servo will maintain the angular position of the shaft.
The angular position is determined by the duration of a pulse applied to the control wire, known as pulse coded modulation.
The servo typically requires a pulse every 20 milliseconds 0.02 seconds.
The length of the pulse determines how far the motor turns.
Normally, a 1.5 millisecond pulse will turn the motor to the 90 degree position, known as the neutral position.
A shorter pulse will turn the shaft closer to 0 degrees, while a longer pulse will turn it closer to 180 degrees.
The circuit is designed to provide control signals to the servo.
IC1 is configured as an astable multivibrator, generating pulses for the servos operation.
The 10K potentiometer VR2 along with resistors R1 and capacitor C1 determines the high and low times of the pulses.
As VR2 is variable, the high time varies from 2.07ms to 1.03ms.
The low time remains constant at 40.5ms.
Adjusting VR1 allows for precise timing.
VR3 adjusts the control voltage from 1.6V to the control pin 5 of IC1.
Alternatively, a control voltage can be supplied externally, in which case VR3 is omitted.
The control voltage can be provided by a variable power supply with an output of 0 to 10V.
This control voltage dictates the position of the servo motor connected to the output.
When the control voltage changes the servo moves to the new position corresponding to the new control voltage value.
At 0 volts, the servo remains at one end, while at 10V it goes to the other end.
A control voltage of 5V keeps the servo in the center position.
Formulas:
The IC 7555 may be set up in a number of ways, one of which is as a generator of pulse width modulation PWM for controlling a servo motors position.
Here is a general formula and circuit design for one of these:
PWM or pulse width modulation:
The location of the servo motors shaft will be determined by the PWM signal produced by the IC 7555.
The following is an approximation of the formula for the PWM signals frequency (f) and duty cycle D:
f = 1.44 / (RA+2RB) * C
D = RB / RA+2RB
where,
- C is the timing capacitor attached to the IC 7555 and RA and RB are resistors.
It is possible to fine tune the PWM frequency and duty cycle, which has a direct impact on the position or speed control of a servo motor, by adjusting RA and RB.
Remember:
Verify that the operating voltage and current requirements of the servo motor align with the circuit design.
First, test the circuit on a breadboard to see that it works properly.
Then, based on the particular servo motor response and performance needs, modify the component values (potentiometers, capacitors, and resistors) as needed.
This guide offers a fundamental structure for creating a basic circuit for a servo motor controller that makes use of the IC 7555 and related parts.
Performance testing and individual application requirements may call for modifications and adjustments.
How to Build:
Below mentioned are the process of how to build a Simple Servo Motor Controller Circuit:
- Connect pin 4 and pin 8 of the IC to the positive terminal of the power supply.
- Connect pin 1 to ground of the IC to the negative terminal of the power supply.
- Connect pin 2 and pin 6 together.
- Connect pin 3 to one terminal of servo motor.
- Connect pin 7 directly to VR2 10k pot.
- Connect the other terminal of R1 to pin 6.
- Connect pin 6 to the junction of R1 390Ω resistor and C1 0.15uF capacitor.
- Connect pin 5 to one terminal of VR3 470Ω pot.
- Connect the other terminal of VR3 pot 470Ω to the negative terminal of the power supply.
- Connect the capacitor C2 0.1µF to pin 5 and the ground.
- Connect the positive terminal of the power supply to the positive terminal of the servo motor.
- Connect the negative terminal of the power supply to the negative terminal of the servo motor.
- Connect the pin 3 to the servo motor of control input.
Note:
- Once the circuit is assembled, adjust VR1, VR2 and VR3 to obtain the desired pulse width and control voltage for the servo motor.
Conclusion:
To conclude, a servo motor controller circuit is a crucial component in systems requiring precise control over the position of a servo motor.
By generating specific pulse widths based on input signals the circuit can accurately position the servo motors shaft.
This capability makes servo motor controller circuits invaluable in robotics, automation and other applications where precise angular positioning is necessary.