WEEK 10
Output Devices
How the week started
Input device week did give an idea about how these devices work. So the output devices have been chosen after discussing with my instructor Sibin and Saheen.
How the week ended
Week 10’s Assignment
Group assignment:
- Measure the power consumption of an output device.
- Document your work on the group work page and reflect on your individual page what you learned.
Individual assignment:
- Add an output device to a microcontroller board you’ve designed and program it to do something.
Why I need an Output Device?
This week we are using devices that interact with us. In my final project I need the sun to move in a curved path. This movement of the light is linked to the time in the RTC. The RTC tells time to the microcontroller, then the light moves. This is the output part.
To do this movement I need a motor. There are stepper motors and servo motors.
My understanding of Output devices
How Electric Motors Work
What is a Motor?
An electric motor converts electrical energy into mechanical energy, usually as rotational motion. There are two types of electric motors based on the type of current they use, the coil design, and the magnetic field created.
‖ An Introduction to Motors ‖ What is an Eelctric Motor? ‖ ‖ Youtube - How does an Electric Motor work? ‖
DC motors
The DC motor works by direct current flowing to the commutator. The commutator is connected to the electromagnets. The electromagnets rotate as the polarity changes due to the current. The electromagnets are surrounded by permanent magnets. The rotation happens because of continuous switching of current direction through the commutator and brushes.
DC motors are of two types based on the commutation they use: brushed motor and brushless motor.
Brushed DC Motor
Dc Motors that use mechanical commutation , that is they use brushes as the mechanical contact. The current is delivered as the rotor turns, the brushes make contact with the commutor. These brushes stay in contact with the rotating part (Shaft).
BLDC - Brushless DC Motor
Dc Motors that use elctronic commutation are called Brushless DC motors (BLDC). As it operates without brushes it has high efficiency, long life, and precise control when compared to brushed dc motor.
- ESC (electronic speed controller) electronically commutates the motor by controlling the flow of current in the stator’s winding based on feedback from hall sensors.
- Hall sensor gives real time rotor position feedback, allowing the electronic controller to switch the stator coil current (commutation) at the precise moment for smooth, efficient operation.
Stepper Motor
Stepper motors are a type of brushless motors. It is rotated by direct current. It is an electronic motor which rotates in steps rather than an continuous rotation motion. Since it rotates in steps it has larger number of magnetic poles.
Stepper motors have a relatively large torque, especially at low speeds .
Stepper Motor + Driver
Stepper motors work based on the number of steps required for the motor to rotate. The number of steps can be called input impulses. The driver rotates the motor based on the number of steps it is instructed to move. The driver does not know the exact position of the motor, it only follows the given steps. Therefore, if there are any unexpected changes in the load or the device, the change in position of the rotation is not known by the driver.
‖ Stepper Motors ‖ ‖ Brushless DC Motors vs. Stepper Motors 1 ‖ ‖ Brushless DC Motors vs. Stepper Motors 2 ‖
Servo Motor
Servo motors can roate to a specific angle or position. It has built-in position feedback mechanism therfore allowing precise control over angular velocity and position of motor. the servo motors are usually DC motors but somethimes AC motors. Servo motors are usually rated in kg/cm (kilogram per centimetre), Exanmple:
Stepper motors have a relatively large torque, especially at low speeds .
‖ Servo Motor Basics ‖ servo control of stepper motors ‖ Understanding Basics of Servo Motor Working ‖
Servo motors are usually rated in kg/cm (kilogram per centimetre). This means the torque the motor can provide at a certain distance from the shaft. For example, a 25 kg·cm servo means it can support 25 kg at 1 cm from the shaft. If the distance increases to 2 cm, it can support 12.5 kg. At 3 cm, it can support around 6.25 kg.
If the motor is unable to move due to excess weight, the current consumption increases.
Servo - Closed-loop feedback system
The servo motor control system continuously compares the input signal (desired position) with the feedback signal (actual position) obtained from the position sensor. When there's a difference, the control circuit generates an error signal that drives the motor until the desired position is reached. This closed-loop feedback system ensures precise positioning accuracy.
MG90S Micro Servo Motor – 180° Rotation
- Weight: 13.4 g
- Dimensions: 22.5 x 12 x 35.5 mm (approx.)
- Stall torque: 1.8 kgf·cm (4.8 V), 2.2 kgf·cm (6 V)
- Operating speed: 0.1 s/60° (4.8 V), 0.08 s/60° (6 V)
- Operating voltage: 4.8 V to 6.0 V
- Dead band width: 5 µs
