22-10-2016, 11:20 AM
1460460175-eee322project130906065523phpapp02.pptx (Size: 208.18 KB / Downloads: 8)
Theory
Dc motors are widely used in robotics for their small size and high energy output.
The typical DC motors operate on as few as 1.5 volts on up to 100 volts.
Roboticists often use motors that operate on 6 12 or 24 volts.
A low voltage(e.g.12 volts or less ) DC motor may draw from 100MA to several amps at stall depending on its design.
Main characteristics of DC Motors include: High Speed, Low Torque, Reversibility and Continuos Motion.
Let’s say the loop wire was arranged on a bearing so that it could freely rotate .What we need is some way of switching the current through the wire on each 180 degrees of rotation. We do this with a simple brush mechanism(FİG 14).In this case as the loop rotates to a vertical position you notice that at the end of wire leaves the switch contact. Under inertia,the loop continues to rotate until the other side of the loop strikes the right hand side contact and original loop contact makes contact with the left hand side brush.
The direction of rotation depends on:
The polarity of the battery (Power Source)
The stator is the stationary outside part of a motor. The rotor is the inner part which rotates. The ends of each wire set for a connecting set is called a commutator. The torque of a motor is the rotary force produced on its output shaft.
When a motor is stalled it is producing the max. amount of torque that it can produce. Hence the torque rating is usually taken when the motor has stalled and is called the stall torque
Motors that draw more current will deliver more power.
The speed of the output shaft is directly proportional with the applied voltage.
So the voltage drop on load (motor) was the thing we consider throgh all the design procedure.
Where to Use This Circuit & Suggestions
This circuit can easily be used for fan applications and anywhere we need dc motor to rotate permanently.
A switch can be used to switch between “turbo” mode in which we want more power and torque (overspeeding) from the motor where we need performance. (Which is directly connecting to 12V by a switch.)
For overspeeding there must be calculation done how much time it will be overspeeded and how much the motor can handle.
For fan applications temperature sensors would be beneficial. (Closed loop control system)
This circuit can also be used for lighting. Since there is a net voltage drop of about 6 volts a group of LED can be directly controlled. Small light bulbs can be directly handled by this circuit but for higher ranges need to increase voltage.
Can be used to drive small conveyor belts in 2 directions and with dimmer would be able to handle both directional control and speed control.
It is also possible to use this circuit for any robotic application where directional control is needed with speed control such as RC helicopters’ or aircrafts’ propellers.