01-04-2014, 10:03 AM
MOTORISED SCREW JACK
MOTORISED SCREW.doc (Size: 310 KB / Downloads: 39)
INTRODUCTION
A screw jack is a device used to fully or partially lift a vehicle or other object off the ground. Depending on their size, these devices can be used to raise the corner of a vehicle, or to lift it several feet in the air so workers can access the bottom of the vehicle. Screw jacks are often found in machine shops, auto repair facilities and in the automotive racing industry. Many vehicles also have a screw jack included with the spare tire kit, so drivers can repair a flat tire more easily. Very large screw jack systems are even used to lift houses for foundation repair or replacement.
DESCRIPTION
In this project we are presenting the prototype of motorized screw jack. To design its structure aluminum sheet is used. It is a combination of bed, cover, platform, a large screw jack etc.
Bed, it is actually the base of the screw jack over which whole structure is designed. Two slant plates of aluminum are used to connect the base with the lifting platform. And the width of platform is equal to the distance between these two plates (you can see it in picture also).
Now to make motion in the screw so that lifting can be done high torque motor is used which is connected with it by the help of coupler.
Here to control the DC Motor we have used the remote to control the motion of the jack.
DC MOTORS:
Basically, the motors can be categorized into two parts, AC and DC. The basic principle of operation is almost same. In any electric motor, the operation is based on simple electromagnetism. A current carrying conductor generates a magnetic field; when this is placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and the strength of the external magnetic field. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current carrying conductor and an external magnetic field to generate rotational motion.
DC Motors can be classified as:
Externally Excited DC Motor:
This type of DC motor is constructed such that the field is not connected to the armature. This type of DC motor is not normally used
Shunt DC Motor:
The motor is called a "shunt" motor because the field is in parallel, or "shunts" the armature. This type of motor runs practically constant speed, regardless of the load. It is the type generally used in commercial practice and is usually recommended where starting conditions are not usually severs. Speed of the shunt-wound motors may be regulated in two ways: first, by inserting resistance in series with the armature, thus decreasing speed: and second, by inserting resistance in the field circuit, the speed will vary with each change in load: in the latter, the speed is practically constant for any setting of the controller. A shunt wound motor has a high-resistance field winding connected in parallel with the armature. It responds to increased load by trying to maintain its speed and this leads to an increase in armature current. This makes it unsuitable for widely-varying loads, which may lead to overheating.
Series DC Motor:
The motor field windings for a series motor are in series with the armature.
This type of motor speed varies automatically with the load, increasing as the load decreases. Use of series motor is generally limited to case where a heavy power demand is necessary to bring the machine up to speed, as in the case of certain elevator and hoist installations, for steel cars, etc. Series-wound motors should never be used where the motor can be started without load, since they will race to a dangerous degree. A series wound motor has a low-resistance field winding connected in series with the armature. It responds to increased load by slowing down and this reduces the armature current and minimizes the risk of overheating.
DC MOTOR DRIVER:
As the most of the PORT of MCU or any other controlling ICs are not powerful enough to drive DC motors directly so we need some kind of drivers. A very easy and safe is to use popular L293D chips. It is a 16 PIN chip. The pin configuration is shown in the diagram.
This chip is designed to control 2 DC motors. There are 2 INPUT and 2 OUTPUT pins for each motor. The diagram with proper connection is shown in the next diagram. The ‘RA3’ and ‘RA2’ pins are used to control the motor one and ‘RA0’ and ‘RA1’ pins are used to control motor B. Pin1 and Pin9 are enable pins. If these pins are not connected to +5V, then both the drivers will remain deactivated until they are enabled. Whatever power supply we provide at pin 8 and pin 16, this supply will go to both motors. Hence we have to be careful about the rating of motors while connecting the power supply to this IC using this IC.
The behavior of both motors are similar are exactly similar. Here the table describes the controlling method of one motor; same is applicable for other motor.
RF MODULE 434 MHz/315MHz:
This is the transmitter and receiver pair. This receiver type is good for data rates up to 4800bps and will only work with the 434/315MHz transmitter. Multiple 434/315MHz receivers can listen to one 434/315MHz transmitter. Only one 434/315MHz transmitter will work within the same location. The receiver is operated at 5V. The transmitter operates from 2-12V. The higher the Voltage, the greater is the range.
We have used these modules extensively and have been very impressed with their ease of use and direct interface to an MCU. The theory of operation is very simple. What the transmitter ‘sees’ on its data pin is what the receiver outputs on its data pin. If you can configure the UART module on any controller, you have an instant wireless data connection. Usually HT12E and HT12D are used with transmitter and receiver modules respectively. Data rates are limited to 4800bps. The typical range is 500ft for open area.