DC motor control using SCR
DC motor control with SCR
Introduction
In this project we will on/off the DC motor using TV remote . we are using RC5 standard of remote to control it. We are using Philips TV remote.
Its a low cost control system. We will press keys 1,2,3—- and will control devices and stepper motor. We are using TSOP1738 in this project. It works on 38 KHz. It give serial data at pin no 14(p3.3) of 89s51 microcontroller. We are using microcontroller 8051 which we studied in 8085 microprocessor. We can do programming of microcontroller to control in C or assembly or other language. We are doing programming in assembly because its easy.89s51 is Atmel company’s IC. Its also low cost IC
| Philips RC-5 Protocol |
The RC-5 code from Philips is possibly the most used protocol by hobbyists, probably because of the wide availability of cheap remote controls.
The protocol is well defined for different device types ensuring compatibility with your whole entertainment system. Lately Philips started using a new protocol called RC-6 which has more features.
| Features |
- 5 bit address and 6 bit command length (7 command bits for RC5X)
- Bi-phase coding (aka Manchester coding)
- Carrier frequency of 36kHz
- Constant bit time of 1.778ms (64 cycles of 36 kHz)
- Manufacturer Philips
| Modulation |
The protocol uses bi-phase modulation (or so-called Manchester coding) of a 36kHz IR carrier frequency. All bits are of equal length of 1.778ms in this protocol, with half of the bit time filled with a burst of the 36kHz carrier and the other half being idle. A logical zero is represented by a burst in the first half of the bit time. A logical one is represented by a burst in the second half of the bit time. The pulse/pause ratio of the 36kHz carrier frequency is 1/3 or 1/4 which reduces power consumption.
| Protocol |
The drawing below shows a typical pulse train of an RC-5 message. This example transmits command $35 to address $05.
The first two pulses are the start pulses, and are both logical “1”. Please note that half a bit time is elapsed before the receiver will notice the real start of the message.
Extended RC-5 uses only one start bit. Bit S2 is transformed to command bit 6, providing for a total of 7 command bits. The value of S2 must be inverted to get the 7th command bit though!
The 3rd bit is a toggle bit. This bit is inverted every time a key is released and pressed again. This way the receiver can distinguish between a key that remains down, or is pressed repeatedly.
The next 5 bits represent the IR device address, which is sent with MSB first. The address is followed by a 6 bit command, again sent with MSB first.
A message consists of a total of 14 bits, which adds up to a total duration of 25 ms. Sometimes a message may appear to be shorter because the first half of the start bit S1 remains idle. And if the last bit of the message is a logic “0” the last half bit of the message is idle too.
As long as a key remains down the message will be repeated every 114ms. The toggle bit will retain the same logical level during all of these repeated messages. It is up to the receiver software to interpret this auto repeat feature.
PS: I had rather a big error on this page for quite some time. For some mysterious reason the LSB and MSB of the address and command were reversed. I can recall correcting this error before, but somehow an old version of the description must have sneaked its way up to the internet again.
| Pre-defined Commands |
Philips has created a beautiful list of “standardized” commands. This ensures the compatibility between devices from the same brand.
A very nice feature, often to be missed with other brands, is the fact that most devices are available twice in the table allowing you to have 2 VCRs stacked on top of each other without having trouble addressing only one of them with your remote control.
BLOCK DIAGRAM
| SOCKETS |
| h- BRIDGE |
| MicrocontrollerDriving Circuit89S52 |
Working :
Sensor:-In this project we will connect three pin
Sensor have three pins one VCC, ground and out. It works on 38Khz. Signal decoded by 89s52 at pin no p3.3. output of microntroller will be connected at port1.ports 1st and 2nd pin is connected to isolator circuit. Isolators are optocoupler pc 817. pc 817 is 4 pin ic. In PC 817 contain LED and phototransistors in built. When led work then transistor work. Negative of in built LED in pc 817 is connected to microcontroller. Positive of microcntroller is connected to VCC 5v. 3 pin of PC 817 is connected to ground. Output of PC 817 is pin 4 . 4.7k ohm is connected to VCC. Output of pin 4 is connect to bases of transistors npn and pnp. H bridge circuit contain transistors. Hbridage circuit work as current and voltage amplifier.
Bases of transistors connected to output of pc817. and emitters are output to motors. We are using DC geared motors..
DC geared motors are of 100 RPM and 12 v.
It take 50 to 100 mA current.
In relay drive drive circuit we will control the 12v Dc relay. It can control device of 220v AC-7Ampere. Its called cube type relay in market. Many qualities available in the market. It will have five pins.
Two for coil ,three for switch.
For relay drive circuit we will take active low output from microcntroller . when pulse come from microcntroller. It will go to BC 558. collector of BC 558 is connected to npn transistors . npn transistor will give low signal to relay coil. Other end of relay is already connected to VCC 12v. when current will flow from relay then connections will change . in this way relay will work as a switch.
Figure 6 – Schem WELCOME TO THE WORLD OF THE MICROCONTROLLERS.
Look around. Notice the smart “intelligent” systems? Be it the T.V, washing machines, video games, telephones, automobiles, aero planes, power systems, or any application having a LED or a LCD as a user interface, the control is likely to be in the hands of a micro controller!
Measure and control, that’s where the micro controller is at its best.
Micro controllers are here to stay. Going by the current trend, it is obvious that micro controllers will be playing bigger and bigger roles in the different activities of our lives.
These embedded chips are very small, but are designed to replace components much bigger and bulky In size. They process information very intelligently and efficiently. They sense the environment around them. The signals they gather are tuned into digital data that streams through tributaries of circuit lines at the speed of light. Inside the microprocessor collates and calculators. The software has middling intelligence. Then in a split second, the processed streams are shoved out.
Applications:
Machine control
Water pump control
Boilers control- it can be used to control boiler ,furnaces and remote high temperature equpments
Safety devices- we are adding power failure option in project that’s why we can use this project to protect losses due to power failure.
