08-16-2017, 10:25 PM
optocoupler interface microcontroller and energy meter
Abstract
The present system of energy billing in India is error prone and also time and labour consuming. Errors get
introduced at every stage of energy billing like errors with electro-mechanical meters, human errors while noting down the meter reading and error while processing the paid bills and the due bills. There are many cases where the bill is paid and then is shown as a due amount in the next bill. There is no proper way to know the consumer's maximum demand, usage details, losses in the lines, and power theft. The remedy for this drawback is overcome by APEMS (Advanced
Prepaid Energy Metering System).
The GSM module provides a mode of communication between the user/meter and the EB Station. This will enable the
user to recharge his/her electricity account from home. This will also enable the user to carry his/her electricity account with him, eliminating the need to set up a new account every time the user changes homes. The GSM module will also get real time electricity rates and enable the utility to keep a check on electricity theft. This can also be applied in institutions/companies for creating awareness for saving energy among employees.
WHAT IS OPTOCOUPLER
optocoupler is also called optoisolator, photocoupler and optical isolator. It is used to provide isolation between two electrical circuits. It is a electrical component which is used to transmit input signal by using light energy signals. It provides electrical coupling between input and output through light waves. Its main purpose is to avoid changing in voltages at output side to appearing at input side. Higher voltage fluctuations may damage input side electrical components.
OPTOCOUPLER WORKING
optocoupler consists of a LED which converts input electrical signal into light energy signal. Photo transistor at the output side detects light signal and turned on when LED light falls on it. In this way its output becomes low and high according to input signal and LED lights.
TYPES OF OPTOCOUPLERS
Many types of optocouplers are available in market according to their rating and design like fast optical isolator, analog optoisolator and linear.Rating depends on output voltage drive capacity of optoisolator. The mostly used optoisolator for maximum output voltage are 30 volt, 70 volt and 80 volt. You can purchase from market according to your requirement. They can easily operate between temperature range of 70 C to 150 C. Name of mostly used optocouplers are given below:
4N25, 4N26
PC817 and many others
So there are many types of optocouplers available. It is impossible for me to show you how interface all the these optical isolators with microcontrollers. I will choose one and show you how to interface it with microcontroller. Procedure for all others will remain same. Like if you know how to interface lcd with avr microcontroller, you can also easily interface it with pic, 8051 and arm controller .
APPLICATIONS OF OPTOISOLATOR
In some applications we use it to separate to electronics circuits. For example dc motor produce back emf with sudden change in input voltages. They are used to remove such effect. They are also widely used in communication devices likes modems etc.
In this article, i will show how to use PC817 optocoupler. because it is most popular among engineering students and easily available in market.
PC817 OPTOCOUPLER
It consists of an LED and photo transistor. It comes in 4 pin DIP package. It can provide input/output voltage isolation uputo 5KV. Input current is 5mA and collector to emitter voltage can be 80 volt. It can be used for input output isolation of controllers. PC817 interfacing circuits diagram are shown below.
PC817 OPTOCOUPLER INTERFACING WITH PIC
Interfacing circuit diagram is shown below. All the connections are self explanatory. But if you still feel any issue le me know with your comments. 24 volt dc motor is used as a load. PC817 is used to provide isolation between 5 volt and 24 volt circuit. Pin number 5 of port is used as output pin as a control signal.